95 GMC K2500HD, maiden run, have codes and questions

[GM Guy]

Hey all,

Had a relatively successful first run out with the new to me 95 K2500HD with 431,000 miles.

I did have a few issues though,

on a hard pull, it would pull awesome for a while and then de-fuel, CEL on, and limited boost (I would call it 75 percent power, still plenty functional and had live boost, but not 100 percent power)

Due to it being a maiden voyage, I never found myself using the cruise at all.

Engine codes pulled post trip:
Code 71, which according to our own site's reference library, is cruise related (Set/Coast switch fault) The blinker/ Multi-function switch does feel a little on the cheap side, PO likely got it from carquest. definitely not original. think its a parts quality issue? I think this one is not a huge deal right now.


Code 78. reference library says Wastegate solenoid fault. does this mean it detected a fault within the sensor that replacement will cure, or is it a wiring issue?

Of course the code 12 self check code too.



Also, I did do the frame and rear intake grounds, but got lazy and did not do the cab ground under the heater hoses. Still need to do the battery terminals and the bolt mod, but when i put the new batteries in (was in a hurry) they looked clean.

Is code 71 possibly PMD related? I need to get one of my new ebay black Stanadynes mounted to one of Leroy's kits and run that, the current setup is laughable, homebrew at its worst.

I will also verify the wastegate moves freely and is not sticking. might be sticking when the ECM commands it to open maybe?


any input appreciated, Thanks!

 

[ak diesel driver]

Possibly sticking shut waste gate and over boost causing it to defuel. I would verify waste gate moves freely

 

[GM Guy]

good thought AK, i did notice it was doing it often early in the trip, and was doing it with less frequency later on, maybe it was stiff?

I did pull back the loom on the wiring going to the solenoid, and 431K miles worth of air rattling the loom around did some work! :O there is a few spots where it actually rubbed through the insulation, but I cant see a single place where they touched, I will wrap them anyways to make sure.

Any thoughts on the cruise? I wonder if its the clutch switch that senses when the pedal is up that could be the issue.

 

[ak diesel driver]

IIRC cruise won't engage with codes present. but also check brake switch etc.

 

[WarWagon]

Weak vac pump?

 

[GM Guy]

Weak vac pump?

I will hook up the guage to check for sure, but when I had the front of the motor apart, I could roll it over by hand and get it to suck up hard and hold vac. looks to be pretty new too.

 

[Big T]

Replace the solenoid. They're prone to freezing up from moisture. They're also cheap. If that doesn't correct it, then look at more expensive potential problems. You'd know if the vac pump is bad as they growl and complain.

 

[GM Guy]

OK, pump is pulling 22.5 inches at idle at the turbo connector, all tubing looks good. I put a new WG solenoid on and will carry the old one for a spare.

Also put a new pair of coolant temp sensors on, guage read high, and when I went to pop the plug off to see if there was any corrosion, the plug just broke off the sensor. No noticeable corrosion though. Figured the one in the crossover could not be far behind, so both are new Delco from the local GM dealer.

Hopefully all is well and behaves, headed to California next! :O

Probably better adjust up the rear brakes a little, parking brake has to travel pretty far and this pickup does not brake as well as the 93.

 

[Big T]

OK, pump is pulling 22.5 inches at idle at the turbo connector, all tubing looks good. I put a new WG solenoid on and will carry the old one for a spare.

Also put a new pair of coolant temp sensors on, guage read high, and when I went to pop the plug off to see if there was any corrosion, the plug just broke off the sensor. No noticeable corrosion though. Figured the one in the crossover could not be far behind, so both are new Delco from the local GM dealer.

Hopefully all is well and behaves, headed to California next! :O

Probably better adjust up the rear brakes a little, parking brake has to travel pretty far and this pickup does not brake as well as the 93.

Where in California?

I'm an Orange County native.

 

[GM Guy]

Big T, destination was Rio Vista, south of Sacramento.

Well, she made it! nothing like 19,xxx lbs going down, and 20,160 coming back, only a few tons over factory max GCWR.

1450 miles one way, stopped back up in Idaho on the way back to see Grandma. Should have kept driving, but that is a different story for a different area of the forum. truck rolled over 435K somewhere in Wyoming on the way back.

Once again, I love 5 speeds, and IMO you have to buy vehicles based on "vibes" I got a great vibe off this one, and it did not disappoint.

Post trip analysis: need a fan clutch. bad. auxillary cooling system B got a workout (cab heater on floor, fan on high, windows down) and the poor mans jake brake (a/c) got the cab cooled back down and tried to keep the coolant temp a little more consistent (try to reduce shock cooling) on the downhill run.

Got a stiff tailwind across Nevada on the way back, nothing like 1/4 throttle at 70 mph in the big hole.

 

[GM Guy]

also need to address the braking, I think some of the issue might be the power steering pump. Fluid looks decent, but when she is warm, it does not like steering around parking lots at idle, and braking is not fantastic. I think its a carquest special pump, definitely not GM.

Injectors need replaced at some point, and at the same time I need to get my water drain back on the FFM, PO deleted it.

 

[Husker6.5]

Glad it ran out fine for you. Kinda reminds me when I got the Money Maker. Flew down to Houston to pick it up. Left Houston at 4pm and pulled into the hotel in Wichita, KS at midnight. Gas gauge didn't work, read E all the time. Didn't know how much fuel the PO had left in it for me, a hunch told me to pull off in Denton to fuel it, put 33 gallons in!

Next morning pulled into an AutoZone in Newton, KS to get a temp sensor for the temperature gauge. Swapped it out in the parking lot and headed out. About two minutes later the needle started climbing rapidly and stopped just short of the red zone and stayed there! Talk about a moment of panic! Pulled over and checked the upper radiator hose. It was hot, but not unbearably so to touch, so I continued on the four hours to Lincoln. Next day went to the dealership and got a GM sender and put it in. Needle came up to 195 and held there. Learned my lesson about Chinese aftermarket sensors on that one.