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 Instructions/Programming | Diagnostic System Check/Starting Point | Schematic |
|---|---|---|---|
| Body Control Module (BCM) | Body Control Module Replacement and Body Control Module (BCM) Programming/RPO Configuration | Diagnostic Starting Point - Body Control System | Body Control System Schematics |
| Electronic Brake Control Module (EBCM) | Electronic Brake Control Module Replacement in Antilock Brake System | Diagnostic System Check - ABS in Antilock Brake System | ABS Schematics in Antilock Brake System |
| Inflatable Restraint Sensing and Diagnostic Module (SDM) | Inflatable Restraint Sensing and Diagnostic Module Replacement in SIR | Diagnostic System Check - SIR in SIR | SIR Schematics in SIR |
| Instrument Panel Cluster (IPC) | Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console | Diagnostic System Check - Instrument Cluster in Instrument Panel, Gages, and Console | Instrument Cluster Schematics in Instrument Panel, Gages, and Console |
| Memory Seat Control Module | Memory Seat Control Module Replacement in Seats | Diagnostic System Check - Power Seat Systems in Seats | Driver Seat Schematics in Seats |
| Powertrain Control Module (PCM) | Powertrain Control Module (PCM) Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L Service Programming System (SPS) in Programming | Diagnostic System Check - Engine Controls in Engine Controls - 4.8L, 5.3L, and 6.0L | Engine Controls Schematics in Engine Controls - 4.8L, 5.3L, and 6.0L |
| Radio | Radio Replacement in Entertainment | Diagnostic System Check - Entertainment System in Entertainment | Radio/Audio System Schematics in Entertainment |
| Remote Control Door Lock Receiver (RCDLR) | Transmitter Programming in Keyless Entry | Diagnostic System Check - Remote Keyless Entry in Keyless Entry | Keyless Entry Schematics in Keyless Entry |
| Roof/Door Module (RDM) | Diagnostic System Check - Power Roof in Roof Diagnostic System Check - Door Systems in Doors | Power Folding Top Schematics in Roof Power Window Schematics in Doors |
Control Module References
Body Control Module (BCM) Setup
Perform the following steps
- Ensure that the battery is fully charged.
- Connect a scan tool to the data link connector (DLC).
- Turn ON the ignition, with the engine and all accessories OFF.
- Program the BCM. Refer to «Service Programming System (SPS)»(ref-187802-S33411820332005090100000) in Programming.
- Perform the «Programming Theft Deterrent System Components»(ref-187812-S19037214622005090100000) in Theft Deterrent.
- Clear all diagnostic trouble codes (DTCs) with the scan tool.
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.
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-187800-S22083178372005090100000) in Instrument Panel, Gages and Console
- Automatic headlamp control, refer to «Exterior Lighting Systems Description and Operation»(ref-187799-S13027051512005090100000) in Lighting Systems
- Interior lighting, refer to «Interior Lighting Systems Description and Operation»(ref-187799-S38139314642005090100000) in Lighting Systems
- Keyless entry (AUO option), refer to «Keyless Entry System Description and Operation»(ref-187809-S17137880092005090100000) in Keyless Entry.
- Passlock theft deterrent, refer to «Vehicle Theft Deterrent (VTD) Description and Operation»(ref-187812-S00138679062005090100000) in Theft Deterrent.
- Retained Accessory Power (RAP), refer to «Retained Accessory Power (RAP) Description and Operation»(ref-187816-S20001967482005090100000) 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 BCM. The BCM uses 3 signals from the ignition switch. These are the Ignition 0 (Unlock), Ignition 1 (Run/Crank), 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 | ||
|---|---|---|---|---|---|
| Ignition Accessory | Ignition 1 (Run/Crank) | Ignition 0 (Unlock) | |||
| OFF | Off-Awake or RAP | No | Inactive | Inactive | Inactive |
| UNLOCK | Unlock or RAP Unlock | No | Inactive | Inactive | Active |
| ACC | Accessory | No | Active | Inactive | Active |
| ON | Run | No | Active | Active | Active |
| START | Crank | No | Inactive | Active | Active |
| ON | Run | Yes | Active | Active | Active |
Correct Ignition Switch Inputs
Fail-Safe Operation
Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the BCM fail to send a power mode message. The fail-safe plan covers modules with discrete ignition signal inputs as well as those modules using exclusively serial data control of power mode.
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 powertrain control module (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.