2G No Check Engine Light

[2gTurBoD]

Its for a 95 gst 6 bolt swap.

OK i have searched all known dsm forums. And it wont let me post anywhere else so i have to put it here. I am not getting power to my ECU. Pin 80 the back up power source is not seeing any voltage at all. 82 the ignition pin is seeing source voltage. Pins 12,25, and 38 are also not seeing and voltage. I have 2 working ecu's; I have tested them in other cars.

I checked the MPI relay harness and there is a pin on that see's 12v when the switch is on and when the switch turns on it goes to low voltage, which i believe is what it is suppose to do.

I changed the fuses multiple times, but still cant find out why i have no power to at least pin 80. So basically where does pin 80 get its power from? I no its a battery back-up but does this run through a fuse somewhere?

I arrived at this problem when i finished my 6 bolt swap, and i wasnt getting any spark. My coil, cas, and transistor are fine. Any help is appreciated.

 

[TALONTRAX]

The keep alive memory or full-time battery power to the ECU is not fused (pin 12 on a 2G). Pin 71 is power to the ECU from the ignition switch, pin 38 is MPI relay output. There should be 12v. always at pin 12 & 12v at pin 71 with the key on. You can temporarily run a wire from the battery to pin 12 & see if it works. If it does, just make up a wire from the fuse box in the car that has 12v with the key off & run it to pin 12 . . .

 

[2gTurBoD]

The keep alive memory or full-time battery power to the ECU is not fused (pin 12 on a 2G). Pin 71 is power to the ECU from the ignition switch, pin 38 is MPI relay output. There should be 12v. always at pin 12 & 12v at pin 71 with the key on. You can temporarily run a wire from the battery to pin 12 & see if it works. If it does, just make up a wire from the fuse box in the car that has 12v with the key off & run it to pin 12 . . .

I ran the wire to pin 12 and now that showing around 12v, but still no go. Would 25 also need power or no?

 

[luv2rallye]

For 2g ECU: When key is on the ECU should pull pin 38 low which activates the MFI relay which provides +12V to pins 12 & 25. For it to do all this however you must have +12V on pin 80 (battery backup) which comes from the engine fusebox 10A "Room Lamp" fuse (2nd from left, bottom row).

 

[2gTurBoD]

For 2g ECU: When key is on the ECU should pull pin 38 low which activates the MFI relay which provides +12V to pins 12 & 25. For it to do all this however you must have +12V on pin 80 (battery backup) which comes from the engine fusebox 10A "Room Lamp" fuse (2nd from left, bottom row).

So really 80 should get the power from the wire I ran from the battery?

Also that is one fuse I completely over looked because I assumed it only involved the lights, thanks.

Also I know I don't have many post here, but between you, steve, and a guy who cataloged and pictured everything about his engine build. I have basically found the answer to any problem I have run into.

Keep up the good work here seriously.

 

[2gTurBoD]

Well I changed the fuse because it was blown and got power back to pin 80 like its suppose to. Still working on pin 38. I'm going to check the harness and see if I'm getting power to the relay. Does anyone know were I can get the MPI pin out?

 

[luv2rallye]

Thanx for the kudos. Steve and I do this freely out of our own time.
Here's the 95 MPI relay pinout/testing: http://www.dsmtuners.com/forums/problem-diagnosis/263224-mfi-mpi-relay.html.

 

[2gTurBoD]

Thanx for the kudos. Steve and I do this freely out of our own time.
Here's the 95 MPI relay pinout/testing: http://www.dsmtuners.com/forums/problem-diagnosis/263224-mfi-mpi-relay.html.

Ok i got power back to pin 80 it was the fuse. But the MPI pin and 12/25 aren't getting power still. I checked power at the harness and 2 pins are getting 12v when the power is off and 2 others are getting 12v when the switch is in the on/run position. I checked the fuse with my voltmeter and that was fine. And I'm not sure what else to check right now.

 

[luv2rallye]

You don't say which harness and pins/wires you're getting +12V at (ECU or MPI relay?).

On the MPI relay the 2 red/black wires (pins 4 & 8) should always have +12V. With the relay plugged in, the red and black/red wires (pins 2 & 3) should have +12V only when the relay is activated. The blue/green (pin 6 which goes to ECU pin 38), may be floating high (+12V) when relay is off but should be pulled down to 0V by the ECU to activate the relay. If this is pulled down to 0V and you have +12V on the red/blacks, you should then have +12V on the red and black/red or your relay is bad.

If all this is ok but you still don't have +12V on ECU pins 12 and 25, then you have a broken wire between ECU pin 12, 25 and MPI relay pin 3 (black/red).

 

[2gTurBoD]

You don't say which harness and pins/wires you're getting +12V at (ECU or MPI relay?).

On the MPI relay the 2 red/black wires (pins 4 & 8) should always have +12V. With the relay plugged in, the red and black/red wires (pins 2 & 3) should have +12V only when the relay is activated. The blue/green (pin 6 which goes to ECU pin 38), may be floating high (+12V) when relay is off but should be pulled down to 0V by the ECU to activate the relay. If this is pulled down to 0V and you have +12V on the red/blacks, you should then have +12V on the red and black/red or your relay is bad.

If all this is ok but you still don't have +12V on ECU pins 12 and 25, then you have a broken wire between ECU pin 12, 25 and MPI relay pin 3 (black/red).

Ok that interior fuse I replaced was the problem. I now have power to everything including the MPI pin on the ECU harness. But still no CEL, which leads to believe a busted ECU, and I'm trying to find someone to help me test them.

I've opened them both up and they look and smell fine. Both are from a 95 one is EPROM with DSMLink chip in it and the other one is a non EPROM.

Thank you for your help to get me this far.

 

[2gTurBoD]

Sorry to revive this thread, but i am still in the same situation. Good fuses, Good ecu and power is getting to the pins at the correct time, but the ecu will still not boot. I dont no whats left to check. It cant be the ignition switch or anything becauce i was told if that was the problem none of the on items would work. So i am really at a loss here anything else i might have overlooked?

 

[2gTurBoD]

Ok I have 95 GST with a 6 bolt swap. I just got done installing the engine and when I turn the key, I get no check engine light.

Now I've asked this question awhile ago and searched seems like every thread around on it. I just recenly got a break from school and work to finish it up. Now first I was wondering if I could get a picture of the actually check engine light on and was wondering if I can get some more things to check. I've checked the fuses all completely inside the engine bay and inside the car. I also have 3 working ECUs. And I've checked the power going into the ECU.

Also I'm not completely sure if the MPI relay isn't causing the problem. I have two of them, and when I switch them and turn the key, I get a click sound out of them. I am not sure if it's suppose to do this or not.

Like I said I've had this problem for about a year. Also are there any engine pieces that would affect this problem. Any help would be appreciated. The timing is also dead on I forgot to add in.

 

[black_gst]

the light for the CEL went out replace the little bulb

 

[2gTurBoD]

No it didnt because i replaced the bulb with a working a light and no go.

 

[black_gst]

Check pin 36 which is the output for your check engine light and check for continuity between that wire and the light socket in the cluster

Here's a ECU pinout.
http://www.dsmlink.com/images/forums/2GECUPinout.pdf