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Ok, I’m going to run the pinpoint tests I can with my limited equipment. I’m going to start with c8 and c9 because they are easier. Then I need to extend the leads on my dmm and run c7. Also, I just noticed this morning that the truck has no interior lights. It has dash and steering wheel lights but no dome, reading, or entry lights. It’s probably not related, but I need to check the fuses for that.
Pin 18 in the PCM plug is shorted to ground. It goes to pin 5 on the dtr plug which is tr2. Pin 5 has 12.2V with the key on and unplugged from the trs sensor. So, looking at the schematic 18 is shorted to ground before the trs plug, how then is the pcm not in flames as referenced to by hayapower in post 40 above. Someone please explain this to me.
Also, what would account for the shift test changing? Do you think more than 1 wire is shorting intermeintly? Or is the pcm burnt inside now due to the grounded pin 18?
This is why I undo the battery when not working on it, and keep the lane behind it clear so I can push it out of the garage if it catches fire. I also keep a large extinguisher at hand.
Ok. So in post 43 I tested the dtr plug. I Tested with the key on engine off. Pin 5 which is tr2 was 12.2V, so it fails because it should be 0 V.
Pin out test C8 tests for shorts to ground or power in the pcm harness. I checked with the dts plug off and the pcm plug off. Battery hooked up, key off engine off. All pins were above 10k ohms except pin 18 which was 0.00ohms, between the pin and battery ground. So it fails this test also.
That means the LB-BK wire from pin 18 on the pcm to pin 5 on the dts plug is grounded when the key is off and engine is off, but has 12.2 V when the key is turned to on in park.
I think this means the LB-BK wire is shorted to ground, and when the key is turned to run it powers up to 12.2v somehow blowing fuse 14. It should not be grounded, but it also should not be 12.2 V at key on.
It must also be shorted to the LB-PK wire that powers pin 9, and that is how it blows fuse 14. It’s also how it does not fry the pcm. This explains why 14 does not blow with the trs unplugged. Someone reign me in! My brain is flowing on the screen, and I don’t know if my logic stands up.
Whatever the exact wires are that are shorted, I think I am looking at removing and repairing, or replacing the external trans harness. And maybe the pcm. I don’t know how it could be ok. I’m looking forward to others evaluations. Thanks
Merry Christmas everyone. I’m thankful for all the help. I’m done now until after Christmas, but I’ll get back on it right after. I’ll keep you posted.
Problem solved. The wiring harness was pinched on the passenger side top. I removed the wheel well cover and it was obvious. I had enough room after unplugging the harness to pull it out and repair it. Everything functions correctly now. I put 30 miles on it and the transmission is working great. Special thanks goes to hayapower. He supplied the schematics that allowed me to diagnose and find the problem. Thank you for your assistance as well hanky. Hope everyone has a great new year.
12-20-2018, 10:55 AM
