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2001 Chevrolet 3500 8.1 crank no start


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Hello everyone,

 

I am looking for some help with diagnosing the problem with the truck I recently purchased. Below is the back story on the truck and what I have done to it so far.

 

I purchased this 2001 Chevrolet 3500 Reg. Cab Dually LS 4WD with the 8.1L and Allison trans for $1300. The previous owner tried to jump start the truck with a welding machine, which from what he told me, burned up the ECM and TCM. The truck sat for about two years before I bought it and during that time they robbed several parts off of it to put on another Chevrolet they owned. I have replaced both the ECM and TCM and had them programmed for that truck. I installed a new ignition switch (one of the parts they robbed) and new ignition lock cylinder. I also put a new Interstate battery in it. I had to replace all the relays under the hood, and I checked all the fuses both under the hood and under the dash. The fuel tank was drained and all the lines cleaned, new fuel filter was installed. I put in new spark plugs and new wires, changed the oil and filters on both the engine and trans. The instrument cluster did not work so I purchased a reman unit and had the mileage programmed to what the mileage was suppose to be which was 222K miles. Once all of that was done, I checked fuel pressure at the fuel rail and was getting just under 60psi.

 

I attempted the passlock relearn according to what I have read on this site. One thing I would like to mention at this point is that after the 10 minute period with the key in the run position, the security lamp never went off. I continued the process but after I completed the sequence, the truck would still not start.

 

I have heard that it can be a finicky procedure so I disconnected the battery for 30 minutes and tried the relearn two more times. It still did not start.

 

At this point, I hooked up my Tech 2 and tried to read the BCM. The Tech 2 will not communicate with the BCM. I pulled up the ECM and made sure the VIN was correct from the reprogramming and everything looked good. I decided that maybe the BCM had been damaged as well so I purchased a new BCM. I have not had it programmed to the truck yet, but I installed it and attempted the passlock relearn again, still no luck.

 

I hooked the Tech 2 back up and it will not communicate with the new BCM either.

 

It will communicate with all the other modules, just not the BCM.

 

Can anyone offer some advice on where to go from here? I am itching to get this truck on the road and it is killing me running into this brick wall. Any help or advice would be greatly appreciated!

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I will go through and check all the wiring hopefully this evening. It was recommended to start with the comm wire from the BCM to the spice pack. Would I be testing that for continuity, or should it have a certain voltage?

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Continuity, as the line will vary between ground and some voltage in order to communicate.

 

If you have an oscilloscope, or something like that, you could also check that you are getting communication at the bcm.  I don't know offhand what the expected voltage range should be.

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I checked the continuity and the wire is good with very little resistance. I also checked the grounds and they are good. I am planning this evening to check the 12v power wire to the BCM.

 

one thing I am wondering, my tech 2 will communicate with the airbag module, but the passenger airbag was blown when I got the truck. Is there any kind of safety interlock that would affect the signal from the BCM to let the truck start if it thought for instance it was in a collision? Idk, just thinking out loud.

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