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Hard hot start causes

I too went to the T-6 and it made a lot of difference in the cold engine RPMs. Even with the engine heater plugged in, oil still stays cold setting in the bottom of the pan.
 
Time for an update, so lately my hard hot start has been rearing it's ugly head again. It's never not started but a couple of times I was wondering. Then today when I went to leave my job to go home it wouldn't start cold. Finally resorted to a little ether after I waited for the glow plugs to cycle. Got it home and checked codes and I had 4 of them the check engine light had actually come on last night but I've been getting a boost code so I mostly ignore the light and it will go out after awhile. So the codes I have are boost (no surprise), APP (not to surprising either get it occasionally when in subzero weather), but then I also had a U1000 which said something about loss of communication, and also a glow plug circuit code. So I guess I'm going to clear the codes and see what comes back
 
ak diesel driver said:
Cleared codes and this is what came back. Maybe @THEFERMANATOR can tell me how to check which module is not communicating with my tech 2View attachment 56319
Click to expand...
If any module on the bus drops offline, doesn't power up on time, or even if you put the wrong info in when hooking up the tech 2, you can get this. Is your abs and all that working?
 
Yes ABS is working but I did have a weird braking event a few weeks ago. Other thing I noticed this morning was that my clock time was off. Batteries were getting low from cranking but it did start without jumping.
 
the loss of comm is all the time now, clear it and it's right back. Friend of mine helped me check it with my tech2 . All the modules appear to be working but he didn't think they were comm with the pcm. Wondering if the body module not comm with the PCM could be part of my starting issues since it has the passlock in it
 
ak diesel driver said:
the loss of comm is all the time now, clear it and it's right back. Friend of mine helped me check it with my tech2 . All the modules appear to be working but he didn't think they were comm with the pcm. Wondering if the body module not comm with the PCM could be part of my starting issues since it has the passlock in it
Click to expand...
There is no body control module. Gmt-400's have the hall effect sensor at the lock cylinder, theft module, and then it sends a signal to the ECM to start. If there was a vats issue, it would start and shut off after 2 seconds, not a complete no start normally.
 
Ok, I pulled up the 99 service manual, and U1000 is not a valid code for your truck according to the GM manual. What are you entering when you connect to the vehicle? I'm wondering if you're entering it in so the tech 2 thinks it's a gmt800 instead of a gmt400.
 
I follow all the prompts year, truck, engine, k model, etc. My understanding is the passlock and the Evo and something else which I can't remember all are in the same module.
 
PCM ground getting hinky mayby?
I have DTC comms issues with my 99 as well. Schematic research shows there's a couple of wires that may be at issue with the Purple Wire seemingly the suspect. That one carries signal from more than a couple of components, one being pass lock if memory serves (I shelved the issue for later a long ways back). I'm in CA right now so, if you like, I'll scan the pages when i get back home. PO disconnected a few things under the dash (no light, seatbelt, door buzzers and I'm guessing the pass-lock too though its been deleted from the tune).
 
Anything other than U1000? There is NO listing AT ALL in the 98-00 C/K service manuals for that code.
 
Try connecting to it as a 98 and see what happens. I connect to gmt800's using the same C and K as I do gmt400's, so it may be looking for a non existent BCM.
 
PCM ground is on the back of the engine right? Is there more than one, maybe somewhere else? I'll try hooking it up as a 98 later today
 
Voltage and grounds. Low voltage to any computer screws them up. Digitally voltage must be over say 2.5v to be called a "1". So a low voltage condition a chip may only bring the voltage up to 2.1v for a "1" and the next chip thinks it's a "0".

What does the ECM see for voltage? Ignition switch failure is famous for brown outs and weird codes etc on some rides. Air bag lights, no AC, ghost codes, and next ign cycle everything is fine.
 
So I haven't had any time to deal with this but I had a close no start and popped another code. Hooked up the tech2 and it was another glow plugs circuit code. Went to clear it and got a message of couldn't communicate. So I'll need to deal with this communication issue sooner rather than later. Not sure if I can get to it this week or not.
 
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