94 6.5 Diesel pulling multiple codes

Bought this truck from my work about 2 months ago. It was a trade in. Got it for $750. Ots a 94 K2500 long bed with a 5 speed. Awesome truck! Love this thing and dont ever wanna get rid of it. When I first bought it, it was pulling a code 29 for faulty glowplug relay and code 31 for wastegate solenoid. The wastegate solenoid was bad so I replaced it and it fixed that issue. Then it popped up with a code 36 but still had the 29. Wasnt totally sure what to think. It's now showing code 29, 36, 49, 57, and 62. The pmd is relocated to front bumper and has aftermarket 9 blade engine fan as well as straight pipe exhaust. No other mods yet. The check engine light sometimes comes on and then goes away. It does this intermittently almost everytime I drive the truck. Usually after its warmed up itll only come on at high speeds. Sometimes it wont come on and off at all. When I comes on, itll stay on until I decelerate then go off till I accelerate to a certain speed again. Last night, the truck bucked about 3 times. Never done that before. It did miss a few times at idle a few months ago but has been absolutely perfect since. And in the mornings even when it's not cold and I go to start it up, itll smoke white/blue/grey for about 10-20 seconds and then be fine. Done that since I bought it. If I hit the accelerator itll go away quicker. Any ideas? Truck has 195k miles.

Welcome to TDP

The odd array of codes may not be all that tough to fix.
Battery voltage and grounding are critical.

The 1994 feeds the battery voltage off the RH battery via a cable from the battery +++ to a stud in the junction box by the RH cowl area.
Starter feeds off the RH battery as well.... Alternator feeds the LH battery

Check battery voltage with the engine running at the following places.

Alternator stud

Left side battery ++

Right side battery++

Power stud in the junction box on the cowl

If you see anomalies...check between each +++ and a solid engine ground with your volt meter. (You can isolate and ferret out bad battery ground cables this way.

All readings need to be the same at around 14 volts with the engine running.

The alternator feeds the LH battery and then the power crosses to the RH side in the heavy cable over the radiator support.

Be sure all cables are good...even though the side terminals may look good the cables can and do corrode in the fine inner strands.

Even the grounds corrode at the block in the inner strands.

Make sure you have the same voltage all the way.

Near the RH rear of the intake manifold are a small bundle of wires that ground to the engine.

Be sure all of these wires are in good shape and that the ground is clean and secure.

These wire come from the main harness.


Make sure that the ground wire from the PMD harness is attached to the Injection pump.

Many times when folks move the PMD they move the ground...../ GROUND must stay on the IP


Get all these things checked and then clear all the codes from the ECM and then run the thing and see what pops up.

If you see a much lower voltage at any one battery it means there is a cable issue...voltage at the power stud in the junction box must read near 14 V too with engine running.

The voltage is important and issues with voltage will drive the ECM nuts (You too)

Also be sure that there is a ground from the ENGINE TO THE BODY AND THE FRAME (CRITICAL)

Time and sloppy mechanics can see these left off or having corroded beyond usefulness.



Good luck