I have this same question in another post, but I thought I post it individually. The test below is being done because I am trouble shooting the fact the my IAT sensor reads 140 Degrees Farenheit at start-up, (90 Degress outside) and 332 Degrees Farenheit when disconnected, (should read -30+ degrees Farenheit). This is causing my ECM to dump more fuel than necessary.

Did a little troubleshooting this weekend and came up with the following results.

I began to test all my ground wires to see if there is any voltage on them. I found one.

There are 3 ground wires attached to the retaining bolt on the ignition coil. 2 are black and the other is tan with a white line. I tested them individually and found that both black wires are fine.

When I tested the tan wire, I found that there was voltage on the line, it constantly read a negative (-) number. I traced it back to the ECM and disconnected the harness connector and proceeded to re-test the tan wire. It was now fine.

This means that this wire is not shorted out, but when it is connected to the ECM it is. It gives me the same negative number with ignition on or off. I guess there is a short inside the pcm.

I then tested the same wire on a (2) 1994 Lt1's and it read as it should, just like the other ground wires.

I then tested it on a 1996 Lt1, this one has two wires like it, and they also tested out fine. No voltage.

Is it safe to assume that my ECM is toast?

Thanks

 

Yes, congrats you're one of the 1 in 1 million cases that turn out to have a fried ECM while everyone else just blames it on them. But its possible your problem goes beyond your ECM too. good luck

 

"But its possible your problem goes beyond your ECM too."

Please explain.

Thanks