2010 Peterbilt 387 ISX CM871 Lost ECM Power

[runningman777]

Monday my 2010 Peterbilt 387 with an ISX-15 CM871 suddenly died with no speedometer or tach. Engine crank with no start, and the priming pump would not run. I found no BAT + to the 4 pin ECM connector. To get off the side of the road - very windy and snowing - I ran +12V thru a 15A fuse from the mega fuses to the ECM and moved to a rest area. The next morning I had a brief shut down with a red warning on the display but by time I got to the side of the road it was back running. Didn't get but a brief glimpse of the dash as I was trying to steer to the side of the road in snow. Delivered the load and made it home OK for a total of about 1,000 miles since the first shut down.

I'm assuming there's a fusible link somewhere that either opened or got corroded.

I don't have Insite but do have a diagnostic tablet to check codes.

I had 4 codes, none were active:

2374 2X Exhaust Gas Bank 1 Pressure Sensor 1 Circuit - Voltage Below Normal or Shorted to Low Source.

2448 5X Coolant Level - Data Valid But Below Normal Operating Range - Least Severe Level

197 18X Coolant Level - Data Valid But Below Normal Operating Range - Moderately Severe Level

2554 3X Exhaust Gas Bank 1 Pressure Sensor 1 Circuit - Data Erratic, Intermittent, or Incorrect

The two for low coolant was from actually running a little low.
The other two are both for exhaust gas pressure. Truck is de-mandated.

I checked the wiring to the exhaust pressure sensor and the pigtail has been replaced and the splices look good.

I'm going to look at as much of the sensor wiring that I can expose looking for possible shorts.

I would think that the ECM would current limit a shorted sensor wire so as not to allow it to blow a fuse or fusible link. Those codes may not be related to the power loss but that's just a possible lead for me to follow.

I do not have accurate schematics for my truck. The ones I've been able to find are close but they don't actually show the path thru fusible links. The only fuse for the ECM is switched ignition and it's only 5 amps.

This truck has a battery isolator switch and there's two smaller wires there - could they be BAT+ going to the ECM? I don't know if those wires are stock or somebody's jury rig...

My ESN is 79365436, VIN 1XP7D49X1AD793392

Any assistance and accurate schematics would be greatly appreciated!

[Rawze]

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.

[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.

[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.

[Rawze]

(11-15-2025 )runningman777 Wrote:  ...
Any recommendations on obtaining a replacement ECM?
...

ONLY BUY OEM.! ...

- HAVE THEM PRE-FLASH IT FULLY BEFORE TAKING IT AWAY FROM STEALERS$IT!.

- INSTALL IT AS IS AND RUN TRUCK + bang on it a bit to test it to ensure there is nothing wrong with it.

== OTHERWISE, ITS YOUR ARSSE,. AND YOUR OUT ANOTHER $2,000 - $3,000 + FOR SEVERAL MONTHS IF IT DOES NOT WORK OUT OF THE BOX FOR ANY REASON!.

[runningman777]

I just found a recall for my ECM. It was a Cummins Re-Con part number P3684275-RX and the serial number starts with a "B" so it's covered under NHTSA Recall No. 19E-074.

The recall says I need to: Contact the nearest Cummins Distributor or authorized Warranty Dealer to arrange to have this campaign performed. Would MHC in Macon be able to do this or PeterBilt in Jackson?

Do I need to have the truck re-mandated before taking it to a stealership, or just wait until after they are done with it?


  RCONL-19E074-8734.pdf (Size: 94.73 KB / Downloads: 1)