Ok, I need some help. Let me start at the beginning. I was driving my 07 GXP (Trifecta budget tuned) when I got a CEL then the DIC showed Check ESC, Traction Control Off. I was almost to work so I shut the car off at work, thinking I would look into it after work. Well after about an hour my horn started going off (alarm). I thought I had hit the panic button in my pocket so I just hit it again and it stopped. Then 30 minutes later, someone said your radio is on in your car. I said that’s not possible, I have my keys in my pocket. I went out and sure enough the radio was blaring. When I opened the door, the chime was going off as if my keys were in the ignition. I put my keys in then turned them off and everything looked normal. I tried to start the car and nothing. The guages would swing but then drop out when I turned the key and I would get all of the same errors as before but then I started getting air bag and security.
I thought maybe the battery was run down from the radio so I tried to jump it. I had no luck for about the first 15 minutes of trying then all of a sudden it started. I decided to drive it home while I could. The trip home was very interesting. The dash looked like a Christmas tree with lights coming on and off. The gauges would swing wildly and the air would come on and off all by itself.
Once I got it home and turned it off it wouldn’t start again. I was getting tons of codes U102 was one of them. I did a lot of research and went to the BCM connections first. They all looked good, front and back. Then I checked the ECM connectors and found corrosion on the left connector and one of the pins had completely oxidize away.
I thought I had found the problem so I bought an ECM from Mallet. After installing the ECM the check ESC and traction control warnings went away as did some of the random relay actions. After following the key learn process, I tried to start it and it wouldn’t start and I got a CEL again and an air bag light.
Next I checked the ground wire on the drivers side of the engine. It had corrosion, so I cleaned it and cleared the CEL’s and tried again. Still no start but now no other CEL’s. I was down to two CEL’s, U101 which I found out was because the ECM I bought was originally for an Auto car and it is looking for the TCM and the P0615.
At this point I got the schematic and my powerprobe out. What I found is that the PCM is not sending a ground signal to Relay 34, the Crank relay. I was able to start the car by pulling the crank relay and energizing the starter relay.
Jut to ensure it was the ground I was loosing, I put a meter on the hot side of the crank relay coil and pushed in on the clutch and it got power. So I am certain the ECM is not sending the ground. See the drawing.
I highlighted the ground signal wire as yellow.
What would cause the ECM not to send the ground to start?