lcorrell

First, let me appologize for not coming back an updating my topic! I hate when I find topics that could contain the exact info I need only to find that the topic was never updated with the resolution. The key to me figure out my issue was that the position of the shift lever changed the behaviour of my problem. I don't remember how I figured that out, but it turned out to be very important info. I started tracing the wiring diagrams in my repair manual. I focused on the shift position switch that's mounted on the side of the transmission. I individually checked each wire against the repair manual for ground, power, etc. I found that the ground wire to the switch did not have ground. Traced that to a broken ground connection on the rear of the passenger side cylinder head. Apparently the ecm, bcm, or something along those lines used this same grounding point and due to the lack of ground they were backfeeding through other circuits. Fixed that ground point and everything was fine! So, I never really did find out about the BCM programming issue since I didn't have to replace mine. I think it's rediculous that I'd be at the mercy of GM to program a part - that makes it impossible for me to work on and repair my own vehicle - I think that's illegal or something!

I'm just following the diagnostic procedure in my repair manual. It says the bcm is the Power Mode Master (PMM) and controls all other modules including the pcm (on my truck anyway). The wiring diagrams show there is no direct link between the pcm and the diagnostic link connector, it shows the pcm connects directly to the bcm which then connects to the dlc. The bcm is what receives the ignition switch signal and sends out the signals to all other modules to activate. So if the bcm is dead and sends no signal to anything, the truck would not start. Which means the bcm is what is preventing my truck from starting - according to my repair manual. Believe me, I've been all over this truck checking things and testing. At this point my next step is to replace the bcm. But, I need to know about programming the replacement bcm as I asked above to know what to expect. I have three possible scenarios: 1)I buy a new replacement bcm from my gm dealer, install it, start the truck and drive it to the dealer for programming. 2)I buy a new replacement bcm from my gm dealer, install it, the truck won't start, I have it towed to the dealer for programming. 3)I buy a used replacement bcm from the salvage yard, install it, start the truck and drive it to the dealer for programming. I'm just looking for info from someone who knows for sure which of those scenarios is realistic. Thanks again

Yes, I have verified that. All fuses are good. I have ground at DLC pins 4 and 5 and I have positive voltage at pin 16. Scan tool powers up, but does not communicate. I have also already replaced the ignition switch and nuetral safety switch (PNP) and verified good battery and cables/connections.

Background: I recently purchased a non-running 2003 Chevy Silverado 2500HD 4x4 ext cab with the 6.0 and I've been working to diagnose the problem. I have no signal on the Class 2 serial data line, thus no communication with a code scanner. Following the troubleshooting steps I have isolated the BCM from all other modules on the data line and still have no communication with the BCM. I have checked the wiring for opens, shorts to ground or power, or high resistance and the wiring seems to be fine. So the next step in the troubleshooting procedure is to replace the BCM. GM dealer wants $257 for a new BCM and minimum $90 charge for programming it. Says I have to install the module then bring the truck in to be programmed. Now the questions: If I buy a new BCM through GM and install it, will the truck start and run off the blank un-programmed BCM so I can drive it to the dealer for programming? If that won't work, I can get a used BCM for $75 - will the truck start and run off the used BCM with non-matching VIN (after passlock re-learn)? Can the used BCM then be re-programmed at the dealer to have the proper VIN info and match my truck? Thanks for any help.