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V3 MicroSquirt® - QuickStart Guide

Ampseal Connector Pin-Out for Your MicroSquirt® Controller

PinName
click for help
FunctionHarness Wire Color(s)
(main/stripe)
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 MicroSquirt® 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. This goes to one of the two VR sensor wires, or to a Hall sensor's signal; wire. Note that you must connect pin #21 appropriately to match your sensor.Brown/White
Pin5Spare Input 2This is a second spare ADC(ADC7). It is used for alternate MAF pin or knock sensing.TBD
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 idle air controller (IAC).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
Pin9INJECTOR 1This pin connects to the injectors. You connect half the injectors on one bank (INJECTOR 1) and half on the other (INJECTOR 2).Green
Pin10INJECTOR 2This pin connects to the injectors. You connect half the injectors on one bank (INJECTOR 1) and half on the other (INJECTOR 2).Blue
Pin11IGNITION OUTPUT #2Second logic level ignition output signal.White/Red
Pin12IGNITION OUTPUT #1Logic level ignition output signal #1.White
Pin13SERIAL Rx
(pre-wired)
This pin is used to receive data from the laptop computer serial port.Red (pre-wired to jack)
Pin14SERIAL Tx
(pre-wired)
This pin is used to transmit data to the laptop computer serial port.Orange (pre-wired to jack)
Pin15BOOTLOADERThis pin is grounded to enter bootloader mode, which allows you to update the embedded code in MicroSquirt.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. It can also be used as a spare port.Yellow/Black
Pin17Warm-Up LEDThis is the supply for an 'warm-up enrichment LED'. You connect the cathode (short lead) of and LED (light emitting diode) to this wire. It can also be used as a spare port.Yellow/White
Pin182ND SENSOR GROUNDPin 18 is a second sensor ground (in addition to pin 20) for those who require it. Pin 18 may not be populated on your harness, but this pin can be added later if needed.Black
Pin19SERIAL GROUND
(pre-wired)
Serial 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 the possibility of electrical noise.White/Black
Pin21VR2IN-This is the ground pin for the second variable reluctor input (typically for a VR or Hall camshaft sensor). For use with a variable reluctor sensor (that has an AC signal) connect this wire to the second VR sensor wire. For use with a Hall sensor, leave this wire 'floating' by snipping it off and sealing it.Black
Pin22GROUNDThis is one of several ground wire pins. The ground wires from pins 22 and 23 should be run to the same spot on the engine (to avoid ground loops).Black
Pin23GROUNDThis is one of several ground wire pins. The ground wires from pins 22 and 23 should be run to the same spot on the engine (to avoid ground loops).Black
Pin24MAPThis pin is connected to the signal from a MAP sensor that puts out a 0 to 5 Volt signal (roughly) proportional to absolute pressure.Green/Red
Pin25CLTThis is for the coolant temperature sensor (The other wire from the sensor, if it has one, goes to the sensor return ground (pin 20). The default sensors are General Motors sensors.Yellow
Pin26IATThis is for the intake air temperature sensor (The other wire from the sensor, if it has one, goes to the sensor return ground (pin 20). The default sensors are General Motors sensors.Orange
Pin27TPSThis is a pin for the 0 to 5 Volt signal from a throttle position sensor.Blue
Pin28VrefThe wire labeled "Vref" is the +5V voltage reference for the MAP sensor (and/or MAF 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, the +12V supply). Gray
Pin29Spare Input 1Can 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). If you are triggering directly off the coil, see this note. 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). If you are triggering directly off the coil, see this note. 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)TBD
Pin33VRIN1-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)TBD
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).Green/Yellow


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MegaSquirt® and MicroSquirt® controllers are experimental devices intended for educational purposes.
MegaSquirt® and MicroSquirt® controllers are not for sale or use on pollution controlled vehicles. Check the laws that apply in your locality to determine if using a V3 MicroSquirt® or MicroSquirt® controller is legal for your application.
©2011 Bruce Bowling and Al Grippo and Lance Gardiner. All rights reserved. V3 MicroSquirt® and MicroSquirt® are registered trademarks. This document is solely for the support of V3 MicroSquirt® boards from Bowling and Grippo.