90 Wire Disaster! Please Help!

[@TDC]

Hey guys. I was in the middle of installing Link v3 Full in my 90 1g and I believe I came across the reason it is not working connecting correctly. 2 of my ECU harnesses are mixed up like crazy. My car was working perfectly fine. I tried to hook up my Eprom with Link and I cant get a response from the ECU. I created a drawing showing how the wires are right now along with some pictures of the actual wiring. I would really appreciate if another 1990 DSM owner could post some pictures of there ECU wiring harnesses.

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As you can see that Pin #2 has no wire in it at all. Pin #2 is Diagnostics/Data Transfer Select. I ran a wire from Pin #2 on the ecu to Pin 10 on the diagnostics connector hoping this would solve my Link connecting problem but still I cannot connect. This is how it looked when I first took a look this morning. You can see the light shining through where the wire should be.

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Here are pics of the actual wiring.

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This is the wire from harness C-59 Pin #107 that has a different wire from what the pin out says should be there.

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[@TDC]

If there are no codes, there should be small fluctuations in voltage (repetitive short pulses). If it remains constant (pegged) -- and I find it hard to believe considering you've said the car runs fine otherwise -- that is indicative of an ECU problem.

ECU Code Checking

The car does run fine. Also my ECU just came back from ECMTuning after getting socketed and the v3 chip installed. It was confirmed that the ECU was working fine. Caps were even replaced. This happened no less than a week ago?? CEL does not stay on after ignition is turned on and no noise is coming from the ECU at all?? Hopefully today I'm gonna try connecting with a windows computer and if it connects I'll know it was my Mac if not then all that seems to be left is send the cable back to be tested!

 

[19Eclipse90]

Let's confirm that the ECU is sending the proper signal to the diagnostic port to get it out of the way. Check for the repetitive short pulses using a buzzer or voltmeter like you're checking for codes.

 

[@TDC]

Let's confirm that the ECU is sending the proper signal to the diagnostic port to get it out of the way. Check for the repetitive short pulses using a buzzer or voltmeter like you're checking for codes.

Sounds great sir! I will definitely give that a try today. I will post back with results. I will most likely post back with results after the 49er game today. Sorry guys watch my 9er's

Let's confirm that the ECU is sending the proper signal to the diagnostic port to get it out of the way. Check for the repetitive short pulses using a buzzer or voltmeter like you're checking for codes.

I tried using a buzzer to check the diagnostic connector to assure the ECU was working fine I put the positive wire from the buzzer to pin #1 of the diagnostic connector and the ground on pin #12 of the diagnostic connector. Then I switched the ignition to the ON position and got nothing. I tried the buzzer on a fuse and grounded it. It then buzzed so I know the buzzers working fine. I then tried to measure the voltage at pin#1 and I only got a reading of 0.03v sometimes 0.04v when i'd move the probes around. Is this ECU related or just something with my car???

 

[dsm-junkie]

Email ECMTuning they should be able to help.

 

[@TDC]

Email ECMTuning they should be able to help.

I actually emailed them already and they said theres nothing I more I can do My only options are to find someone local that has link for a 1g dsm and use there parts or just ship everything back to them to double check that everything is working correctly. I am gonna try and use a windows computer tonight and if that doesn't work then IDK what I'm gonna do next.

 

[19Eclipse90]

For S&Gs, try reading the output at the ECU rather than the diagnostic port. Take your voltmeter and put the negative on pin #12 on the diagnostic port and the positive to ECU pin #1.

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If it reads the same as it has been, something is up with the ECU. If not, there's a connection problem between the ECU and the diagnostic port. I'd expect the latter as that isn't going to affect how the car runs. On the other side of that coin, it's hard to argue with a continuity test, too.

 

[@TDC]

For S&Gs, try reading the output at the ECU rather than the diagnostic port. Take your voltmeter and put the negative on pin #12 on the diagnostic port and the positive to ECU pin #1.

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If it reads the same as it has been, something is up with the ECU. If not, there's a connection problem between the ECU and the diagnostic port. I'd expect the latter as that isn't going to affect how the car runs. On the other side of that coin, it's hard to argue with a continuity test, too.

Just tried it with the multimeter! Put positive probe in pin #1 of the ECU and the negative of pin #12 of the diagnostic connector. and got the same reading as before. It would just stick at 0.04. I also measured for continuity between pin #12 of the diagnostic connector and pin #1 of the ECu and got a reading so the connection between the 2 pins is fine. So does this mean its the ECU? Could it be another pin of the ECU that can affect pin #1???

 

[19Eclipse90]

That's all I've got. If it is steady at 0.3-0.4v and doesn't pulse back to zero at all (should actually be pulsing between 0-12v), I would conclude there's something fishy going on in the ECU.

Similar threads, for reference: http://www.dsmtuners.com/forums/tuning-engine-management/184764-1g-diagnostic-port-mmcd-issue.html and http://www.dsmtuners.com/forums/newbie-forum/259160-diagnosis-pin-ecu.html.

 

[@TDC]

That's all I've got. If it is steady at 0.3-0.4v and doesn't pulse back to zero at all (should actually be pulsing between 0-12v), I would conclude there's something fishy going on in the ECU.

Similar threads, for reference: http://www.dsmtuners.com/forums/tuning-engine-management/184764-1g-diagnostic-port-mmcd-issue.html and http://www.dsmtuners.com/forums/newbie-forum/259160-diagnosis-pin-ecu.html.

Alrighty! Thank you for all of your help! I really appreciate you taking the time to help me out. I have already emailed ECMTuning about sending it back for testing. I hope it is just a minor mishap with the ECU but thanks again!!

 

[@TDC]

Really weird! I tested for continuity between pin #1 of the diagnostic connector and ground...I got a couple readings so it was grounded right? So I made a direct line from diagnostic connector pin #1 to ecu pin #1 and still got continuity to ground on the pin?? How is that possible?? Lol I also got the same voltage readings after making the direct line.

 

[@TDC]

I am so happy to say that this problem has been solved!!! It was the ECMTuning cable that wouldnt let me connect to link!!!