I have an interesting one.

Symptom: No MIL No start at first, If you leave key on for aprox. 1 min the fuel pump relay kicks in and aprox 1 min after the MIL will start to come on dimly and then full on, vehicle will run fine will start right back up for about 5min after shutting off, then must start all over.

Have tried: Well aware of splice 115, have pulled apart entire harness across fire wall and redone all splices. Have power on pins 3, and 9 @ PCM, Replaced all relays in box. Batt voltage is good.

Thoughts: Possible ground issue with PCM or PCM itself.

Request: Wiring Diagram I have does not list grounds for PCM. Any thoughts and suggestions welcome. Only liability so gas and a match not an option!
Thanks in advance for any info.

 

at the computer plug, pin 3 should be the +12v supply, both pins 11 and 12 are grounds for the computer. First use a meter and check the voltage across the terminals of the battery and make a mental note of that voltage. Do all of this with your key off. Then check voltage from pin 3 to a good known ground anywhere (i.e. a good shiny bolt on the firewall). If that reads the same voltage as you got across your battery, the positive feed to the comp is good. Next use the meter and check voltage from pin three to pins 11 and 12 to check the computer grounds for full voltage. The rows of pins on the connector are numbered and are easy to find by counting. Hope this helps

 

Tyler's got some good info! Check continuity from pins 11/12 to the battery negative. The grounds go to a bracket that attaches the intake manifold to the alternator bracket (one of the wiring diagrams posted here say it's on the back of the engine, not so). Here's a pic:


If by chance that bracket is broken like mine was replace it or jump it out to test.

 

Actually that is not a ground it is a support bracket.


Yes there is really a ground strap that runs from the firewall to the engine block. See the large green arrow.


The wire you attached to the support bracket must of not gotten a strong ground so once you fixed the support bracket it supplied a good ground path. I believe that ground wire in your picture goes to the back of the engine as well. Or it might be the one that connects to the front of the engine along with the main ground coming off of the battery.

 

Hey thanks for all the info, grounds were all good new PCM and she lit right off!!! Now just time to recoop a little cash and start the mods.

 

Crazy- thanks for the info! I saw that ground strap to the block and firewall. I think the brackets are corroded where they mate up to the block and that bracket was the only remaining good connection until it broke. It and all of the other grounds are on my "replace due to previous owner" list.

 

had a similar issue everything would seem fine then when you tried to start it, it would just click like the starter was going out and all the dash lights dimmed like the battery was bad. turned out i just needed to clean my battery terminals....