2010 Peterbilt 387 ISX CM871 Lost ECM Power

[runningman777]

I traced the two wires that connect to the hot side of the battery isolator switch back to pins 3 and 4 of the ECM power connector. Pin 4 also jumps to the priming pump connector.

Both fuses to those wires were blown - one was a 25 and the other a 30.

The truck ran fine for about 1000 miles on a single 15A fuse.

I did not see any evidence of where those two wires had shorted to ground before reaching the ECM. I'm still going to check the sensor wiring to make sure I don't have anything going to ground anywhere.

As you mentioned, it may be the ECM that's failing. If vibration causes the ECM to short, there's something loose inside. I know there's a recall for later ECM's that were assembled with a screw that would short out the circuit board leading to loss of power. I know my ECM was replaced before I bought the truck so it's possible that it was one of those ECM's.

Any recommendations on obtaining a replacement ECM? I think I'd better find one soon and get the truck to Haggai so they can get it programmed properly for me.