Hey everyone,
I’m looking for some help with my 2011 LML Duramax 6.6L. I bought the truck not running — the CP4 pump had grenaded, and someone had already been tinkering with it.
After confirming the CP4 failure myself, I replaced the following components:
I was told the ECM might be bad, so I sent it to G7 Computers for repair. The truck is deleted, and they said they could repair the ECM without affecting the tune. They sent it back saying it was “repaired,” but didn’t give any real details about the issue.
Now that everything’s back together, the truck will start briefly with shot of ether but then dies. If I try to build fuel pressure manually, it might hit for a second and die again. Sometimes it just cranks but never fully starts.
Using my Snap-on Apollo 9 scanner, I’m seeing the following:
When I unplug the fuel rail pressure sensor on the driver-side rail, the reading doesn’t change — it stays locked at 31,000 PSI. The sensor has three wires:
The truck also isn’t communicating with the Glow Plug Control Module (GPCM). I’m not sure if that’s related to the no-start issue, but I wanted to mention it just in case it matters.
At this point, the rail pressure reading is frozen at 31,000 PSI no matter what I do, and the truck won’t start but hits every now and then
P0641, P0532, P0193, P0192, P2294, U0106, P0340, C0561, U1511, B0775, B0780, B0785, B0790, B2725, P0677, P0675
Any advice or direction on what to check next would be greatly appreciated — especially if anyone’s dealt with a CP4 failure followed by multiple electrical and fuel pressure codes like this.
Thanks in advance!
I’m looking for some help with my 2011 LML Duramax 6.6L. I bought the truck not running — the CP4 pump had grenaded, and someone had already been tinkering with it.
After confirming the CP4 failure myself, I replaced the following components:
- New CP4 pump
- New fuel rails
- New injectors (programmed correctly after installation)
- New fuel filter housing and fuel filter
- FASS lift pump (already installed on the truck)
- New water separator and fuel pump filters
I was told the ECM might be bad, so I sent it to G7 Computers for repair. The truck is deleted, and they said they could repair the ECM without affecting the tune. They sent it back saying it was “repaired,” but didn’t give any real details about the issue.
Now that everything’s back together, the truck will start briefly with shot of ether but then dies. If I try to build fuel pressure manually, it might hit for a second and die again. Sometimes it just cranks but never fully starts.
Using my Snap-on Apollo 9 scanner, I’m seeing the following:
- Actual rail pressure: locked at 31,000 PSI (never changes, even while cranking) or unplugged
- Desired rail pressure: only goes up to about 1,200 PSI while cranking
When I unplug the fuel rail pressure sensor on the driver-side rail, the reading doesn’t change — it stays locked at 31,000 PSI. The sensor has three wires:
- Red: 0 volts
- Yellow: 5 volts
- Brownish-gray: 0 volts
The truck also isn’t communicating with the Glow Plug Control Module (GPCM). I’m not sure if that’s related to the no-start issue, but I wanted to mention it just in case it matters.
At this point, the rail pressure reading is frozen at 31,000 PSI no matter what I do, and the truck won’t start but hits every now and then
Current Codes:
P0641, P0532, P0193, P0192, P2294, U0106, P0340, C0561, U1511, B0775, B0780, B0785, B0790, B2725, P0677, P0675
Any advice or direction on what to check next would be greatly appreciated — especially if anyone’s dealt with a CP4 failure followed by multiple electrical and fuel pressure codes like this.
Thanks in advance!
