2010 Peterbilt 387 ISX CM871 Lost ECM Power

[runningman777]

(11-15-2025 )Rawze Wrote:  A. Fuel shutoff solenoids are notorious for killing engine randomly, or when it gets hot. - Removing the guts of the fuel shutoff solenoid and re-installing it would remove this from the causes... however, you described electric lift pump not working.. which points more towards ecm to me...

B. CM871 ecm itself is notoriously famous for getting intermittent and dying just like you describe. Get engine running and smack it with something almost hard enough to dent its casing.. if it cuts out, ecm is going bad.


C. Older Petes have a few issues for wiring and dying. Here is one of the more common known spots...
info: https://rawze.com/forums/showthread.php?...05#pid3505

could be either one.. but if i had to guess, your post implies a dying ecm more-so than actual wiring issues.

That thread very likely is my answer. According to the schematic I have for the HARNESS- ENGINE, CUM ISX PB387 P92-6083, the 12/24 VDC BAT (+), ECM comes from P2 CHASSIS LOAD CENTER, on pin 12 and 16. If that's one of the plugs on the driver's side firewall, I can't read the labels due to someone's paint job. I believe the open is going to be at a common point before those two 12V+ sources since they were both connected to each other but had no power on them.

Pin 12 feeds pin 4 of the ECM power plug P4 and pin 16 feeds pin 2 of P52 for the priming pump. Both wires are labeled 12/24 VDC BAT (+), ECM and this is what I lost. I verified the connection between pin 4 of the ECM plug and pin 2 of the priming pump plug and then spliced into the wire for the priming plug to inject +12V to get it running.

First place I'm going to look (after my morning coffee that is) is those two small wires going to the battery isolator switch. Maybe there's a fuse holder full of Yankee Cancer causing juice - you know what that stuff does to vehicles...

I forwarded that thread to a friend who has been battling intermittent issues with the automatic shifter on his KW. IDK if he is a member of your forum, but I'm sure he will be after reading that thread.

Thank you for your quick reply - I'll be sure to post back anything that I find so future readers will have more information to help them in similar circumstances. Unfortunately most people who post issues on forums never come back to let us know what they found and what fixed (or caused) the issue.