DTC 29, 34, 39, 46, 57 & 62 - Need Help ASAP

[gmenor]

I just pulled these codes after experiencing low boost. I also have a loud knocking sound coming from the right front (passenger side) valve cover. I cleaned all the grounds that I can find with all these codes. Bad part is I'm up in Fredericksburg, VA and I live in Fayetteville, NC.

These are what the DTC Codes are

29 Glow Plug Relay Circuit Fault
34 Injector Timing Stepper (ITS) Motor Circuit Fault
39 TCC Brake Switch Stuck "Off"
46 MIL Service Engine Soon Circuit Fault
57 PCM 5 Volt Shorted
62 Turbo Boost Sensor Circuit Low

[Kennedy]

Based on the 5v shorted, and all the voltage related items, looks like possibly a shorted wire or component somewhere. The hard part is finding out where...

[gmenor]

JK,
I just started tugging at wires and cleared the codes it hasn't come back. I'm going to drive back tonight - 4 hours to Fayetteville. Thanks

[BUZZ]

May recent right front knock was a failing vacuum pump. I have Turbo master rod so vac. pump has been removed and a shorter belt installed.

[gmenor]

Well got the beast back into town with no problems. Tomorrow I plan to check out the vacumn system. My boost was down to 3.5 @ 70 mph and EGT was up by 100 degrees. The turbo is definitely making a racket under load (similar to an exhaust leak). As Buzz stated could this be an early sign that the vacumn pump is going south? I know I haven't checked the vacumn system yet but, can it effect the turbo as indicated? I can move the waste gate actuator arm while the engine is running even though there is pressure on it.

[tom.mcinerney]

Routine checks for 'process elimination':
Engine cold, OFF-
remove serp belt, rotate accessories , for smooth & quiet
Remove rubber 90*angle tube from turbo out to intake ...rotate turbo shaft with fingers, check axial/radial play , see all vanes, no rubbing on hsg.
Engine On-
check vac at pump, then at turbo connection. The vac pumps have been described as quite noisy in death throes; turbo blades make noise when ingested in cylinders. Not sure if easier to R&R turbo to check exhaust driven blades....
A piece of tubing held to ear and spot on block can assist in localizing noise generator.
good luck

[GMC Hauler]

Like Buzz, I also had a right front noise which turned out to be the vacuum pump. Use a mechanics stethoscope (cheap at any auto parts chain store) and listen to the vacuum pod on the pump. To be absolutely sure, put the stethoscope on an injector line. The noise from a bad vacuum pump is more rapid than injector noise at idle. The hard part is that my vacuum pump was intermittent. You could also take the belt off and run the engine like that for a few seconds.

The vacuum system can affect the the turbo, like you stated. I could move my actuator rod on mine with a vacuum applied. The force is not that great.

If you decide to get rid of the vacuum pump, I have a shorter belt with only 1000 miles on it in the classified section.

[gmenor]

I did the vacumn test and the vacumn pump was bad. I replaced the Autozone (2 years old) vacumn pump with an OEM from the dealership. What a difference in boost level. I spiked 10 lbs and boost is up about 2 lbs. Even though the OEM pump had a sticker "Made in Bulgaria" on it, it performs better than the Autozone. Turbo has a different whistle to it under load and I am paying close attention to that. I think I tracked the short down to under the airconditioning tubing behind the turbo. I ended up taping it up and had no codes set. With all the codes it set I initially thought it was a ground problem. The noise I heard in the right front went away after I started pulling on the wiring harness. I assumed it had had something to do with cylinders firing out of order. Thanks all.