Megasquirt-II Sequencer™ Wiring

DRAFT DRAFT DRAFT DRAFT DRAFT DRAFT DRAFT DRAFT

There are a number of tools and techniques you will need to wire MS-II Sequencer™ to your vehicle. You will also need some specialized knowledge. We will try to present an overview of everything you need here (if you have questions, ask them on the forums at www.microsquirt.com):

Tools:

Supplies:

Of course you will also need a PC computer to run the tuning software. Any computer that can run Windows 98 or higher (i.e., WinMe, WinXP, WinVista) will work. Ideally the computer will have a serial port (9-pin male connector), but many USB/Serial adapters have been used successfully. A laptop computer is easiest to use in the vehicle, of course, and cheap older laptops with Win98+ and a serial port are commonly available at low cost.

Wiring Procedure

NOTE: The wire labeled "Vref" is the +5V voltage source for the MAP sensor and the TPS sensor. This wire only connects to these components (and possibly the LEDs, if used), so be very careful to not connect this directly to ground or (worse) +12V battery. Bad things will occur if you mis-wire this one - double check your work.

When wiring up a vehicle, we recommend performing this in discrete and deliberate stages - this is how to approach this:

  1. You may wish to use the MS-II Sequencer™ access board, which can simplify the wiring for many installations.

  2. Always make sure the dangling wires on the MS-II Sequencer™ harness are not touching each other or any metal (ground return path). Next, wire up all of the sensors (TPS, EGO, coolant, intake air temp, MAP) and the signal return grounds (use the sensor ground return wire for these). Then hook up the main ground wires to the engine block and the switched +12V for the +12V lead. Check again to make sure the remaining dangling wires (which includes the outputs - you have not hooked them up yet) are insulated from each other and anything else - tape these if need be.

  3. Hook up the laptop and run MegaTune and establish communications - remember that with the latest MS-II embedded code (V2.881 and later) you need to set the "ECU Type" to MS-II Sequencer™ the first time you run (click the "burn to ECU" button for this and any other change to stick). Until you set the ECU Type, all the other parameters will be grayed out.

  4. Let MegaTune and the MS-II Sequencer™ just run for a while and talk to each other, at least for several minutes. If there are any communications burps/hiccups, this is the time to find them out and correct (it's a nice, clean electrical environment at this point). Do not worry about the MS-II Sequencer™ sucking down the vehicle battery, its current draw is around 40 milliamps, so it is a very small load - the dome light above your head draws many times more current. This is also a good time to get familiar with MegaTune - set up the number of cylinders, REQ_FUEL, ignition trigger type, etc. - and, maybe save off a MSQ or two, just to get the feel for how it all works. Read Configuring MegaSquirt-II for information on configuring MS-II Sequencer™ and MegaTune. You should also: If this works as expected (the sensor values look good, the TPS values aren't backwards, you have set the correct MAP sensor type, etc.), you are in great shape, and you are potentially minutes away from a running engine.

  5. Also, in this state, with no ignition or injectors hooked up (and no fuel pump active), turn over the starter motor with the MS-II Sequencer™ turned on and MegaTune running. This is a big current draw and if there are grounding issues you will see the sensor readings jump all over the place - if so then check your engine-to-battery-to-chassis grounds (see the sticky on this). Less of an influence but perhaps more fun is to turn on the windshield wipers, heater fan, headlights, and even blow the horn - each of these can produce noise on the +12V feed and it is better to find this out now so you can rectify instead of tracking down, say, a random tach glitch that is really caused by battery feed noise - it happens.

  6. Next, hook up the tach input source, and check for tach signal with MegaTune with the starter cranking. If you are using EDIS, GM DIS, or HEI module it is often better to test this along with the outputs (next step).

  7. Finally, hook up the fuel pump relay, injectors, and ignition. And then start it up (they always start right up, or at least do something), tweak the tune, and drive away! Read Tuning MegaSquirt-II for information on tuning.

For each circuit, you will need to:

  1. Choose the order of circuits you will work on. Generally, this should be:
    1. Power and ground circuits. Completing this step will let you power up MS-II Sequencer™ EFI controller, and test the connection to MegaTune on your tuning laptop.
    2. Sensors:
      • Coolant and Intake Air Temperature sensors (CLT and IAT),
      • Throttle Position Sensor (TPS),
      • Exhaust Gas Oxygen (EGO, aka O2) sensor (if used),
      • Manifold Absolute Pressure (MAP) sensor.
    3. Actuator and Injector Outputs: These include:
      • Fuel Pump,
      • Fast Idle (if used),
      • Ignition control module (if used),
      • Injectors.
    4. Ignition Inputs and Outputs:
      • Ignition Inputs ("tach" signal(s)),
      • Ignition Outputs (coils or ignition module driver(s))
    (Many of these are broken out separately from the main wiring diagram below to make it easier to follow.)
  2. For each item in your list, identify the wires you need to connect from the list and wiring diagram below and your vehicle wiring diagram.
  3. For each wire, crimp or solder the connection:
  4. Slide the heat shrink tubing over the connection, center it over the connection, then shrink it into place with a heat source.
  5. Verify that you have made the correct connection(s) at each step.
  6. After each step, test the function of the unit. For example, you can see if:

AMPseal 35 pin Connectors

Each of the two AMPseal connectors has 35 pins, numbered in rows from 1-2, 13-23, and 24 to 35. They are numbers from left to right as viewed looking in to the connector on MS-II Sequencer™. These numbers are also imprinted in the connector itself, if you look carefully.

You may have to put the harness ends of the wiring looms together by inserting the wires into the connector, etc.. The best instructions are Ampseal's, which you can read in a PDF file here: A35_harness_assemble.pdf.

The two Ampseal connectors are identical. One is at the end of the case marked "RED", the other is at the end of the case marked "GREEN". Most of the inputs and secondary outputs come out the "GREEN" Ampseal connector, and this is wired very similarly to MicroSquirt®. The 8 injector and 8 ignition outputs come out on the "RED" Ampseal connector.

"GREEN" Ampseal:

Wiring the "GREEN" Ampseal connector of the MS-II Sequencer™ to the external harness is much the same as with MicroSquirt® (www.microsquirt.info/uswiring.htm). The only difference is that the two injector (INJ1 and INJ2) and ignition (IGN and IGN2) wires on the harness are now the idle IAC stepper outputs. You use the same sensors, etc.

PinNameFunctionHarness Wire Color(s)
(main/stripe)
DRAFT
Pin112 Volt SupplyThis connects to a switched 12 Volt supply. Use the ignition switch to control a relay that provides 12 volts to both the MS-II Sequencer™ and the injectors.Red
Pin2CAN HighThis is one of two Controller Area Network (CAN) communications lines, used to communicate with MegaSquirt peripherals.Blue/Yellow
Pin3CAN LowThis is one of two Controller Area Network (CAN) communications lines, used to communicate with MegaSquirt peripherals.Blue/Red
Pin4VRIN2+Second ignition input signal (Input 2) for a cam position sensor or second crank sensor with the Dual Spark option.Brown/White
Pin5N/CNot Usedn/a
Pin6Flex FuelFor input from a ethanol Flex Fuel sensor.Purple/White
Pin7FIDLEThis is the output for controlling an ON/OFF style FIdle or a PWM style IAC (usually found on Fords). You uses either a stepper type IAC, or a FIdle (on/off) or PWM style idle valve.Green
Pin8FUEL PUMPThis output controls a fuel pump relay by providing a ground when the fuel pump should be running. It cannot control a fuel pump directly.Purple
Pin9IAC 1BStepper idle air controller lead for coil 1, pin B. This are typically used on GM applications, among others. See MS-II™ Idle Air Control for more details.Green
Pin10IAC 1AStepper idle air controller lead for coil 1, pin A. This are typically used on GM applications, among others. See MS-II™ Idle Air Control for more details.Blue
Pin11IAC 2AStepper idle air controller lead for coil 2, pin A. This are typically used on GM applications, among others. See MS-II™ Idle Air Control for more details.White/Red
Pin12IAC 2BStepper idle air controller lead for coil 2, pin B. This are typically used on GM applications, among others. See MS-II™ Idle Air Control for more details.White
Pin13SERIAL RxThis pin is used to receive data from the laptop computer serial port (usually a DB9 or DB25). It is connected to Pin3 on a DB9 connector (Pin2 on a DB25) to plug into your laptop/notebook computer.Red (pre-wired to jack)
Pin14SERIAL TxThis pin is used to receive data from the laptop computer serial port (usually a DB9 or DB25). It is connected to Pin2 on a DB9 connector (Pin3 on a DB25) to plug into your laptop/notebook computer.Orange (pre-wired to jack)
Pin15BOOTLOADERThis pin is grounded to enter bootloader mode, which allows you to update the embedded code in MS-II Sequencer™'s "MicroSquirt®" processor. This is the processor that uses the standard code shared with MS-II™ and MicroSquirt®. You can connect this lead to a switch, with the other side of the switch connected to ground. When you close the switch and reboot MS-II Sequencer™ EFI controller, you will be in bootloader mode. (On beta units, this lead should be tried to Vref when not actively using the bootloader.)Purple/Black
Pin16ACCEL LEDThis is the supply for an 'acceleration indicator LED'. You connect the cathode (short lead) of and LED (light emitting diode) to this wire. The longer lead of the LED you connect to a 330 Ohm resistor, then connect the other side of the resistor to the Vref wire (5 Volts). Be certain that Vref will not be grounded or connected to 12 Volts. Or you could use some other voltage source beside Vref. For example, you could use the battery supply voltage (nominally 12 Volts) as long as you increase the current limiting resistor value to 1K Ohms (to keep the current within limits). The LED will then light whenever accel enrichment is in effect.Yellow/Black
Pin17WARM-UP LEDThis is the supply for an 'warm-up indicator LED'. You connect the cathode (short lead) of and LED (light emitting diode) to this wire. The longer lead of the LED you connect to a 330 Ohm resistor, then connect the other side of the resistor to the Vref wire (5 Volts). Be certain that Vref will not be grounded or connected to 12 Volts. Or you could use some other voltage source beside Vref. For example, you could use the battery supply voltage (nominally 12 Volts) as long as you increase the current limiting resistor value to 1K Ohms (to keep the current within limits). The LED will then light whenever warm-up enrichment is in effect.Yellow/White
Pin18N/C (ground)Not Usedn/a
Pin19SERIAL GROUNDSerial communications dedicated ground.Green (pre-wired to jack)
Pin20SENSOR GROUNDThis is a dedicated sensor ground wire. All of the sensor grounds can be connected to this wire to reduce then possibility of electrical noise.White/Black
Pin21VR2IN-/GROUNDFor early Sequencers™, this is one of several ground wire pins (18 through 23). All of the ground wires should be run to the same spot on the engine (to avoid ground loops). Make sure you have a good ground connection from the batteries negative terminal to the engine, and from the engine to the frame as well.

For later Sequencers™ (v1.04+ produced after August 2010), this wire is the ground for the VR2 circuit.

  • If you want a zero-crossing circuit (usually with a variable-reluctor, "VR", circuit), you connect this wire to the 'ground' side of the VR sensor (not to the engine block or any other ground).
  • If you have a Hall sensor (or optical, or other digital signal) DO NOT CONNECT this pin, leave it unconnected. This will put a 2.5V bias on then input, so the signal will be high if the input voltage is above 2.5 Volts, and ground if it is less than 2.5 Volts.
  • Black
    Pin22GROUNDThis is one of several ground wire pins (18 through 23). All of the ground wires should be run to the same spot on the engine (to avoid ground loops). Make sure you have a good ground connection from the batteries negative terminal to the engine, and from the engine to the frame as well. Black
    Pin23GROUNDThis is one of several ground wire pins (18 through 23). All of the ground wires should be run to the same spot on the engine (to avoid ground loops). Make sure you have a good ground connection from the batteries negative terminal to the engine, and from the engine to the frame as well.Black
    Pin24MAPThis pin is connected to the output from a MAP sensor that puts out a 0 to 5 Volt signal (roughly) proportional to absolute pressure. General Motors MAP sensors are suitable (Pin24 connects to pin B on the sensor, pin A is grounded, pin C gets 5 Volts from Vref (Pin28 on MS-II Sequencer™)). You can also use the original MPX4250 MAP sensor used with MegaSquirt, you connect the pion #24 to the sensor's Pin1, Pin2 is grounded, and 5 Volts (Vref) is connected to pin#3.Green/Red
    Pin25CLTMS-II Sequencer™ uses the coolant temperature to determine the warm-up enrichments. The sensor must be a negative temperature coefficient (meaning the resistance decreases as the temperature increases). Most automotive temperature sensor are this type, however the default sensors are General Motors sensors.Yellow
    Pin26IATMS-II Sequencer™ uses the intake air temperature (aka. manifold air temperature = MAT) to determine the air density for fuel calculations. The sensor must be a negative temperature coefficient (meaning the resistance decreases as the temperature increases). Most automotive temperature sensor are this type, however the default sensors are General Motors sensors.Orange
    Pin27TPSThis is a pin for the 'sense' connection on a throttle position sensor.

    To hook up your throttle position sensor (TPS), disconnect the TPS, and use a digital multi-meter. Switch it to measure resistance. The resistance between two of the connections will stay the same when the throttle is moved. Find those two - one will be the +5 Vref and the other a ground. The third is the sense wire to MegaSquirt. To figure out which wire is the +5 Vref and which is the ground, connect your meter to one of those two connections and the other to the TPS sense connection.

    If you read a high resistance which gets lower as you open the throttle, then disconnected wire is the one which goes to ground, the other one which had the continuous resistance goes to the +5 Vref from the MegaSquirt, and the remaining wire is the TPS sense wire.

    Blue
    Pin28VrefThis is a 5 volt supply for the throttle position sensor and the MAP sensor. DO NOT connect it to 12 Volts! The wire labeled "Vref" is the +5V voltage reference for the MAP sensor and the TPS sensor. This wire only connects to these components, so be very careful to not connect this directly to ground or (worse) +12V battery. Bad things will occur if you mis-wire this one - double check your work.Gray
    Pin29SPARE ADCCan be used for external baro MAP sensor.Orange/Green
    Pin30OPTOIN+Square wave ignition signal input positive connection for Input 1. Note that you can use only one of OPTIN+/- or VRIN+/-, because they connect to the same processor pin. For the second ignition input (Input 2), use VR2IN+ (Ampseal pin 4)Gray/Red
    Pin31OPTOIN-Square wave ignition signal input negative for Input 1. Note that you can use only one of OPTIN+/- or VRIN+/-, because they connect to the same processor pin. For the second ignition input (Input 2), use VR2IN+ (Ampseal pin 4)Gray/Black
    Pin32VRIN1+Variable reluctor A/C signal input for Input 1. Note that you can use only one of OPTIN+/- or VRIN+/-, because they connect to the same processor pin. For the second ignition input (Input 2), use VR2IN+ (Ampseal pin 4)Silver (coax center wire)
    Pin33VRIN-Variable reluctor A/C signal input (ground) for Input 1 & Input 2 (if used). Note that you can use only one of OPTIN+/- or VRIN+/-, because they connect to the same processor pin. For the second ignition input (Input 2), use VR2IN+ (Ampseal pin 4)

    For later Sequencers™ (v1.04+ produced after August 2010), this wire is the ground for the VR1 circuit.

  • If you want a zero-crossing circuit (usually with a variable-reluctor, "VR", circuit), you connect this wire to the 'ground' side of the VR sensor (not to the engine block or any other ground).
  • If you have a Hall sensor (or optical, or other digital signal) DO NOT CONNECT this pin, leave it unconnected. This will put a 2.5V bias on then input, so the signal will be high if the input voltage is above 2.5 Volts, and ground if it is less than 2.5 Volts.
  • Silver (coax shield)
    Pin34O2This is connected to the oxygen sensor output wire. This may be a 0 to 1 Volt signal directly from a narrow band sensor, or a 0 to 5 Volt signal from a wide band sensor controller.Pink
    Pin35TACH OUTPUTThis connection can be used to drive a standard tach (OEM or aftermarket). For details on how to hook it to your tach, see your tach installation manual or OEM service manual.Green/Yellow

    "RED" Ampseal:

    It is critically important to realize that IGNX, INJX, etc. refers to the Xth cylinder in the firing order. For example, on a small block Chevrolet with a firing order of 1-8-4-3-6-5-7-2, IGN4 in connected to cylinder #3 (the fourth cylinder in the firing order). Similarly, INJ6 connects to cylinder 5, and so on.

    PinNameFunctionHarness Wire Color(s)
    (main/stripe)
    DRAFT
    Pin 1INJ8This is the injector GROUND for the cylinder that is 8th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the injector ground for cylinder #2 (the front passenger's side cylinder). With a four cylinder and a firing order of 1-3-4-2, this injector driver ground is not used.not assigned yet
    Pin 2INJ7This is the injector GROUND for the cylinder that is 7th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the injector ground for cylinder #7 (the back driver's side cylinder). With a four cylinder and a firing order of 1-3-4-2, this injector driver ground is not used.not assigned yet
    Pin 3GNDGround wire. Ground to the engine block. On the grounds, you need to tie the high current grounds on the red connector (the one with all of the injector outputs) to the engine block. There is a break in the ground plane layer which separates the high current items (injector drivers, stepper chip, low-side drivers) from the digital and analog side (on the green end).not assigned yet
    Pin 4INJ6This is the injector GROUND for the cylinder that is 6th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the injector ground for cylinder #5. With a four cylinder and a firing order of 1-3-4-2, this injector driver ground is not used.not assigned yet
    Pin 5GNDGround wire. Ground to the engine block. On the grounds, you need to tie the high current grounds on the red connector (the one with all of the injector outputs) to the engine block. There is a break in the ground plane layer which separates the high current items (injector drivers, stepper chip, low-side drivers) from the digital and analog side (on the green end).not assigned yet
    Pin 6INJ5This is the injector GROUND for the cylinder that is 5th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the injector ground for cylinder #6. With a four cylinder and a firing order of 1-3-4-2, this injector driver ground is not used.not assigned yet
    Pin 7GNDGround wire. Ground to the engine block. On the grounds, you need to tie the high current grounds on the red connector (the one with all of the injector outputs) to the engine block. There is a break in the ground plane layer which separates the high current items (injector drivers, stepper chip, low-side drivers) from the digital and analog side (on the green end).not assigned yet
    Pin 8INJ4This is the injector GROUND for the cylinder that is 4th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the injector ground for cylinder #3. With a four cylinder and a firing order of 1-3-4-2, this injector driver ground is for cylinder #2.not assigned yet
    Pin 9GNDGround wire. Ground to the engine block. On the grounds, you need to tie the high current grounds on the red connector (the one with all of the injector outputs) to the engine block. There is a break in the ground plane layer which separates the high current items (injector drivers, stepper chip, low-side drivers) from the digital and analog side (on the green end).not assigned yet
    Pin 10INJ3This is the injector GROUND for the cylinder that is 3rd in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the injector ground for cylinder #4 (the rearmost cylinder). With a four cylinder and a firing order of 1-3-4-2, this injector driver ground is for cylinder #4.not assigned yet
    Pin 11INJ2This is the injector GROUND for the cylinder that is 2nd in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the injector ground for cylinder #8 (the rear passenger's side cylinder). With a four cylinder and a firing order of 1-3-4-2, this injector driver ground is for cylinder #3.not assigned yet
    Pin 12INJ1This is the injector GROUND for the cylinder that is 1st in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the injector ground for cylinder #1 (the front driver's side cylinder). With a four cylinder and a firing order of 1-3-4-2, this injector driver ground is for cylinder #1.not assigned yet
    Pin 13IGN8This is the ignition coil logic-level signal for the coil on the cylinder that is 8th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the coil signal for cylinder #2 (the front passenger's side cylinder). With a four cylinder and a firing order of 1-3-4-2, this coil driver signal is not used.not assigned yet
    Pin 14IGN5This is the ignition coil logic-level signal for the coil on the cylinder that is 5th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the coil signal for cylinder #6. With a four cylinder and a firing order of 1-3-4-2, this coil driver signal is not used.not assigned yet
    Pin 15IGN3This is the ignition coil logic-level signal for the coil on the cylinder that is 3rd in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the coil signal for cylinder #4. With a four cylinder and a firing order of 1-3-4-2, this coil driver signal is for cylinder #4.not assigned yet
    Pin 16IGN1This is the ignition coil logic-level signal for the coil on the cylinder that is 1st in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the coil signal for cylinder #1. With a four cylinder and a firing order of 1-3-4-2, this coil driver signal is for cylinder #1.not assigned yet
    Pin 17GPI-1This pin (as well as pin 30) has a 5V pull-up circuit, and so it should only be used as an input, unless the pull-up circuit is disabled by removing the 4.7K Ω pull-up resistor R86. You may also need to jumper the 10K Ω resistor R85 (which is in-line with the processor pin), depending on your intended use.not assigned yet
    Pin 18GNDGround wire. Ground to the engine block. On the grounds, you need to tie the high current grounds on the red connector (the one with all of the injector outputs) to the engine block. There is a break in the ground plane layer which separates the high current items (injector drivers, stepper chip, low-side drivers) from the digital and analog side (on the green end).not assigned yet
    Pin 19BOOTLOAD1This pin is grounded to enter bootloader mode, which allows you to update the embedded code in MS-II Sequencer™'s sequencing processor. You can connect this lead to a switch, with the other side of the switch connected to ground. When you close the switch and reboot MS-II Sequencer™ EFI controller, you will be in bootloader mode. (On beta units, this lead should be tried to Vref when not actively using the bootloader.)not assigned yet
    Pin 20R-PW1This is the output that is controlled when the user elects to use the 'PA0 - Knock Enable' spare output in the tuning software (spare port 6, MS-II pin PA0).not assigned yet
    Pin 21X2not assigned yet
    Pin 22X4not assigned yet
    Pin 23X5not assigned yet
    Pin 24IGN7This is the ignition coil logic-level signal for the coil on the cylinder that is 7th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the coil signal for cylinder #7. With a four cylinder and a firing order of 1-3-4-2, this coil driver signal is not used.not assigned yet
    Pin 25IGN6This is the ignition coil logic-level signal for the coil on the cylinder that is 6th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the coil signal for cylinder #5. With a four cylinder and a firing order of 1-3-4-2, this coil driver signal is not used.not assigned yet
    Pin 26IGN4This is the ignition coil logic-level signal for the coil on the cylinder that is 4th in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the coil signal for cylinder #3. With a four cylinder and a firing order of 1-3-4-2, this coil driver signal is for cylinder #2.not assigned yet
    Pin 27IGN2This is the ignition coil logic-level signal for the coil on the cylinder that is 2nd in the firing order. For example, with the small Chevrolet firing order of 1-8-4-3-6-5-7-2, this would be the coil signal for cylinder #8. With a four cylinder and a firing order of 1-3-4-2, this coil driver signal is for cylinder #3.not assigned yet
    Pin 28GNDGround wire. Ground to the engine block.not assigned yet
    Pin 29GNDGround wire. Ground to the engine block.not assigned yet
    Pin 30SEQ_PT3Will be used for spare port 7 in the future. This pin (as well as pin 17) has a 5V pull-up circuit, and so it should only be used as an input, unless the pull-up circuit is disabled by removing the 1K Ω resistor R96. You may also need to jumper the 10K Ω resistor R95 (which is in-line with the processor pin), depending on your intended use.not assigned yet
    Pin 31R-PW0This is the output that is controlled when the user elects to use the 'PM3 - Injection LED' spare output in the tuning software (spare port 1, MS-II pin PM3).not assigned yet
    Pin 32X1not assigned yet
    Pin 33X3not assigned yet
    Pin 34X6not assigned yet
    Pin 35X7not assigned yet

    Injector and Power Wiring

    Note that MS-II Sequencer™ and the injectors MUST be powered off the same relay (the 'main relay'). If the injectors are powered while MS-II Sequencer™ controller is not, the injectors might be grounded and flood the engine with fuel.

    Grounds

    Make sure the grounds are correct. When running the grounds on MS-II Sequencer™ EFI controller, it is important to remember that there are different "types" of grounds. These are:

    1. High power grounds (RED Ampseal pin 3, 5, 7, 9, 18, 28, 29): On the grounds, you need to tie the high current grounds on the red connector (the one with all of the injector outputs) to the engine block. There is a break in the ground plane layer which separates the high current items (injector drivers, stepper chip, low-side drivers) from the digital and analog side (which are also separated). All the grounds come together at one point, this is why there is no resistance when you measure it. Same for the return for the switcher PS.

      The ground path for the high current drivers will circulate thru the "RED" connector. The sensors will circulate thru a return path that is the "sensor ground" wire on the "GREEN" connector side. Connect all the sensor returns to this wire BUT DO NOT GROUND THE WIRE, it will follow the return path back to the analog ground plane. If you ground the sensor wire then you could cause a ground loop.

      As for the number of ground wires, more parallel wires are better than one fat one. It is important to run all the wires because it will reduce both the resistance and the overall inductance of the ground return path. Each wire has a resistance, and using three of them in parallel reduces the overall resistance. But it's not just that each wire forms a parallel resistance, it is also that each wire has a small inductance and many wires become lots of small inductances in parallel. We want minimal inductance with all of the switching loads going on.

      Inductances do not "like" fast-changing signals (like a pulse from a spark) and can cause very brief voltage offsets in the ground path. By having multiple wires it is the same as having multiple inductors in parallel, resulting in an overall lower inductance. At the point on the engine block where the grounds hook together, it is a good idea to run a separate wire from this junction back to the battery as well. This is redundant, however it often cleans up noise from sources like the starter motor. And, if it does help then you should take another look at your big positive and negative wire on the battery. Since we are talking battery - the point where you pick up the +12V to power the MS-II Sequencer™ controller is very important. This will go through a relay in order to turn on and off the MS-II Sequencer™ EFI controller, and the power source for the +12V on the relay needs to go back to the battery, or a path that leads direct to the battery without a long run of wiring. Just like for the grounds, run a separate wire from the relay direct back to the battery just to be sure.

    2. Sensor ground (GREEN Ampseal pin 20): the coolant sensor, intake air temperature sensor, throttle position sensor, and external MAP sensor needs to be grounded back to pin 20 on the AMPSEAL. This is the low-current sensor return path and it needs to be kept away from the high power ground. This wire hooks directly to the sensors only and not to the engine block - it is its own return path.
    3. VR return ground (GREEN Ampseal pin 33) - there is a separate VR(-) input on the AMPSEAL, this needs to be connected to the VR sensor(s). If you are using two VR sensors, return both back to this wire (these are low current and can be shared on the one wire return path) Do not ground the VR sensor anywhere else, return the ground back to the VR(-) terminal. On the MS-II Sequencer™ EFI controller, this return goes directly back to the VR input circuit's transistor/op amp and not to the ground plane, this keeps the high amplitude VR voltages (and resulting currents) isolated to the VR circuit.
    4. Serial return (GREEN Ampseal pin 19) - the serial cable on the MS-II Sequencer™ has a separate ground return path thru the AMPSEAL connector. This return goes direct to the RS-232 transceiver (and not thru the ground plane, keeping the noise off...).

    With the small size of MS-II Sequencer™ EFI controller, keeping the grounds straight is important. It is not hard, just keep things in logical groups - high power stuff goes to engine block, sensors on their own ground loop, and the VR sensor is also separate. The ignition coil current path is from the battery to the ignition coil to the MS-II Sequencer™ driver and back. The same goes on for the injector and general purpose outputs. Lots of juice flowing on this path, it needs to stay away from the sensors. It also needs a low resistance/inductance loop. The Vref is the reference voltage generated by MS-II Sequencer™ EFI controller, it passes thru the sensors and the return ground path comes back to the MS-II Sequencer™. Only one return path is required for the sensors because it is comparatively low current, and we all know that voltage drop across a wire is driven by Ohm's law (V=I*R).

    Ignition Wiring

    In general, MS-II Sequencer™ can be wired the same as MegaSquirt-II for ignition input (tach) signals. However, there are a few of things to note for those installs that are direct-driving ignition coils with MS-II Sequencer™ (i.e. not using an ignition driver module but the internal VB921 drivers in the MS-II Sequencer™):

    Manifold Absolute Pressure (MAP) Sensor Wiring

    This sensor is critical to how MS-II Sequencer™ functions. the MAP sensor tells MS-II Sequencer™ the intake vacuum (or boost) the engine has, and use this to scale the fuel injected. These generally have three electrical connections: 5 Volts, ground, and a signal. In addition to the electrical connections, the MAP sensor also has a vacuum connection the intake manifold - this must be downstream of the throttle(s), in the plenum area.

    A separate baro sensor (for full-time barometric pressure sensing, rather than just using the startup value) is connected the same way, but the signal wire is connected to AMP pin 29 via the orange wire with the green stripe. Vref and ground can be shared.

    For the popular GM MAP sensors (which come in 1, 2 and 3 bar versions) the wiring is:

    and has:

  • Ground on Pin A,
  • Sensor output on Pin B, and
  • +5 Vref on Pin C.
  • (Note that ABC are swapped from the previous diagram!)

    Coolant Temperature Sensor Wiring

    The temperature sensors that are default sensors for MS-II Sequencer™ controllers are General Motors two-pin sensors. You can use other temperature sensors by entering 3 resistance/temperature data points into a dialog in MegaTune (under 'Tools/Calibrate Thermistor Tables"). A lot of temperature sensors (aka. "senders") designed for gauge use have one end grounded to the threads for contact in the engine block. This is fine for gauge work, but for EFI you will notice that the majority of the sensors have two terminals (and insulated from the case/thread) such that a separate ground to the ECU can be implemented. This to eliminate the possibility of an erroneous ground path introducing errors in the readings.

    One of the pins is ground, and the other goes to MS-II Sequencer™. It doesn't matter which pin you use for which function. You can use other temperature sensors by inputting appropriate values into MegaTune (see: www.megamanual.com/megatune.htm#oh). If you have substituted a one pin connector, the body of the sensor is grounded to the engine, and the pin is connected to MS-II Sequencer™.

    Intake Air Temperature Sensor Wiring

    The temperature sensors that are default sensors for MS-II Sequencer™ controllers are General Motors two-pin sensors. You can use other temperature sensors by entering 3 resistance/temperature data points into a dialog in MegaTune (under 'Tools/Calibrate Thermistor Tables"). For two-pin sensors, one of the pins is ground, and the other goes to MS-II Sequencer™. It doesn't matter which pin you use for which function. You can use other temperature sensors by inputting appropriate values into MegaTune (see: www.megamanual.com/megatune.htm#oh). If you have substituted a one pin connector, the body of the sensor is grounded to the engine, and the pin is connected to MS-II Sequencer™.

    The IAT sensor must be placed to measure the temperature of the air entering the manifold. In a normally aspirated engine, this can be almost anywhere in the intake tract (air cleaner, throttle body, etc.) since air temperature does not change a lot. For a boosted application (blower of turbocharger), the intake air temperature should be measured in a boosted part of the tract (since compressing the air raises its temperature), and you should use an 'open element' IAT sensor: www.megamanual.com/v22manual/mwire.htm#clt

    Fuel Pump Wiring

    MegaSquirt controls the fuel pump operation. This is to shut the fuel pump down if the engine stalls, preventing the pump from running unnecessarily (or in the case of a crash).

    Exhaust Gas Oxygen Sensor Wiring

    An exhaust gas oxygen sensor (EGO) is optional but useful for tuning with MegaSquirt. You can use either a narrow-band sensor, or the more useful wide-band sensor (with a controller).

    Fast Idle Valve Wiring

    The fast idle valve is used to increase engine speed when the engine is cold, preventing it from stalling. MS-II Sequencer™ can use either a 'solenoid'-style ON/OFF valve, and a variable pulse width modulation valve. See: www.megamanual.com/ms2/IAC.htm#fidle

    Throttle Position Sensor Wiring

    To hook up your throttle position sensor (TPS), disconnect the TPS, and use a digital multi-meter. Switch it to measure resistance. The resistance between two of the connections will stay the same when the throttle is moved. Find those two - one will be the +5 Vref and the other a ground. The third is the sense wire to MegaSquirt. To figure out which wire is the +5 Vref and which is the ground, connect your meter to one of those two connections and the other to the TPS sense connection.

    If you read a high resistance which gets lower as you open the throttle, then disconnected wire is the one which goes to ground, the other one which had the continuous resistance goes to the +5 Vref from the MegaSquirt, and the remaining wire is the TPS sense wire.

    Accel and Warm-Up LED Wiring

    These circuits ground the LED to light them. You can use the Vref 5 volt supply on Pin 28 to power the LEDs, or you could use some other source. For example, you could use the battery supply voltage (nominally 12 Volts) as long as you increase the current limiting resistor value to 1K Ohms (to keep the current within limits).

    Spare Ports

    Ports A0 and M3 cannot be used as spare ports for the Sequencer™ controller because they are used as control lines by the ECU to signal the Router processor when synch has been lost and when a new tach cycle begins. These have been replaced by 2 new spare outputs (they can even be used as PWMs when code is so written). These pins are on the Router processor and using them is completely transparent to the user. You use them just as you did A0 and M3, but wire to pins 31 (old A0) and 20 (old M3) on the second (output) Ampseal. They can also both be turned on/off via a CAN message from the main processor to the Router.

    In addition, a third GPIO input from the Router, with 5 V pullup, was added on Ampseal pin 30 for possible future use. This could also be used as a PWM output controlled via a CAN message to the Router, but the pullup would have to be removed. The following table summarizes this:

    OutputsFunctionControlPull-up Components
    Router PT0
    (Ampseal R-PW0, pin 31)
    GPIO
    PWM
    ECU, CAN device
    CAN device
    none
    Router PT1
    (Ampseal R-PW1 pin 20)
    GPIO
    PWM
    ECU, CAN device
    CAN device
    none
    Router PT3, w pullup
    (Ampseal SEQ-PT3 pin 30)
    GP Input
    PWM
    CAN device
    CAN device
    R96 (1K Ω) pull-up to 5Vref,
    plus R95 (10K Ω) in-line to processor pin
    (remove R96 pull-up if used as an output)

    The is also a pull-up circuit and in-line resistor on GPI-1 (pin 17). This consists of 4.7K Ω resistor R86. There is also a 10K Ω resistor R85 on GPI-1 (which is in-line with the processor pin).

    Using the Relay Board with MS-II Sequencer™

    Check the MS-II Sequencer™ access board, which may be a better choice than the relay board for some installations.

    You can use MS-II Sequencer™ with a relay board, if you like. You will need to solder many of the leads from the suppled harness (extending them as necessary) to a female DB37 solder cup connector (like Digi-Key 2237F-ND, and a suitable hood (937GME-ND), if desired and if temperatures permit). The connecting cable should be wired like this:

    The above diagram has an error. Pin 32 should be the VR + lead, pin 33 should be the ground. These are reversed in the above diagram.

    Note:



    MegaSquirt®, MicroSquirt® and MS-II Sequencer™ controllers are experimental devices intended for educational purposes.
    MegaSquirt®, MicroSquirt® and MS-II Sequencer™ controllers are not for sale or use on pollution controlled vehicles. Check the laws that apply in your locality to determine if using a MegaSquirt®, MicroSquirt® or MS-II Sequencer™ controller is legal for your application.
    ©2009, 2010 Bruce Bowling and Al Grippo. All rights reserved. MegaSquirt® and MicroSquirt® are registered trademarks. This document is solely for the support of MegaSquirt® boards from Bowling and Grippo.