Body Control System Chevrolet Chevy Express G2500

Fastener Tightening Specifications

Fastener Tightening Specifications

For body control system schematics refer to appropriate SYSTEM WIRING DIAGRAMS article.

Scheme 3

Body Control Module (BCM) - C1 Connector End Connector Part Information 12177194 6-Way F Metri-Pack 150 Series (NA) Pin Wire Color Circuit No. Function A YE 1491 Backlight Lamps Control B PU/WH 1382 LED Dimming Signal C OG 4040 Battery Positive Voltage D OG 1732 Inadvertent Power Supply Voltage E BN/WH 230 Instrument Panel Lamps Dimming Control F RD/WH 2240 Battery Positive Voltage

Body Control Module (BCM) - C2 Connector End Connector Part Information 12110088 24-Way F Micro-Pack 100 Series (GY) Pin Wire Color Circuit No. Function A1-A2 - - Not Used A3 L-BU 244 Passenger Door Lock Switch Lock Control (AU3) A4 PK/WH 1970 Headlamp Low Beam Relay Control A5 WH 111 Hazard Switch Signal A6 D-BU 245 Passenger Door Lock Switch Unlock Control (AU3) A7 L-GN 1391 Driver Door Unlock Relay Control (AU3) A8 L-BU 1344 Cargo Door Release Relay Control (AU3) A9-A10 - - Not Used A11 OG/WH 812 12-Volt Reference A12 RD/WH 1140 Battery Positive Voltage B1 TN/WH 1969 Headlamp High Beam Relay Control B2 WH 1080 Park Lamp Relay Control B3 TN 755 RAP Relay Coil Control (A31) B4 L-GN/BK 592 DRL Low Control B5 - - Not Used B6 BK/WH 351 Ground B7 TN 1835 Security System Sensor Low Reference B8 PK 1348 Headlamp On Indicator Supply Voltage B9 TN 28 Horn Relay Control B10 - - Not Used B11 GY 705 5-Volt Reference B12 L-GN 1037 Class 2 Serial Data

Body Control Module (BCM) - C3 Connector End Connector Part Information 12160778 24-Way F Micro-Pack 100 Series (BN) Pin Wire Color Circuit No. Function A1-A5 - - Not Used A6 YE 1836 Security System Sensor Signal A7 - - Not Used A8 D-GN 306 DRL On/Off Signal A9-A10 - - Not Used A11 PU 328 Interior Lamp Defeat Switch Signal A12 - - Not Used B1 YE 710 Class 2 Serial Data (Early Production) B2 BN/WH 301 Park Lamp Switch On Signal B3-B5 - - Not Used B6 BK/WH 351 Ground B7 - - Not Used B8 OG/BK 2090 Dimming Input B9 L-GN 11 Headlamp Dimmer Switch Signal B10 - - Not Used B11 L-BU 1788 Tow/Haul Switch Signal B12 - - Not Used

Body Control Module (BCM) - C4 Connector End Connector Part Information 12110206 24-Way F Micro-Pack 100 Series (L-BU) Pin Wire Color Circuit No. Function A1 L-GN 80 Key In Ignition Switch Signal A2 YE 307 Headlamp Switch Flash to Pass Signal A3 PK 1020 Ignition 0 Voltage A4 PK 39 Ignition 1 Voltage A5 L-GN 1177 Door Open Switch Signal A6 - - Not Used A7 L-BU 1134 Park Brake Switch Signal A8-A9 - - Not Used A10 YE/BK 1181 Rear Door Open Switch Signal (Passenger/Cargo) A11 - - Not Used A12 WH 103 Headlamp Switch Headlamps On Signal B1-B2 - - Not Used B3 YE 343 Accessory Voltage B4 TN 126 Left Front Door Open Switch Signal B5 L-BU 195 Door Lock Control (AU3) B6 GY/BK 2226 Dimming Return B7-B8 - - Not Used B9 D-BU/WH 1495 Courtesy Lamps On Signal B10 WH 194 Door Unlock Control (AU3) B11-B12 - - Not Used

Body Control Module (BCM) - C5 Connector End Connector Part Information 12177195 6-Way F Metri-Pack 150 Series (BK) Pin Wire Color Circuit No. Function A-C - - Not Used D RD/WH 2140 Battery Positive Voltage E D-BU/WH 149 Courtesy Lamp Supply Voltage - w/o YF7 GY/BK 690 Courtesy Lamp High Control - w/YF7 F L-GN 24 Backup Lamp Supply Voltage

Body Control Module (BCM) - C6 (PRP) Connector End Connector Part Information 12191375 16-Way F Micro-Pack 100 Series (PU) Pin Wire Color Circuit No. Function A1 D-BU/WH 149 Dome Fluorescent Work Lamp Signal (UF2) A2-A6 - - Not Used A7 L-BU 1344 Access Panel Right Side Relay Control A8 GY/BK 690 Dome Fluorescent Work Lamp Relay Control (UF2) B1-B6 - - Not Used B7 L-GN 1391 Access Panel Left Side Rear Relay Control B8 L-BU 244 Access Panel Left Side Front Relay Control

Begin the diagnosis of the body control system by performing the Diagnostic System Check for the system in which the customer concern is apparent. The Diagnostic System Check will direct you to the correct procedure for diagnosing the system and where the procedure is located.

Scan Tool Output Controls

Scan Tool Output Controls

Scan Tool Data List

Scan Tool Data List

Diagnostic Trouble Code (DTC) List

Diagnostic Trouble Code (DTC) List

Circuit Description

Each control module runs a program to detect internal memory faults. No external circuits are involved. If a control module detects any type of internal memory fault, that control module may set DTC B1000.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B1000 Electronic Control Unit (ECU) Performance

Conditions for Running the DTC

1. The control module has power and ground.
2. The ignition is ON.

Conditions for Setting the DTC

DTC B1000 will set if either of the following conditions occur

1. The control module detects an internal write malfunction.
2. The control module detects an internal checksum malfunction.

Action Taken When the DTC Sets

Any of the following actions may occur

1. The control module refuses all additional inputs.
2. The control module requests the Malfunction Indicator Lamp (MIL).
3. The check gages chime sounds.

Conditions for Clearing the DTC

1. A current DTC clears when the ignition is cycled, and the malfunction is no longer present.
2. A history DTC clears when the ignition is cycled 100 times without a repeat of the malfunction.

Diagnostic Aids

1. DTC B1000 may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If DTC B1000 is retrieved as both a current and history DTC, replace the module that set the DTC.

DTC B1000

Some control modules must be configured with serial numbers, vehicle options, or other information. If a control module was not properly configured after installation, that module may set DTC B1001.

This diagnostic procedure supports the following DTC.

DTC B1001 Option Configuration Error

The ignition is ON.

The control module is not configured properly.

1. The SERVICE VEHICLE SOON indicator illuminates.
2. The check gages chime sounds.

1. A current DTC B1001 will clear when the module is correctly programmed.
2. A history DTC B1001 will clear after the ignition has been cycled 100 times, without a repeat of the malfunction.

The most likely reasons for DTC B1001 being set are incorrect calibration files were downloaded to the module, or the module was replaced without the recalibration having been performed.

Test Description

The number below refers to the step number on the diagnostic table.

1. 3: If DTC B1001 is set as current, reprogram the module.

DTC B1001

Each control module runs a program to detect internal memory faults. No external circuits are involved. If a control modules Keep Alive Memory (KAM) has been reset, that control module may set DTC B1004. It is a normal occurrence when battery positive voltage or ground is removed from the module, such as during a battery disconnect.

This diagnostic procedure supports the following DTC

DTC B1004 Keep Alive Memory (KAM) Reset

1. The control module has power and ground.
2. The control module is active/awake.

The KAM in the control module has been reset.

The control module reverts back to the base programmed critical operating data until new data is learned and stored in KAM.

1. A current DTC clears when the ignition is cycled, and the malfunction is no longer present.
2. A history DTC clears when the ignition has been cycled 100 times without a repeat of the malfunction.

1. DTC B1004 may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. DTC B1004 is retrieved as both a current and history DTC, replace the control module.

DTC B1004

Each control module runs a program that tests its ability to write to the Electrically Erasable Programmable Read-Only Memory (EEPROM). No external circuits are involved. The module writes information to a data block in the EEPROM. The module then reads the data and compares it to what was sent to the data block. If the data does not match after 3 consecutive attempts, that control module may set DTC B1007.

This diagnostic procedure supports the following DTC

DTC B1007 EEPROM Write Error

1. The control module has power and ground.
2. The ignition is ON.

The control module detects an EEPROM write error.

The module writes to another area of the EEPROM. This becomes the new permanent area to store the data. The data location is allowed to change until all of the available EEPROM is used. If a B1004 DTC is also set, the module reverts to base operation values programmed for those blocks of data that have failed. The blocks of data that have not failed the checksum test are not affected.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the ignition has been cycled 100 times without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1007

Each control module runs a program to detect internal memory faults. No external circuits are involved. If an Electrically Erasable Programmable Read-Only Memory (EEPROM) checksum error is detected, that control module may set DTC B1009.

This diagnostic procedure supports the following DTC

DTC B1009 EEPROM Checksum Mismatch

1. The control module has power and ground.
2. The ignition is ON.

The control module detects an EEPROM checksum malfunction.

The module reverts to the base operation values programed for those blocks of data that have failed the checksum test. The blocks of data that have not failed the checksum test are not affected.

1. A current DTC clears when the ignition is cycled, and the malfunction is no longer present.
2. A history DTC clears when the ignition has been cycled 100 times without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1009

The Body Control Module (BCM) monitors the battery voltage through the battery positive voltage circuit. If the BCM senses that battery voltage is outside of its normal range for 1 second, DTC B1420 will set.

This diagnostic procedure supports the following DTC

DTC B1420 Device Voltage

The voltage supplied to the body control module is in the range of 7-26 volts.

The voltage supplied to the body control module is in the range of 7-26 volts.

1. The BCM senses a battery voltage above or below the specified range of 9-16 volts.
2. The above condition lasts for at least 1 second.

1. The BCM will disable all its outputs when a high voltage condition is detected.
2. The setting of this DTC inhibits the setting of other DTCs.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the ignition has been cycled 100 times, without a repeat of the malfunction.

1. The following may cause an intermittent: A damaged terminal A backed out terminal A poor terminal tension A chafed wire A broken wire inside the insulation
2. When diagnosing an intermittent short or an open, manipulate the wire harness while watching the test equipment for changes.

DTC B1420

The Body Control Module (BCM) is the Power Mode Master (PMM) responsible for sending ignition switch position information on the class 2 serial data link. The BCM monitors 3 discrete inputs from the ignition switch and the Engine Run Flag (ERF) in order to determine the power mode. The BCM communicates this power mode information to all class 2 modules on the class 2 serial data link. The following table represents correct BCM power mode data

Correct Ignition Switch Inputs

This diagnostic procedure supports the following DTC

DTC B1440 Power Mode Master Input Circuits Mismatch

Battery positive voltage is 9-16 volts.

One of the 3 monitored ignition switch circuits has malfunctioned. The DTC will set if one of the following situations is present

Incorrect Ignition Switch Inputs

The BCM implements default actions for each ignition switch position when faults are detected.

1. A current DTC clears when the malfunction is no longer present for 1 second.
2. A history DTC clears when the ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

DTC B1440

Each control module runs a program to detect internal memory faults. No external circuits are involved. If a memory fault is detected, that control module may set DTC C0550.

This diagnostic procedure supports the following DTC

DTC C0550 Electronic Control Unit (ECU) Performance

1. The control module has power and ground.
2. The ignition is ON.

DTC C0550 will set if either of the following conditions occur

1. The control module detects an internal write malfunction.
2. The control module detects an internal checksum malfunction.

If equipped, the following module specific actions may occur

1. The ABS indicator turns ON.
2. The BRAKE Warning indicator turns ON.
3. The SERVICE 4WD indicator turns ON and the system will be disabled.
4. The SERVICE RIDE SYS or SERVICE RIDE CONTROL message is displayed.
5. The SERVICE SUSPENSION SYS message is displayed.
6. The TCS indicator turns ON.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the ignition is cycled 100 times without a repeat of the malfunction.

1. DTC C0550 may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If DTC C0550 is retrieved as both a current and history DTC, replace the module that set the DTC.

DTC C0550

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the body control system. Refer to «Checking Aftermarket Accessories»(/chevrolet/chevy-express-g2500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__checking-aftermarket-accessories) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

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.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

Power Mode Mismatch

Normal vehicle class 2 communications and module operations will not begin until the system power mode has been identified. Discrete wires from the ignition switch contacts are monitored by the Power Mode Master (PMM) module in order to determine the correct power mode. The PMM communicates the system power mode to all class 2 modules on the class 2 serial data line. Refer to Body Control System Description and Operation to identify which module is the PMM and the applicable power mode look up table.

The numbers below refer to the step numbers on the diagnostic table.

1. 6: This step tests for battery voltage on the signal circuits that are not required.
2. 7: This step tests for no battery voltage on the required signal circuits.
3. 8: If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.
4. 9: This step eliminates open circuits as the cause of the malfunction.

Power Mode Mismatch

Control Module References

Control Module References

Removal Procedure

1. Remove the right side knee bolster trim panel. Refer to «Knee Bolster Replacement - Right»(/chevrolet/chevy-express-g2500/1996-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages, and Console.
2. Disconnect the electrical connectors (2) from the Body Control Module (BCM) (1).
3. Release the tabs (2) retaining the BCM (1) to the bracket.
4. Remove the BCM (1) from the vehicle.

Installation Procedure

1. Install the BCM (1) into the bracket. Ensure the BCM (1) is engaged in the bracket, under the retaining tabs (2).
2. Connect the electrical connectors (2) to the BCM (1).
3. Install the right side knee bolster trim panel. Refer to «Knee Bolster Replacement - Right»(/chevrolet/chevy-express-g2500/1996-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages, and Console.
4. If the BCM has been replaced the module will need to be programed. Program the BCM. Refer to «Body Control Module (BCM) Programming/RPO Configuration»(/chevrolet/chevy-express-g2500/1996-2012/remont/communication-devices/#body-control-system) .

Introduction

The procedure below is designed to set-up the Body Control Module (BCM) correctly after BCM related service. The Service Programming System (SPS) uses the Vehicle Identification Number (VIN) to determine the Regular Production Option (RPO) configuration that the vehicle had when it was built. The SPS programs the BCM with the RPO configuration. After a new BCM is programmed, the Powertrain Control Module (PCM) must learn the new BCM's Passlock fuel enable password. Before you start, read these procedures carefully and completely.

Body Control Module (BCM) Setup

Perform the following steps

1. Ensure that the battery is fully charged.
2. Connect a scan tool to the Data Link Connector (DLC).
3. Turn ON the ignition, with the engine and all accessories OFF.
4. Program the BCM. Refer to «Service Programming System (SPS)»(/chevrolet/chevy-express-g2500/1996-2012/remont/communication-devices/#service-programming-system) in Programming.
5. Perform the «Programming Theft Deterrent System Components»(/chevrolet/chevy-express-g2500/1996-2012/remont/door-locks-anti-theft-systems/#theft-deterrent-system) in Theft Deterrent.
6. 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.

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 (Unlock), Ignition 1 (Run/Crank), and Accessory.

To determine the correct power mode the BCM uses

1. The state of these signals
2. The sequence of switch closures received by the BCM
3. The status of the engine run flag

The chart indicates the power modes detected and transmitted by the BCM

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 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.

See also:
• Master Electrical Component List
• Circuit Testing
• Wiring Repairs
• Battery Inspection/Test (Non-HP2)
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Ignition Switch Replacement
• Checking Aftermarket Accessories
• Testing for a Short to Voltage
• Electronic Brake Control Module Replacement (w/JL4)
• ABS Schematics
• Inflatable Restraint Sensing and Diagnostic Module Replacement
• Diagnostic System Check - SIR
• Instrument Panel Cluster (IPC) Replacement
• Instrument Cluster Schematics
• Powertrain Control Module (PCM) Replacement
• Service Programming System (SPS)
• Diagnostic System Check - Engine Controls
• Diagnostic System Check - Engine Controls
• Engine Controls Schematics
• Engine Controls Schematics
• Radio Replacement
• Radio/Audio System Schematics
• Remote Control Door Lock Receiver Replacement
• Keyless Entry Schematics
• Communication Interface Module Replacement
• Programming Theft Deterrent System Components
• DTC B1000
• Control Module References