Hi guys browsing this forum has been so informative and helpful but I am hitting a wall on a truck that I am working on.

It's a 2000 GM C3500hd,6.5 with dual tanks 2wd and a dump body with around 89,000 miles on it. The complaint was intermittent stalling but always restarted. The PMD was replaced by someone else a few years back and has a relocate kit and a large heat sink that it's mounted to. The glow plugs and the controller were replaced a few months ago.

I swapped the PMD with a new one that i got for my truck and it fired and ran for a few hours with no stalling. Then it died on the owner.

I went back and did the following to the truck:

replaced with a brand new PMD (so I can have mine back)

checked alternator voltage and battery connections. output is 14.2 and clean connections.

replaced oil pressure sensor with a new ac delco sensor

checked fuses and verified they were ok

swapped fuel relay with a new one

cleaned the grounds on the top of the engine and the ground straps

tested the lift pumps with direct power and they function

jumped out the pins in the fuel relay to check lift pumps as well

unplugged the optical sensor and it does the same stalling

checked the function of the fuel shut off solenoid

checked the main plug and for chafing at the firewall for the ecm

it had a po231 code for low fuel pressure

I wiggled the ignition switch wiring and the key switch itself


I have lights and directionals and no other symptom that would be an indicator that the computer is bad.

I found that the Lift pump starts then cuts out after the glow plug controller cycles but I didn't think those circuits were related. Also, the fuel balance modulator needs to be replaced, but i'm not sure if it's related or not.

I also checked in for chafing or corrosion behind the glove box at the ecm.


The fuel Modulator is going to be replaced so they have a working gauge. I'm thinking my next step would be to check the PMD extension harness, and then i'm wondering about the crank position sensor as well. Is there a good way to determine if the ecm is bad and is there a schematic showing the wires for the lift pump circuit off the ecm?

I know it's a lengthy post but i wanted it to be known what was done and if I'm on the right path

Thanks in advance!