GMC C1500 - Answered Questions & Fixed Issues

I suggest taking it back to the shop that rebuilt it.

Why don't you just cut 2 wires where you know they're good, add 2 new wires, and run them to the back, and by-pass whatever the problem area is, and your done?

Hello Chris
Here is a diagram for you. hope it is large enough as we are not allowed much space here to post pictures.

Change ignition module in distributor and test coil

Might be caused by tranny filter being dirty

Put you a couple of more body grounds on it if that helps From the Block to the fender and from the frame to the body

You have so many problems but not much to work with. Let's try something to help you out. 1. Instrument panel is it Analog or Digital 2.For speedo and tach do you have a speedo cable attach to the cluster? If it's with speedo cable. Inside the transmission, there is a plastic gear could be worn. And the cable at the cluster's end could be stripped or not install properly. If it's with the digital cluster the speedo works with a buffer module near the glove compartment (It convert the analog signal to digital signal for a digital cluster. I could tell you more but need too many info. There is many instrument panel depends on the options. See options: links Hope it helps. Find out instrument panel pinout (or electrical diagram) for wires testing. 1. There is more ground than only one and there more + wires at cluster panel. I will have to check those circuit and finally find the problem.

I found window motor connector for your vehicle at rockauto.com, it was two wires, so that is up and down, correct? Sorry, I don't have wiring diagram for your vehicle year? The closest I could get was 1990 for gmc pickup. If the wire colors match up, it may work?

It may not be the alternator causing the vibration - it could be something else being driven by that belt. I would take off the belt and check the idler pulley first, then the rest to see if there is a misaligned pulley or one of them is very rough or loose when being manually turned.

this is probably a bad u-joint(s) crawl under the truck engine off and in park and on a flat spot, twist the drive shaft if it clunks at all or has some up down or left right slop the joints are shot and will need replacing. And yes the u-joints will cause a drive line vibration that seems like a transmission issue it goes away with speed as the shaft will spin fast enough the vibration will become only a hum.

Hi, P0122 code i think reads as "low input" on the fault text, if thats so, the fault is most likely with the wiring to/from the tps, low input codes would usually relate to a short on the wiring so check for any chaffing or corrosion on wires and multiplug connectors, ideally you need to check voltages at the tps connector.

You may have a leak vacuum or part. Check hoses and then fittings. A switch is changing or temp sensor maybe be an issue also. Check engine codes also

Chevy 2500HD No Start No Spark No Fuel Cranks OK Testing !!!

have flushed an change filter if no work,rebuild!!

check timing ?

Found these two fuses for hvac. Use a test light, check voltage on fuse circuit, key on. Yes, the ignition switch is involved. Check feed to ignition switch, both show to be red wires, hot all the time. The feed from ignition switch to hvac shows to be orange wire.

Yes the trans can wipe out the crank bearings or the spacer behind the crank(forget what its called) it can let the flexplate move and the bolts can hit.That may be what your hearing. Does it still have good oil pressure?

Of course.

Have you tried replacing the fuel pressure regulator in your EFI (carburator) Sorenson sells a kit that has all the gaskets, screens and regulator for around $30.

See if cleaning the throttle body helps - TUTORIAL HOW TO clean Vortec Throttle body 5 7L Chevy Gmc