ECU wiring
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2nd Gear
Joined: Oct 2014
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ECU wiring
Hi guys new guy here, have an 87 vet that I had computer fail in and I know that's rare and that something else usually takes the ecu out but I put in a new one with the old prom cuz guess its an act of god to find a replacement one for it, anyway the new computer worked it runs but I am skeptical that there is something still wrong cuz I can hook up my scan tool one time no prob then if I back out of the data stream and go to the diagnostic codes it says error check connections. if I turn off the key and wait a couple min and turn on it will connect again but for only the one section I look at first. leads me to believe that there is another problem that will take new computer if I don't find it. I have checked the pin points on the ecu plugs and im confused on two things, one on D15 and D16 witch are the injector outs I get power where it should be ground with key on? and same with the injectors at there plugs unless I unhook all the injectors on each side of motor then I get the one power and the ground but if I plug in just one of them or more I get power thru both sides of the injector plug??
Race Director
Joined: Apr 2002
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From: Anaheim CA
I have checked the pin points on the ecu plugs and im confused on two things, one on D15 and D16 witch are the injector outs I get power where it should be ground with key on? and same with the injectors at there plugs unless I unhook all the injectors on each side of motor then I get the one power and the ground but if I plug in just one of them or more I get power thru both sides of the injector plug??
All 8 injectors are connected in parallel. Because of the fairly low resistance of the injector coils (about 15 ohms each), you will see a voltage on pins D15 and D16 if even one injector is plugged in. When the injectors are not turned on (ground applied to the light green and light blue wire) both pins of the injector connector will measure 12 volts if at least one injector is plugged in. That's because there is no current flowing so there is no voltage drop.
This diagram shows the fuel injector wiring connections:
Thread Starter
2nd Gear
Joined: Oct 2014
Posts: 2
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Pins D15 and D16 are connected together inside the ECM. The ECM applies ground to those pins to make the injectors pulse. When that ground is not being applied those pins will measure the voltage supplied by the INJ1 and INJ2 fuses, 12 volts.
All 8 injectors are connected in parallel. Because of the fairly low resistance of the injector coils (about 15 ohms each), you will see a voltage on pins D15 and D16 if even one injector is plugged in. When the injectors are not turned on (ground applied to the light green and light blue wire) both pins of the injector connector will measure 12 volts if at least one injector is plugged in. That's because there is no current flowing so there is no voltage drop.
This diagram shows the fuel injector wiring connections:
All 8 injectors are connected in parallel. Because of the fairly low resistance of the injector coils (about 15 ohms each), you will see a voltage on pins D15 and D16 if even one injector is plugged in. When the injectors are not turned on (ground applied to the light green and light blue wire) both pins of the injector connector will measure 12 volts if at least one injector is plugged in. That's because there is no current flowing so there is no voltage drop.
This diagram shows the fuel injector wiring connections:
