No Abs Module Communication 2003 Chev 3500

[Danomite]

Vehicle: 2003 Chev 3500 Flatbed

Gas 6.0l 2WD

 

Hi and thanks in advance. I have used the search function on this forum.

 

I am a tech at a general repair shop. Here's the problem. This vehicle has both the abs light and the brake light on at all times. After disconnecting the battery both lights come on immediately after retstart. I have tried 2 Snap-On and a Tech 2 scanner and neither will communicate with the abs module. All other modules (pcm, airbag etc) do communicate. Fuses ok. Power and ground to abs motor good. Voltage drop from ground wire at abs motor to battery is 0.043 volts, vehicle running. Cleaned 2 large grounds under drivers door on frame. No difference.

 

I have now installed a new dealer abs module and still the same problem. Using a labscope i am not getting any signal from the light blue A9 wire which is the communication wire to the DLC. I have cut the wire to eliminate shorts, and still no digital signal.... am I missing something here or did I receive a defective module?

 

I have not checked the resistance of the pump motor, but it moves briefly when i connect it with the key on...

 

ANY help appreciated!!!

[gmtech4]

you should sublet it to the dealer to have it programed and verified if it got fixed

[Danomite]

you should sublet it to the dealer to have it programed and verified if it got fixed

 

Hi and thanks...I forgot to mention that, that was one of my initial suggestions when the truck first came in....I actually had it at the dealer today briefly to try their scanner and the tech there told me there was no listed reflash to specifically fix a communication problem...there is a tsb for reflashing this abs module, but not specifically for loss of comm...I dunno, maybe he was wrong...

[gmtech4]

the way it works is if I want to update a module with the lastest calibration or software ,I hook it up to the scanner/laptop/pc,go in and click on the proper software and if I click yes to "REprogram" ,it knows what software is already in the modue ,it will not program again what it has already has in the module,so it says ,sorry ,no dice,but to program a new module ,we click on "replace & reprogram"and it will take it every time,like a champion,lol,the tech would know this,p.s ,there is a list for updates to not choose but to accept,so I don't and can't help anymore here than to educate on the proceedure that is typical for programing,wow ,alot of ink I wasted eh?'anywho ,good luck ,ps I hope I didn't confuse you/anyone.

[Danomite]

the way it works is if I want to update a module with the lastest calibration or software ,I hook it up to the scanner/laptop/pc,go in and click on the proper software and if I click yes to "REprogram" ,it knows what software is already in the modue ,it will not program again what it has already has in the module,so it says ,sorry ,no dice,but to program a new module ,we click on "replace & reprogram"and it will take it every time,like a champion,lol,the tech would know this,p.s ,there is a list for updates to not choose but to accept,so I don't and can't help anymore here than to educate on the proceedure that is typical for programing,wow ,alot of ink I wasted eh?'anywho ,good luck ,ps I hope I didn't confuse you/anyone.

 

Ok thanks. So have you seen this being the case with these modules and not communicating? I guess I will send it down for a reflash, thanks so much. I will let you know the result.

[Danomite]

I am trying to check the pump motor and was wondering if you had any specs on its resistance? Thx. Also, can it be checked with the module attached or only with it removed?

[Danomite]

This one is fixed. We removed an alive and a dead rat from this vehicle a couple weeks ago. So I had suspected some chewed wiring....but never found any... Unfortunately is was well hidden, but I found a broken/chewed wire near the engine compartment fuse box. What or where this wire went, I am unsure, but it cured my brakes lights staying on and my communication problem. Thanks for the help.

[gmtech4]

I was looking up specs and went back and read you fixed it ,good for you ,next time ,just punt it to the dealer ,lol,