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94 Chevy K2500 6.5 Multiple Codes Present

That makes sense. The connector on my glowplug relay only as 3 prongs as well as the relay. My 95 has 4 prongs and my friends 93 has 4. The connector on mine seems a little bit loose too. One of the fusible links coming out of it has wire showing right before the fuse part. No telling how old it is or anything. Just thought it maybe had the wrong relay or something on it. The GP light usually comes on for 8 seconds or so then goes off. Will thanks for the info! I was gonna go with the Bosch plugs but I'm probably gonna go with the ACDelco now. Thanks for the info! I will try and look at the wiring going to the glowplug relay and see if I can figure out what's going on and fix it.
 
1993 is a self contained GP controller.
1994+ is ECM controlled aka a DUMB relay.

IRC The connectors should be slightly different so you don't mix up a 1993 and newer.
 
Well, how many prongs is a 93 supposed to have? And what exactly do you mean by a dumb relay?
 
Iirc the 93 should have 4 pins.

Dumb means not as much input control like on newer ones that use the ecm also to control.

Imo the older simple systems are far better. If it isn’t getting signal to turn on and it should because it’s cold outside and engine is cold - either bad connection or the 2 wire sensor is bad. Nothing else.

The advantage of the smart one is you can have the ecm programmer add in longer glow times if you want. But I dont live in a freezer like a lot of folks do. Even still, I would just add a solenoid from Leroy and a dash button.

I prefer simple systems and do anything “special” by hand instead of the confuser doing stuff. Mama says, Mama says, electronics is the devil.

Count the wires in the harness going to it.
 
Oh okay that makes sense. So not trying to sound dumb here but where is the two wire sensor that may not be bad?
 
Okay. Well I'm going to replace my glowplugs this weekend d going to replace the relay and go from there. Also, is it supposed to idld high at every cold start? I had another 94 that did. Thought maybe the IAT sensor was bad even though I replaced it. Was throwing a code 48 so I replaced the sensor. Havent checked since but I'm still not getting a high idle in the mornings with a cold start.
 
Again but no so relevant to the problem: the connector is different on 1994+. As you appear to own several years it's important to understand they are different. 1993 is 4 pins per the one I am looking at off my 1993.

Does your GP relay have 3 pins? How is the GP lamp acting? You are doing the work so I can only guess at how you decided the GP relay is bad. Keep that in mind with the following suggestion.

Check codes before $throwing parts$ at things. Clear codes and make sure they don't come back. If they do the repair was not successful and now you have to hope the new part was a fing good part. (Yes start over and new part doesn't get a free pass.) Yes, we are the quality control with the low bidder and "Can your slaves do it cheaper still?" garbage in a pretty box crap we get for parts today. One more time with feeling: "New Parts Don't Mean Good Parts!" (Go ahead and ask me about 30 min life before a reman Power Steering pump grenades and reman PIA starters that spin 3 of 4 attempts.)

With the electrical problems you have going on I suggest you consider getting a scanner that can read your computer aka ECM.

Let me bluntly do the math for you:
Scanner Software from Leroy Diesel $160.00
Cable $59.95
Used laptop $150.00
Diesel compression tester ($60-100)
Total ~$400.

And scanner values show you you have an intermittent open on a wire that takes an in stock crimp connector to fix... (Compression tester can give you good or very bad news.)



Throw parts at instead:
PMD $166.99*
PMD Cable $50.00
GP relay
Glow plugs
Glow plug extractor
Temp sensors
ECM

Doesn't fix it - you sell the truck at a loss with lots of maybe new good parts...

* PMD's are the only exception to throw a part at it due to the known and common intermittent failures they have. You have a known working spare PMD on a heatsink in the glove box right?

You have a MT... Drop a DB2 on it.
$1200 for a DB2 injection pump with warranty.
Injection lines.
1993 GP controller...
...
 
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Thanks for the info! My GP relay has 3 pins and the light only comes on for a out 6 seconds and sometimes 8. But it only comes on once. I'm ordering a spare pmd on payday (Friday). I have been looking at getting a scan tool and adapter thatd be able to read ECM data for this truck and for my 95 6.5. I apologize for not being super knowledgable on diesel stuff. I know way more about gas engines.
 
Diesels... Same primitive "Stupid Computer" as gas engines. Some differences with different trons devices used, but, same PIA electrical problems.


I would cycle the ignition switch a few times waiting 30 seconds between "off" and "on". Do you hear the GP relay "click" without the lamp coming on? (The ECM takes 30 seconds to reset after power off or it does weird things. Notable the STS and SES lamp test becomes random instead of both on.)

The scan software will give you a GP "on" indicator and commands to cycle the GP's. This can help pin the problem down.
 
So when I put a test light on the glowplug controller, there is power to the positive side but none to the ground. No power to the fusible links either. Is that something within the fusible links or something within the glowplug controller itself that is bad? Not getting power to glowplugs either. Is it possible that my controller just isnt grounded properly? Is it supposed to be grounded? I have two fusible links on the ground part of it.
 
One is ground, one positive, and ECM ground to "turn on".
1994GP.jpg
 
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