ok, stopped by shop today, they said they put another new body control module and the computers started communicating again for a few minutes and then quit again. what is possibly that cause?
2001 Silverado lb7 security light and drivers door latch
- Thread starter duramax-rob
- Start date
I got a new update. stopped by today after at least 2.5 weeks sitting outs the mechanic shop in mountain home, Arkansas. owner asked me if I wanted to get it towed out of there and I said no not yet. their tech 2 guy that was gonna show up never showed. just my question, if replacing the 1st body control module with the second one, and the second one worked worked and let their snap-on scanner communicate for a very short time and then quit communicating with scanner.
what else could it be if the body grounds to engine were supposedly taken apart and cleaned. please help if possible. thank you so much!!!!!
im at a loss.
what else could it be if the body grounds to engine were supposedly taken apart and cleaned. please help if possible. thank you so much!!!!!
im at a loss.
Could be another module that won't shut up. Aftermarket radios are known for this. But could be any other. Sometimes you have to disconnect one module at a time and jump the communication pins to complete the circuit. Removing power to the module might work too. One at a time until the network is quiet and you can communicate with the BCM or any remaining modules
thanks 2004lb7. my truck is stock with factory radio. only difference is aftermarket door speakers. I will relay any new replies to the shop next week.
I dont see it or remember but would a TECK 2 scanner work better at diagnosing my trucks problem rather than the SNAP-ON scanner. thanks rob
I dont see it or remember but would a TECK 2 scanner work better at diagnosing my trucks problem rather than the SNAP-ON scanner. thanks rob
Guys, which module is the security system programmed into on a 2001?
I thought the security was handled by the BCM on all years. But I'm not as familiar with the pre 2003 as some others. Maybe the Dash?
I was just thinking that if he replaced the BCM with another and that didn't work out, it's got to be another module. But on an 01, I'm not sure what all modules there are, unlike 03-07 which I'm familiar with.
seems like somewhere I remember reading about if they are 1 or 2 modules. im also gonna repost what happened to my truck from beginning and why I had it towed. im try to get that done in the next day or 2. I really appreciate all the help that everyone has given me for taking time out of their busy schedules!!!!
The newer Up to date snap on scanners are just as capable as a Tech 2 for the most part. As long as he is Identifying the truck correctly it shouldn't be an issue.
The first thing to always check on these is the cigarette lighter fuse. The OBD2 port gets it's power from that circuit. If that is blown it won't read. If that is good, then they need to check the communication wires from the port to the BCM. From there I believe it branches out and communicates with everything else.
No communication is not just powers and grounds. You have to check the Class2 communication wires as well. Some times there is a poor junction or something else that can take the whole thing down. You have to isolate it and work on each system to find the issue.
The first thing to always check on these is the cigarette lighter fuse. The OBD2 port gets it's power from that circuit. If that is blown it won't read. If that is good, then they need to check the communication wires from the port to the BCM. From there I believe it branches out and communicates with everything else.
No communication is not just powers and grounds. You have to check the Class2 communication wires as well. Some times there is a poor junction or something else that can take the whole thing down. You have to isolate it and work on each system to find the issue.
as for as I can find out there doesnt seem to be a separate security module (passlock) only BCM. my system is a passlock only. Im going to post what happened again in numerical order just incase from the beginning I forgot to have missed or order what happened.
)truck sat for 2 days after using and came out and batteries seemed completely dead. no lights, nothing.
)put 1 battery charger 0n passenger side battery thinking that would charge both batteries and it did. security light was on solid.
)tried starting and would only start and die, start and die. drivers door would lock like others but only one that wouldn't unlock.
)drivers door latch had for a while been working hard so I thought latch was bad. waited about 1 week for latch, batteries died again
)replaced door latch, charged batteries again, still same thing happening. day or 2 later dead again.
)borrowed neighbors charger/analyzer showed 1 bad battery. took batteries out one evening, next day go get 2 new and installed.
)now the security light is still on and now no interior lights and other stuff not working, can't remember what else. I think now it wouldn't crank.
)sat now another week then had towed to shop. no communication with their scanner so they replaced BCM. still not communicating.
)now they have dash apart chasing down and looking for broken wire to get no communication problem found
)not sure, but 2nd BCM started to communicate and then quit communicating after short time. then I told them check & clean body grounds.
)they are at a standstill not working on truck. maybe next week or?
Im gonna have them disconnect cables on both batteries and connect + and - for each battery for 10 minutes.. check cigar lighter fuse, then body control fuse, under hood right lower 10amp, check volts on both sides then clean. then check communication wire from port to BCM- class 2. (saw on YouTube). maybe this will help along with any more help from members here!
I hope above is right, as close as memory is. what gets me is that while in posession of truck at start of this, it seemed to get worse when I had both batteries out for replacement or died while working on truck. what problems would that have caused before towed to shop?
thank you all !!!!
)truck sat for 2 days after using and came out and batteries seemed completely dead. no lights, nothing.
)put 1 battery charger 0n passenger side battery thinking that would charge both batteries and it did. security light was on solid.
)tried starting and would only start and die, start and die. drivers door would lock like others but only one that wouldn't unlock.
)drivers door latch had for a while been working hard so I thought latch was bad. waited about 1 week for latch, batteries died again
)replaced door latch, charged batteries again, still same thing happening. day or 2 later dead again.
)borrowed neighbors charger/analyzer showed 1 bad battery. took batteries out one evening, next day go get 2 new and installed.
)now the security light is still on and now no interior lights and other stuff not working, can't remember what else. I think now it wouldn't crank.
)sat now another week then had towed to shop. no communication with their scanner so they replaced BCM. still not communicating.
)now they have dash apart chasing down and looking for broken wire to get no communication problem found
)not sure, but 2nd BCM started to communicate and then quit communicating after short time. then I told them check & clean body grounds.
)they are at a standstill not working on truck. maybe next week or?
Im gonna have them disconnect cables on both batteries and connect + and - for each battery for 10 minutes.. check cigar lighter fuse, then body control fuse, under hood right lower 10amp, check volts on both sides then clean. then check communication wire from port to BCM- class 2. (saw on YouTube). maybe this will help along with any more help from members here!
I hope above is right, as close as memory is. what gets me is that while in posession of truck at start of this, it seemed to get worse when I had both batteries out for replacement or died while working on truck. what problems would that have caused before towed to shop?
thank you all !!!!
Voltage spikes can take out modules. How ever this truck is nearly 25 years old... This stuff was never designed to last this long.
That being said, I personally have not seen the BCM on the GMT800 wiped out from a voltage spike.
The GMT 900 is a different story... It was so common in the past they used to stock them at the dealer and they were only around $100 - $150 for a new one.
If there are any after market accessories wired it they will need to be disconnected. Alarms, radios, CB's,, lights and so on.
From there they will have to Isolate the BCM to the OBD port and work on the connection. Any Good Shop will have access to something like Alldata , Mitchel on demand, or something similar to gain access to wiring diagrams. They will need to trouble shoot it step by step. Any other module could be back feeding Voltage and wiping out the BCM.
That being said, I personally have not seen the BCM on the GMT800 wiped out from a voltage spike.
The GMT 900 is a different story... It was so common in the past they used to stock them at the dealer and they were only around $100 - $150 for a new one.
If there are any after market accessories wired it they will need to be disconnected. Alarms, radios, CB's,, lights and so on.
From there they will have to Isolate the BCM to the OBD port and work on the connection. Any Good Shop will have access to something like Alldata , Mitchel on demand, or something similar to gain access to wiring diagrams. They will need to trouble shoot it step by step. Any other module could be back feeding Voltage and wiping out the BCM.
the only thing i added on was air horns using existing horn wiring with my compressor using relayed fused wire to battery run thru original . 15years ago i had the fast idle using cruise control switch wired into computer wire harness under hood under battery with external off-on switch wired on dash. also electric trailer brake actuater on truck when i got truck. i had a ppe programmer on it years ago not used in years, only used for fault codes and code deletes. thats it, thank you. rob
I had my BCM on my LB7 take a shit when I was soldering some wires and I think I may have shorted something. I suspect a voltage spike did it in.
just wanting to know, the dash ground thats to left of brake hydraulics, one end of ground is on firewall where does the other end of ground wire attach to? thanks. rob
The hood.
thank you!!!
I just assumed you were talking "underhood, looking from the front".
yes i was, thank you. thats not a body ground that would effect any of the problems im having would it.
Not that I know of. IIRC, the grounds for an LB7 are in the harness bolted to the oil pan rail/bottom of block around the front of the engine. Most interior ground issues are a result of bad ground in main connection at drivers side body mount on frame under front door.
thank you SOOO much! im going into town today or tomorrow to actually talk to the mechanicas to what grounds he took apart and cleaned. ill see then if he did that one and make sure he did that! thanks again!!!!!