GM LS Engine - Body Control Module Screw Up

[jaredvh]

The other day I was installing some stereo equipment and had the battery disconnected on my 2007 Silverado 6.0. When I was done I reconnected it and jumped in the truck and when I turned the key it didnt start. No cranking or clicking or anything. The dash read "Service 4 wheel drive", and the CEL, ABS and Traction control lights were on. The gear indicator read PRND321 but there was no marker to show which gear the truck was in. The only accessories that would work of the whole bunch I tried were my power mirrors, stereo, front windows, power seats and OnStar. I spent hours online trying to find the problem but there was very limited information hence the reason I am making this post. Finally I had it towed into the dealership where they spent a few hours and eventually diagnosed that the body control module had gone screwy hand had to be reprogrammed. $100 tow bill and $365 Pike Wheaton bill and the truck is back on the road. Apparently once in a while the BCM decides to lose its memory when there is a voltage fluctuation.

Anyways, Just thought I'd post to help anybody else who may come across this issue before you waste a bunch of time searching and checking over everything like I did.

 

[Summitric]

Yup, we've had a few do that...... Not cheap

 

[jaredvh]

Its a hassle more than anything! Haha. New vehicle electronics do funny things sometimes.

 

[Summitric]

Yep, and there's no rhyme or reason why......... And some people just can't understand that

 

[oler1234]

interesting... what is the body control module?? what does it do?? i own a 1500 6.0l myself

 

[kbrunlees]

it controls everything, you never want to screw with it or even look at it sideways wrong. When they work they work great but screw with it and you get the big bill. It is slightly larger than a stereo and sits inside the dash.

 

[jaredvh]

I think... feel free to correct me if I'm wrong, but it communicates with all the different electronic components of the vehicle and controls their operation.

I guess they serve their purpose but throw weird codes when they mess up and theres not a lot you can do to prevent it.

 

[Summitric]

Body Control System Description and Operation

The body control system consists of the body control module (BCM), communications, and various input and outputs. Some inputs, outputs and messages require other modules to interact with the . The BCM also has discrete input and output terminals to control the vehicle's body functions. The BCM is wired to the GMLAN high speed serial data buss and the GMLAN low speed serial data buss and acts as a gateway between them. If the BCM does not communicate the vehicle will not start due to the inability of the engine control module (ECM)/powertrain control module (PCM) and theft deterrent module (TDM) to communicate without the BCM providing the gateway function.

Power Mode Master

This vehicles body control module (BCM) functions as the power mode master (PMM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determination the power mode that will be sent over the serial data circuits to the other modules that need this information, and so the PMM will activate relays and other direct outputs of the PMM as needed. Refer to Power Mode Description and Operation for a complete description of power mode functions.

Serial Data Gateway

The body control module (BCM) in this vehicle functions as a gateway or translator. The purpose of the gateway is to translate serial data messages between the GMLAN high speed buss and the GMLAN low speed buss for communication between the various modules. The gateway will interact with each network according to that network's transmission protocol.

One example of this necessary communication is the communication between the engine control module (ECM)/powertrain control module (PCM) which is high speed serial data and Theft Deterrent Module which is low speed serial data. If these modules can not exchange information, the vehicle will not start.

Communication between the and a scan tool can be on the high speed GMLAN network or low speed GMLAN network. If one network is lost, the BCM can still communicate with the scan tool. A lost communication DTC typically is set in modules other than the module with a communication failure.



The various body control module (BCM) input and output circuits are described in the corresponding functional areas indicated on the electrical schematics. Some BCM functions with the subsystems may be as a gateway only or as an enable for the system. The BCM related systems/subsystems include, but are not limited to the following:

• Antilock Brake System (ABS)-Refer to ABS Description and Operation (Under 8600 GVW) ABS Description and Operation (Equal to or Over 8600 GVW).
• Automatic Day-Night Mirror-Refer to Automatic Day-Night Mirror Description and Operation.
• Cruise Control System-Refer to Cruise Control Description and Operation.
• Electrical Power Management (EPM)-Refer to Electrical Power Management Description and Operation.
• Exterior Lighting-Refer to Exterior Lighting Systems Description and Operation.
• Horn System-Refer to Horns System Description and Operation.
• HVAC-Refer to Air Delivery Description and Operation and Air Temperature Description and Operation.
• Instrument Cluster Indicator Control-Refer to Instrument Cluster Description and Operation.
• Interior Lighting-Refer to Interior Lighting Systems Description and Operation.
• Power Door Lock System-Refer to Power Door Locks Description and Operation.
• Rear Window Defogger System-Refer to Rear Window Defogger Description and Operation.
• Redundant Steering Wheel Controls-Refer to Steering Wheel Controls Description and Operation.
• Remote Function Actuation (RFA) Control-Refer to Keyless Entry System Description and Operation.
• Retained Accessory Power (RAP)-Refer to Retained Accessory Power (RAP) Description and Operation.
• Shift Lock Control System-Refer to Automatic Transmission Shift Lock Control Description and Operation.
• Starting System-Refer to Starting System Description and Operation.
• Supplemental Inflatable Restraint (SIR) System-Refer to SIR System Description and Operation.
• Theft Deterrent-Refer to Content Theft Deterrent (CTD) Description and Operation.
• Tire Pressure Monitor (TPM) System-Refer to Tire Pressure Monitor Description and Operation.
• Wiper/Washer System Functions-Refer to Wiper/Washer System Description and Operation.

Export

The export body control system has an additional located in the rear of the vehicle. This additional body control module is referred to as the XBCM. The XBCM has discrete input and output terminals to control additional vehicle body functions not supported by the primary body control module (BCM). The XBCM is wired to the GMLAN low speed serial data buss and the BCM and acts as a gateway between them. If the XBCM does not communicate, various rear end lighting such as rear fog lamps and trailer lighting will be impaired.

The various input and output circuits are described in the corresponding functional areas indicated on the XBCM electrical schematics. Some XBCM functions with the subsystems may be as a gateway only or as an enable for the system. The XBCM related systems/subsystems include, but are not limited to the following:

• Exterior lighting-Refer to Exterior Lighting Systems Description and Operation.
• Instrument cluster indicator control-Refer to Instrument Cluster Description and Operation.
• Theft deterrent-Refer to Content Theft Deterrent (CTD) Description and Operation

 

[Summitric]

Jus' sayin'