DieselDavy
08-02-2013, 06:48
Hi guys,
My 97 Tahoe is in "intensive care" and needs some help.
I took it to a regional diesel shop (Craigville Diesel Service) (where dealers send their problem trucks) to get some pump work done. I had to trailer it there as it wouldn't start and run by the time I took it there. (They started it right up of course and got it in the shop....)
Codes are:
P0251 Pump Cam reference Pulse Error
P0370 High Resolution Circuit Fault
After these codes appeared, it slowly deteriorated to the point where it is now.
Now, I'm an electronic design engineer and I understand the technology involved here, but I'm not sure I know how to use the proper terminology as it pertains to the workings of the GM diesels, (ie. Base Timing, TDC, injection closure, etc) So in order to keep me from posting misleading info I've copied the text below from the tech (Jerod) that is working on it now. (He said this one is the most difficult 6.5 he's worked on)
Jerod asks for any ideas that any of us may have. I've passed along John (Kennedy)'s advice to concentrate on the wiring harness especially the 15 pin connector at the rear of the engine. Jerod has already spent considerable time buzzing out the harness but I too believe it is wiring related and he needs to spend some more time there.
Anyway, here is what Jerod's done so far:
Started by installing an encoder sensor (cam sensor). Cleared codes and started truck. Truck still didn't have a signal from cam sensor. It was running in base timing and creating cam misfires per our scan tool. Installed new GM crank sensor. Same result after starting truck. Pulled injection pump and mounted on test stand and found fuel solenoid response time was too long. Pulled head and rotor apart and checked keyway. Installed new armature and set gap. Installed back on test stand and calibrated pump. Installed old encoder sensor and calibration went well. Installed on truck and truck acted same as before. Tested wiring from encoder sensor to PCM. The resistance was OK. Checked for 5V reference and computer was supplying ground. Everything checked OK. Repaired ground Y-connection in factory harness. Kennedy diesel supplied alternative PCM. Truck acted same as before. Installed complete injection pump/PMD (NEW). Truck acted the same. Double checked and repaired ground wires on back of motor and cleaned all connections for grounds on engine and batteries. Installed new encoder connector pigtail on engine harness. Truck acted the same.
Truck cranks 10-12 sec and starts. Truck then runs at full timing and still does not show actual timing reference or injection closure.
Jerod has also checked for air in the fuel system.
Thanks in advance for any advice!
My 97 Tahoe is in "intensive care" and needs some help.
I took it to a regional diesel shop (Craigville Diesel Service) (where dealers send their problem trucks) to get some pump work done. I had to trailer it there as it wouldn't start and run by the time I took it there. (They started it right up of course and got it in the shop....)
Codes are:
P0251 Pump Cam reference Pulse Error
P0370 High Resolution Circuit Fault
After these codes appeared, it slowly deteriorated to the point where it is now.
Now, I'm an electronic design engineer and I understand the technology involved here, but I'm not sure I know how to use the proper terminology as it pertains to the workings of the GM diesels, (ie. Base Timing, TDC, injection closure, etc) So in order to keep me from posting misleading info I've copied the text below from the tech (Jerod) that is working on it now. (He said this one is the most difficult 6.5 he's worked on)
Jerod asks for any ideas that any of us may have. I've passed along John (Kennedy)'s advice to concentrate on the wiring harness especially the 15 pin connector at the rear of the engine. Jerod has already spent considerable time buzzing out the harness but I too believe it is wiring related and he needs to spend some more time there.
Anyway, here is what Jerod's done so far:
Started by installing an encoder sensor (cam sensor). Cleared codes and started truck. Truck still didn't have a signal from cam sensor. It was running in base timing and creating cam misfires per our scan tool. Installed new GM crank sensor. Same result after starting truck. Pulled injection pump and mounted on test stand and found fuel solenoid response time was too long. Pulled head and rotor apart and checked keyway. Installed new armature and set gap. Installed back on test stand and calibrated pump. Installed old encoder sensor and calibration went well. Installed on truck and truck acted same as before. Tested wiring from encoder sensor to PCM. The resistance was OK. Checked for 5V reference and computer was supplying ground. Everything checked OK. Repaired ground Y-connection in factory harness. Kennedy diesel supplied alternative PCM. Truck acted same as before. Installed complete injection pump/PMD (NEW). Truck acted the same. Double checked and repaired ground wires on back of motor and cleaned all connections for grounds on engine and batteries. Installed new encoder connector pigtail on engine harness. Truck acted the same.
Truck cranks 10-12 sec and starts. Truck then runs at full timing and still does not show actual timing reference or injection closure.
Jerod has also checked for air in the fuel system.
Thanks in advance for any advice!