Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Control Module References
| Control Module | Repair/Reprogramming Instruction | Diagnostic System Check | Schematic |
|---|---|---|---|
| Audio Amplifier | Refer to Amplifier Replacement in Entertainment | Refer to Diagnostic System Check - Entertainment System in Entertainment | Refer to Radio/Audio System Schematics (non Class 2 Amplifier) or Radio/Audio System Schematics (Class 2 Amplifier) in Entertainment |
| Body Control Module | Refer to Body Control Module Replacement Refer to Body Control Module (BCM) Programming/RPO Configuration | Refer to Body Control System Schematics | |
| Driver Door Module | Refer to Switch Replacement - Door Lock and Side Window - Driver in Doors | Refer to Diagnostic System Check - Door Systems in Doors | Refer to Door Lock/Indicator Schematics in Doors |
| Driver Seat Module | Refer to Memory Seat Control Module Replacement in Seats | Refer to Diagnostic System Check - Power Seat Systems in Seats | Refer to Driver Seat Schematics in Seats |
| Electronic Brake Control Module | Refer to Electronic Brake Control Module Replacement in Anti-lock Brake System | Refer to Diagnostic System Check - ABS in Anti-lock Brake System | Refer to ABS Schematics in Anti-lock Brake System |
| Electronic Suspension Control Module | Refer to Module Assembly Electronic Suspension Control Replacement in Air Suspension | Refer to Diagnostic System Check - Air Suspension in Air Suspension | Refer to Suspension Controls Schematics in Air Suspension |
| Front Passenger Door Module | Refer to Switch Replacement - Door Lock and Side Window - Passenger in Doors | Refer to Diagnostic System Check - Door Systems in Doors | Refer to Door Lock/Indicator Schematics in Doors |
| HVAC Control Module | Refer to HVAC Control Module Replacement in HVAC Systems - Automatic | Refer to Diagnostic System Check - HVAC Systems - Automatic in HVAC Systems - Automatic | Refer to HVAC Schematics in HVAC Systems - Automatic |
| Inflatable Restraint Sensing and Diagnostic Module | Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement in SIR | Refer to Diagnostic System Check - SIR in SIR | Refer to SIR Schematics in SIR |
| Instrument Panel Cluster | Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gauges and Console | Refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gauges and Console | Refer to Instrument Cluster Schematics in Instrument Panel, Gauges and Console |
| Powertrain Control Module | Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L Refer to Service Programming System (SPS) in Programming | Refer to Diagnostic System Check - Engine Controls in Engine Controls - 4.8L, 5.3L, and 6.0L | Refer to Engine Controls Schematics in Engine Controls - 4.8L, 5.3L, and 6.0L |
| Radio | Refer to Radio Replacement in Entertainment | Refer to Diagnostic System Check - Entertainment System in Entertainment | Refer to Radio/Audio System Schematics (non Class 2 Amplifier) or Radio/Audio System Schematics (Class 2 Amplifier) in Entertainment |
| Rear Seat Audio Control | Refer to Audio Control Replacement - Rear Seat in Entertainment | Refer to Diagnostic System Check - Entertainment System in Entertainment | Refer to Radio/Audio System Schematics (non Class 2 Amplifier) or Radio/Audio System Schematics (Class 2 Amplifier) in Entertainment |
| Transfer Case Shift Control Module | Refer to Transfer Case Shift Control Module Replacement in Transfer Case - BW 4484 Refer to Transfer Case Control Module Reprogramming in Transfer Case - BW 4484 | Refer to Diagnostic System Check - Transfer Case in Transfer Case - BW 4484 | Refer to Transfer Case Control Schematics in Transfer Case - BW 4484 |
| Vehicle Communication Interface Module | Refer to Communication Interface Module Replacement in Cellular Communications | Refer to Diagnostic System Check - Cellular Communication in Cellular Communication | Refer to OnStar Schematics in Cellular Communications |
Control Module References
Programming the BCM
| IMPORTANT | After the procedure is completed, the personalization settings of the BCM are set to a default setting. Inform the customer that the personalization must be set again. |
Perform the BCM special function "Request BCM Info. for SPS", then connect the scan tool to SPS terminal. Refer to Service Programming System (SPS) in Programming.
Programming Theft Deterrent System Components
Perform the Programming Theft Deterrent System Components in Theft Deterrent after successfully finishing the Setup New BCM procedure. If the Programming Theft Deterrent System Components in the Theft Deterrent procedure is not performed after a BCM replacement, one of the following conditions will occur
- The vehicle will not be protected against theft by the PASSLOCK system.
- The engine will not crank nor start.
| IMPORTANT | After programming, perform the following to avoid future misdiagnosis |
- Turn the ignition OFF for 10 seconds.
- Connect the scan tool to the data link connector.
- Turn the ignition ON with the engine OFF.
- Use the scan tool in order to retrieve history DTCs from all modules.
- Clear all history DTCs.
BCM Functions
The body control module (BCM) performs multiple body control functions. The BCM can control devices directly connected to its outputs based on input information. The BCM evaluates this information and controls certain body control systems by commanding outputs on or off. The BCM control inputs can be
- Sensors and switches that are directly connected to the BCM
- Class 2 serial data received from other control modules connected to the class 2 serial data link.
The BCM is also capable of controlling other vehicle systems that are not directly wired to the BCM. The BCM does this by sending specific messages on the class 2 serial data link. The control module capable of performing the required function will respond to the BCM message.
The BCM controls these functions
- Audible warnings - Refer to «Audible Warnings Description and Operation»(ref-187217-S39281842872005083100000) in Instrument Panel, Gauges and Console
- Automatic door locks - Refer to «Power Door Locks Description and Operation»(ref-187212-S11752284712005083100000) in Doors
- Automatic headlamp control - Refer to «Exterior Lighting Systems Description and Operation»(ref-187211-S37657540532005083100000) in Lighting Systems
- Interior lighting - Refer to «Interior Lighting Systems Description and Operation»(ref-187211-S34235336252005083100000) in Lighting Systems
- Keyless entry (AUO option) - Refer to «Keyless Entry System Description and Operation»(ref-187226-S41111950322005083100000) in Keyless Entry.
- Passlock theft deterrent - Refer to «Vehicle Theft Deterrent (VTD) Description and Operation»(ref-187232-S19557290142005083100000) in Theft Deterrent.
- Retained accessory power (RAP) - Refer to «Retained Accessory Power (RAP) Description and Operation»(ref-187237-S00040938922005083100000) in Retained Accessory Power
Serial Data Power Mode
On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle the PMM is the body control module (BCM). The BCM uses 3 signals from the ignition switch. These are the Ignition 0, Ignition 1, and Accessory.
To determine the correct power mode the BCM uses
- The state of these signals
- The sequence of switch closures received by the BCM
- The status of the engine run flag
The chart indicates the power modes detected and transmitted by the BCM
| Ignition Key Position | Power Mode Parameter | Engine Running | Sampled Ignition Signal State | ||
|---|---|---|---|---|---|
| Accessory | Ignition 1 | Ignition 0 | |||
| OFF | Off-Awake or RAP | No | Inactive | Off | Off |
| UNLOCK | Unlock or RAP Unlock | No | Inactive | Off | On |
| ACC | Accessory | No | Active | Off | On |
| ON | Run | No | Active | On | On |
| START | Crank | No | Inactive | On | On |
| ON | Run | Yes | Active | On | On |
Correct Ignition Switch Inputs
Serial Data Messages
The modules that depend exclusively on serial data messages for power modes stay in the state dictated by the last valid BCM message until they receive the engine status from the PCM. If the BCM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is true, indicating that the engine is running, the modules fail-safe to Run. In this state the modules and their subsystems can support all operator requirements. If the engine run flag serial data is false, indicating that the engine is not running, the modules fail-safe to OFF-AWAKE. In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.
Discrete Ignition Signals
Those modules that have discrete ignition signal inputs also remain in the state dictated by the last valid BCM message received on the serial data circuits. They then check the state of their discrete ignition input to determine the current valid state. If the discrete ignition input is active, B+, the modules will fail-safe to the RUN power mode. If the discrete ignition input is not active, open or 0 voltage, the modules will fail-safe to OFF-AWAKE. In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.