Body Control Modules Chevrolet Cavalier III

DESCRIPTION

The Body Control Module (BCM) controls many vehicle functions. These functions include A/C compressor, audible warnings (chime), battery rundown protection, instrument panel cluster indicators and gauges, interior and exterior lighting, theft deterrent, keyless entry, rear compartment release, shift lock control (A/T) and panic horn.

The BCM communicates with other systems over a serial data line to execute various vehicle functions. Communication between each system is accomplished by sending digitally coded messages, which consist of specific information the system module must follow. Each system module is assigned its own recognition code, so that it can respond to appropriate messages.

Other modules that communicate with the BCM over this line are the Electronic Brake Control Module (EBCM), Powertrain Control Module (PCM), Instrument Panel Cluster (IPC) and the inflatable restraint Sensing and Diagnostic Module (SDM).

A/C COMPRESSOR

The Body Control Module (BCM) receives an A/C request signal from heater-A/C control panel and transmits this signal over the class 2 serial data line to the Powertrain Control Module (PCM). The PCM engages the A/C compressor clutch.

ASLEEP & AWAKE FUNCTIONS

Wake up signals turn Body Control Module (BCM) on to begin controlling and/or monitoring of certain functions. BCM wake-up inputs are as follows

1. Door ajar switches.
2. Ignition switch actuation.
3. Inadvertent power feedback.
4. Driver door lock actuation.
5. Trunk release.

AUDIBLE WARNINGS (CHIME)

Body Control Module (BCM) sends chime signal to radio. Radio receives signal and emits chime through speakers. The BCM determines the priority of the chime requests. The highest priority chime request is activated. Only one chime may be on at a given time. For simultaneous chime conditions, the BCM completes all of the pending low priority chimes after completing the higher priority chimes. The functions which cause the chime to be activated are listed from lowest to highest priority.

1. Automatic Door Lock (Delayed Locking Verification)
2. Automatic Door Lock (Programming Option Verification)
3. Check Gauges
4. Headlights Left On (Ignition Off)
5. Key Left In The Ignition
6. Oil Life Reset
7. Parking Brake On (Vehicle Moving)
8. Tire Inflation Monitoring System (TIMS) Reset
9. Turn Signal Left On
10. Seat Belt Not Fastened

AUTOMATIC TRANSAXLE SHIFT LOCK CONTROL

Body Control Module (BCM) controls shift lock function by supplying system ground. Shift lock is released when ignition is on and brake is applied. See appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS.

BATTERY RUNDOWN PROTECTION

Body Control Module (BCM) helps to prevent inadvertent battery rundown from courtesy lights left on. The BCM monitors current draw on the courtesy light circuit and will interrupt power to the courtesy lights to minimize battery drain. When ignition is turned off, a time-out period of 20 minutes begins. After 20 minutes, the inadvertent output is turned off. When the BCM receives a wake up signal, it will turn the output back on and reset time-out period.

CLASS 2 SERIAL DATA LINE

The class 2 serial data line is a Purple wire connected between Data Link Connector (DLC) terminal No. 2 and the following modules.

1. Body Control Module (BCM)
2. Electronic Brake Control Module (EBCM)
3. Instrument Panel Cluster (IPC)
4. Powertrain Control Module (PCM)
5. Inflatable Restraint Sensing And Diagnostic Module (SDM)
6. Radio

The class 2 serial data line allows these modules to communicate with each other and with the scan tool for diagnostic and testing purposes.

DAYTIME RUNNING LIGHTS

Body Control Module (BCM) controls Daytime Running Lights (DRL) function by supplying system ground. DRL is activated when park brake is off, transaxle is not in Park and headlight switch is off.

DRIVER WARNING

BCM is responsible for interpreting most of the indicators. BCM receives inputs and sends to the instrument cluster the following messages.

1. Theft System
2. Low Engine Coolant
3. High Beam
4. Service Engine Soon
5. Daytime Running Lights (DRL)
6. Brake
7. Traction Off
8. Check Gauges

REMOTE KEYLESS ENTRY

Body Control Module (BCM) controls all remote keyless entry functions. See REMOTE KEYLESS ENTRY SYSTEMS - CAVALIER & SUNFIRE article.

COMPONENT LOCATIONS

COMPONENT LOCATIONS

BCM PROGRAMMING/REGULAR PRODUCTION OPTION CODES

Body Control Module (BCM) must be programmed with proper Regular Production Option (RPO) configurations. If BCM is not properly programmed with correct RPO codes, the BCM will not be able to control the features properly. Before programming BCM ensure battery is fully charged, ignition switch is in ON position and the Data Link Connector (DLC) is accessible. Using scan tool, select SPECIAL FUNCTIONS and NEW BCM SETUP. Follow instructions on scan tool to program BCM. If BCM fails to accept programming or RPO codes, check connections at BCM and ensure scan tool has latest software updates. When BCM, Powertrain Control Module (PCM) or Passlock(tm) sensor are replaced, Passlock(tm) sensor must also be reprogrammed. See PASSWORD LEARN PROCEDURE .

PASSWORD LEARN PROCEDURE

Note. Password must be learned when Passlock(tm) sensor, Body Control Module (BCM) or Powertrain Control Module (BCM) is replaced. BCM must be programmed with proper Regular Production Option (RPO) configurations before preforming relearn procedures. If PCM is replaced, after programming, PCM will immediately learn the first password it receives. If password needs to be changed, learn procedure will need to be performed.

1. Clear all DTCs. Turn ignition off. Replace component(s) as necessary.
2. With transmission in Park (A/T) or Neutral (M/T), turn ignition switch momentarily to START position (engine will not start). Leave ignition in RUN position (engine off). If Passlock(tm) sensor was replaced, SECURITY indicator light will flash for 10 minutes. If Passlock(tm) module was replaced, SECURITY indicator light will flash for a few seconds, then stay on for 10 minutes. If PCM was replaced with a new PCM, vehicle may start and procedure may not be needed. If replacement PCM was used even momentarily, SECURITY indicator light will flash for a few seconds, then stay on for 10 minutes. After 10 minutes, when light turns off, turn ignition switch to OFF position for 5 seconds.
3. Repeat step 2 twice more. Ignition switch must be turned to OFF position. Auto learn procedure will be completed during next start attempt. Clear all DTCs.

SELF-DIAGNOSTIC SYSTEM

Note. Do not replace the Body Control Module (BCM) unless a DTC remains current after all DTC repair procedures have been performed. Do not replace BCM based on history DTCs.

Body Control Module (BCM) is equipped with a self-diagnostic system, which detects system Diagnostic Trouble Codes (DTCs) or abnormalities. When a malfunction occurs, BCM will store a DTC. See BODY CONTROL SYSTEM DIAGNOSTIC TROUBLE CODE INDEX table. Malfunctions are recorded as history/intermittent failures or as current failures. Current DTCs indicate BCM has detected a fault which is currently present. A history DTC indicates that BCM has previously detected a malfunction that is not currently present.

BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK

1. Connect scan tool to Data Link Connector (DLC). If scan tool powers up, go to next step. If scan tool does not power up, go to «SCAN TOOL DOES NOT POWER UP»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__scan-tool-does-not-power-up) .
2. Turn ignition on. Attempt to establish communication with Body Control Module (BCM). If scan tool communicates with BCM, go to next step. If scan tool does not communicate with BCM, go to «SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) .
3. If any communication DTCs exist (DTCs beginning with a "U"), go to «SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) . If no communication DTCs exist, perform appropriate test. See «BODY CONTROL SYSTEM DIAGNOSTIC TROUBLE CODE INDEX»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) table.

BODY CONTROL SYSTEM DIAGNOSTIC TROUBLE CODE INDEX

Modules connected to class 2 serial data circuit monitor serial data communications during normal vehicle operation. Operating information and commands are exchanged between modules. Connecting scan tool to Data Link Connector (DLC) allows communication with modules for diagnostics. The engine will not start when there is a complete malfunction of class 2 serial data line while engine is off.

Testing

1. Connect scan tool to Data Link Connector (DLC). If scan tool powers up, go to next step. If scan tool does not power up, go to «SCAN TOOL DOES NOT POWER UP»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__scan-tool-does-not-power-up).
2. Turn ignition on. Attempt to communicate with each module on class 2 serial data circuit. If scan tool communicates with one or more modules, go to next step. If scan tool does not communicate with any module, go to step 6.
3. Retrieve DTCs for each module. Record DTCs, DTC status and which module set the DTC(s). If any DTCs between DTC U1000 and U1255 are set, go to next step. If any DTCs between DTC U1000 and U1255 are not set, go to step 5.
4. If only DTC U1000 is set, go to «DTC U1000 OR U1255: CLASS 2 COMMUNICATION MALFUNCTION»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under DIAGNOSTIC TESTS. If DTC U1000 is not the only DTC set, go to «DTC U1001-U1254 LOSS OF COMMUNICATIONS WITH XXX»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under DIAGNOSTIC TESTS.
5. Diagnose fault. See «DTC U1001-U1254: LOSS OF COMMUNICATIONS WITH XXX»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under DIAGNOSTIC TESTS.
6. Turn ignition off. Disconnect scan tool from DLC. Inspect DLC terminals No. 2 and 5 for poor connections and terminal tension. (Scheme 1) If terminals are okay, go to next step. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
7. Check for open circuit between DLC terminal No. 5 (Black/White wire) and ground point G102, located on steering column support. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. If circuit is okay, go to next step. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
8. Check for open in Purple wire between DLC terminal No. 2 and BCM harness connector C2 terminal B7. If circuit is okay, go to next step. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
9. Disconnect Powertrain Control Module (PCM) harness connector C1. Disconnect radio harness connector C1. Disconnect Instrument Panel Cluster (IP) harness connector C1. Connect scan tool to DLC. Turn ignition on. Attempt to communicate with BCM on class 2 serial data circuit. If scan tool communicates with BCM, go to next step. If scan tool does not communicate with BCM, go to step 11.
10. Turn ignition off. Disconnect Electronic Brake Control Module (EBCM) harness connector. Connect PCM connector C1. Turn ignition on. Attempt to communicate with BCM or PCM on class 2 serial data circuit. If scan tool communicates with BCM or PCM, go to step 12. If scan tool does not communicate with BCM and PCM, go to step 13.
11. Turn ignition off. Check for short to ground and short to voltage in Purple wire between DLC connector terminal No. 2 and BCM harness connector C2 terminal B7. Check for short to ground and short to voltage in Purple wire between IPC harness connector terminal "L" and BCM harness connector C2 terminal B9. Check for short to ground and short to voltage in Purple wire between IPC harness connector terminal "K" and SDM harness connector terminal A5. Check for short to ground and short to voltage in Purple wire between SDM harness connector terminal A4 and EBCM harness connector C1 terminal B7. Check for short to ground and short to voltage in Purple wire between EBCM harness connector C1 terminal C8 and PCM harness connector C1 terminal No. 58. Check for short to ground and short to voltage in Purple wire between BCM harness connector C2 terminal B8 and PCM harness connector C1 terminal No. 59. Check for short to ground and short to voltage in Purple wire between BCM harness connector C1 terminal B8 and radio harness connector C1 terminal A1. If no shorts are found on class 2 serial data circuits, go to step 16. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
12. Turn ignition off. Connect IPC connector. Disconnect Sensing and Diagnostic Module (SDM) harness connector. Turn ignition on. Attempt to communicate with BCM, IPC or PCM on class 2 serial data circuit. If scan tool communicates with BCM, IPC or PCM, go to step 14. If scan tool does not communicate with BCM and PCM, go to step 15.
13. Turn ignition off. Check for short to ground and short to voltage in Purple wire between EBCM harness connector C1 terminal C8 and PCM harness connector C1 terminal No. 58. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check). If no problems are found, go to step 17.
14. Turn ignition off. Connect SDM harness connector. Turn ignition on. Attempt to communicate with BCM, IPC, PCM or SDM on class 2 serial data circuit. If scan tool communicates with BCM, IPC, PCM or SDM, go to step 21. If scan tool does not communicate with BCM, IPC, PCM or SDM, go to step 19.
15. Turn ignition off. Check for short to ground and short to voltage in Purple wire between IPC harness connector terminal "K" and SDM harness connector terminal A5. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check). If no problems are found, go to step 18.
16. Check BCM connectors for poor connections and terminal tension. If terminals are okay, go to step 24. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
17. Check PCM connectors for poor connections and terminal tension. If terminals are okay, go to step 25. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
18. Check IPC connectors for poor connections and terminal tension. If terminals are okay, go to step 26. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
19. Turn ignition off. Check for short to ground and short to voltage in Purple wire between SDM harness connector terminal A4 and EBCM harness connector C1 terminal B7. If no problems are found, go to next step. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
20. Check SDM connectors for poor connections and terminal tension. If terminals are okay, go to step 27. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
21. Turn ignition off. Connect EBCM harness connector. Turn ignition on. Attempt to communicate with BCM, EBCM, IPC, PCM or SDM on class 2 serial data circuit. If scan tool communicates with BCM, EBCM, IPC, PCM or SDM, go to next step. If scan tool does not communicate with BCM, EBCM, IPC, PCM or SDM, go to step 23.
22. Check radio connectors for poor connections and terminal tension. If terminals are okay, go to step 28. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
23. Check EBCM connectors for poor connections and terminal tension. If terminals are okay, go to step 29. If any problem is found, repair as necessary and go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check).
24. Replace BCM. See «BODY CONTROL MODULE»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under REMOVAL & INSTALLATION. Program BCM. See «PROGRAMMING»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules). After repairs, go to step 30.
25. Replace PCM. See «POWERTRAIN CONTROL MODULE»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under REMOVAL & INSTALLATION. After repairs, go to step 30.
26. Replace instrument panel cluster. See «INSTRUMENT PANEL CLUSTER»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under REMOVAL & INSTALLATION. After repairs, go to step 30.
27. Replace SDM. See «SENSING & DIAGNOSTIC MODULE (SDM)»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under REMOVAL & INSTALLATION. After repairs, go to step 30.
28. Replace radio. After repairs, go to step 30.
29. Replace EBCM. See «ELECTRONIC BRAKE CONTROL MODULE (EBCM)»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__electronic-brake-control-module-ebcm) under REMOVAL & INSTALLATION. After repairs, go to next step.
30. Reconnect all harness connectors. Connect scan tool to DLC. Turn ignition on. Wait 10 seconds. Scan tool may require a power up reset before communication will occur if class 2 serial data circuit was shorted. Turn off or disconnect scan tool. Reconnect scan tool and retrieve DTCs from each module. Record DTCs and DTC status. If any current DTCs beginning with a "U" are present, go to step 32. If no current DTCs beginning with a "U" are present, go to next step.
31. If any DTCs not beginning with a "U" are present, go to next step. If no DTCs not beginning with a "U" are present, go to step 34.
32. Perform appropriate diagnostic procedure. See «BODY CONTROL SYSTEM DIAGNOSTIC TROUBLE CODE INDEX»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) table. For DTCs not listed, attempt to diagnose malfunctioning system or device by symptom. Go to appropriate article for malfunctioning system or device. After repair, go to next step.
33. If all DTCs have been diagnosed, go to next step. If any DTCs have not been diagnosed, go to step 32.
34. Using scan tool, clear DTCs. System is okay at this time.

Scheme 1

Scheme 2

Scheme 3

SCAN TOOL DOES NOT POWER UP

1. Check for battery voltage at DLC terminal No. 16 (Orange wire). (Scheme 1) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short to ground in Orange wire between DLC and CIG fuse (20-amp) located in left Instrument Panel (IP) junction block. After repairs, go to step 5.
2. Check for open in Black wire between DLC terminal No. 4 and ground point G204. (Scheme 1) Repair as necessary and go to step 5. If ground circuit is okay, go to next step.
3. Check for poor connections between scan tool and DLC terminals No. 4 and 16. (Scheme 1) Repair as necessary and go to step 5. If no problems are found, go to next step.
4. Scan tool may be malfunctioning. Check scan tool manual for diagnostic procedures. After repairs, go to next step.
5. Perform diagnostic system check. See «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check). If referred from another article, return to that article and perform diagnostic system check.

Body Control Module (BCM) performs a self-test when ignition is turned on. If BCM detects an internal error, DTC B1000 sets, SERVICE VEHICLE SOON light turns on and the check gauges chime sounds.

1. If body control system diagnostic system check has been performed, go to next step. If body control system diagnostic system check has not been performed, go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. If DTC B1000 is set as current, replace BCM. If DTC B1000 is not set as current, system is okay at this time.

Circuit Description

Body Control Module (BCM) can be configured with applicable vehicle options. DTC B1001 will set if BCM was not configured either at assembly plant or after replacement.

1. If body control system diagnostic system check has been performed, go to next step. If body control system diagnostic system check has not been performed, go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Reprogram BCM. See «BCM PROGRAMMING/REGULAR PRODUCTION OPTION CODES»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__bcm-programmingregular-production-option-codes) under PROGRAMMING.

DTC B1372 will set if IGNITION 1 input is not active after engine has been running for 20 seconds. When DTC is present, SERVICE VEHICLE SOON indicator will turn on and check gauges chime will sound. A current DTC B1372 will clear when fault is no longer present and ignition switch is cycled.

1. If body control system diagnostic system check has been performed, go to next step. If body control system diagnostic system check has not been performed, go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Observe IGNITION 1 input on BCM data list. If scan tool indicates ON, go to «DIAGNOSTIC AIDS»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__diagnostic-aids) . If scan tool does not indicate ON, go to next step.
3. Check BCM/CLU fuse (10-amp) located in instrument panel fuse block. If fuse is blown, go to next step. If fuse is okay, go to step 7 .
4. Connect test light between BCM/CLU fuse terminals. Turn ignition on. If test light comes on, go to next step. If test light does not come on, go to «DIAGNOSTIC AIDS»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__diagnostic-aids) .
5. Turn ignition off. Disconnect BCM connector C3. Turn ignition on. If test light comes on, go to next step. If test light does not come on, go to step 11 .
6. Turn ignition off. Disconnect instrument cluster harness connector. Turn ignition on. If test light comes on, go to step 9 . If test light does not come on, go to step 12 .
7. Remove BCM/CLU fuse. Turn ignition on. With test light connected to ground, probe both terminals of BCM/CLU fuse. If test light comes on at one terminal, go to next step. If test light does not come on at either terminal, go to step 10 .
8. Check for open in Pink wire between instrument panel fuse block and BCM connector C3 terminal A12. Repair as necessary and go to step 15 . If circuit is okay, go to step 13 .
9. Repair short to ground in Pink wire between instrument panel fuse block and BCM connector C3 terminal A12. After repairs, go to step 15 .
10. Repair short to ground in Pink wire between underhood junction block and ignition switch. See POWER DISTRIBUTION article in WIRING DIAGRAMS. After repairs, go to step 15 .
11. Check for poor connections at BCM connector. If connector is okay, go to step 13 . If problem is found, repair as necessary. After repair, go to step 15 .
12. Check for poor connections at instrument cluster connector. If connector is okay, go to step 14 . If problem is found, repair as necessary. After repair, go to step 15 .
13. Replace BCM. See «BODY CONTROL MODULE»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under REMOVAL & INSTALLATION. Program BCM. See «PROGRAMMING»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) . After repairs, go to step 15 .
14. Replace instrument cluster. See «INSTRUMENT PANEL CLUSTER»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under REMOVAL & INSTALLATION. After repairs, go to next step.
15. Using scan tool, clear DTCs. Turn ignition off, then start engine. Wait 20 seconds, and retrieve DTCs. If DTC resets, go to step 2 . If DTC does not reset, system is okay at this time.

Diagnostic Aids

If DTC is history, problem may be intermittent. Perform test procedure while wiggling wiring and connectors.

DTC B1382 will set if IGNITION ACC is not active after IGNITION 1 has been active for 20 seconds. When DTC is present, SERVICE VEHICLE SOON indicator will turn on and check gauges chime will sound. A current DTC B1382 will clear when fault is no longer present and ignition switch is cycled.

1. If body control system diagnostic system check has been performed, go to next step. If body control system diagnostic system check has not been performed, go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Observe ACCESSORY input on Body Control Module (BCM) data list. If scan tool does not indicate ON, go to next step. If scan tool indicates ON, go to «DIAGNOSTIC AIDS»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) .
3. Remove and check BCM fuse (10-amp) located in Instrument Panel (IP) junction block. If fuse is blown, go to next step. If fuse is okay, go to step 6 .
4. Connect test light between BCM fuse (10-amp) terminals in IP junction block. Turn ignition on. If test light comes on, go to next step. If test light does not come on, go to «DIAGNOSTIC AIDS»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) .
5. Turn ignition off. Disconnect BCM connector C2. Turn ignition on. If test light comes on, go to step 8 . If test light does not come on, go to step 10 .
6. Remove BCM fuse from IP junction block. Turn ignition on. With test light connected to ground, probe both terminals of BCM fuse. If test light comes on at one terminal, go to next step. If test light does not come on at either terminal, go to step 9 .
7. Check for open in Yellow wire between IP junction block and BCM connector C2 terminal A3. See POWER DISTRIBUTION article in WIRING DIAGRAMS. Repair as necessary and go to step 12 . If circuit is okay, go to step 11 .
8. Repair short to ground in Yellow wire between IP junction block and BCM connector C2 terminal A3. See POWER DISTRIBUTION article in WIRING DIAGRAMS. After repairs, go to step 12 .
9. Repair open in Brown wire between right IP junction block (BCM fuse) and ignition switch connector C2 terminal "A". See POWER DISTRIBUTION article in WIRING DIAGRAMS. After repairs, go to step 12 .
10. Check for poor connections at BCM connector. If connector is okay, go to next step. If any problem is found, repair as necessary and go to step 12 .
11. Replace BCM. See «BODY CONTROL MODULE»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under REMOVAL & INSTALLATION. Program BCM. See «PROGRAMMING»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) . After repairs, go to step 12 .
12. Using scan tool, clear DTCs. Turn ignition off and on. Wait 20 seconds, and retrieve DTCs. If DTC B1382 resets, go to step 2 . If DTC does not reset, system is okay at this time.

If DTC is history, problem may be intermittent. Perform test procedure while wiggling wiring and connectors.

Body Control Module (BCM) monitors circuit No. 80 (Light Green wire) to determine if key is in ignition. DTC B2965 will set if key-in-ignition input is not active after ignition has been on for 20 seconds. When DTC is present, BCM assumes key-in-ignition input is active and interior lights will not turn on after key is removed from ignition switch.

1. If body control system diagnostic system check has been performed, go to next step. If body control system diagnostic system check has not been performed, go to «BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__body-control-system-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Observe KEY-IN-IGNITION input on BCM data list. If scan tool displays YES, go to next step. If scan tool does not display YES, go to step 4.
3. While monitoring KEY-IN-IGNITION input on BCM data list, insert and remove key from switch several times. If KEY-IN-IGNITION changes each time, problem is not current. See «DIAGNOSTIC AIDS»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules). If KEY-IN-IGNITION does not change each time, go to step 6.
4. Turn ignition off. Disconnect BCM connector C3. Turn ignition on. Connect a test light between battery positive terminal and BCM harness connector C3 terminal B12 (Light Green wire). (Scheme 3) If test light comes on, go to step 8. If test light does not come on, go to next step.
5. Turn ignition off. Disconnect ignition switch connectors C1 and C2. Check continuity of Light Green wire between BCM harness connector C3 terminal B12 and ignition switch connector C2 terminal "F". Check continuity between ignition switch connector C1 terminal "F" (Black wire) and ground. If continuity exists on both circuits, go to step 9. If continuity is not present on either circuit, repair as necessary. After repair, go to step 12.
6. Turn ignition off. Disconnect ignition switch connector C1. Turn ignition on. Observe KEY-IN-IGNITION input on BCM data list. If scan tool displays YES, go to next step. If scan tool does not display YES, go to step 9.
7. Turn ignition off. Disconnect ignition switch connector C2. Ensure BCM connector C3 is disconnected. Check continuity between BCM harness connector C3 terminal B12 (Light Green wire) and ground. If continuity does not exist, go to next step. If continuity exists, repair short to ground on Light Green wire. Go to step 12.
8. Check for poor connections at BCM connector. If connector is okay, go to step 10. If any problem is found, repair as necessary and go to step 12.
9. Check for poor connections at ignition switch connector. If connector is okay, go to step 11. If any problem is found, repair as necessary and go to step 12.
10. Replace BCM. See «BODY CONTROL MODULE»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) under REMOVAL & INSTALLATION. Program BCM. See «PROGRAMMING»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules). After repairs, go to step 12.
11. Replace ignition switch. See appropriate STEERING COLUMN SWITCHES article. After repairs, go to next step.
12. Using scan tool, clear DTCs. Turn ignition off and on. Wait 20 seconds, and retrieve DTCs. If DTC B2965 resets, go to step 2. If DTC does not reset, system is okay at this time.

If DTC is history, problem may be intermittent. Perform test procedure while wiggling wiring and connectors. Visually inspect connectors and circuits.

Serial data circuit is used to communicate information and commands between modules. When a module receives a message for a critical operating parameter, the module records the Body Control Module (BCM) number of the module which sent the message for State Of Health (SOH) monitoring.

When a module does not associate an identification number with at least one critical parameter within about 5 seconds after beginning communication, DTC will set. When more than one critical parameter does not have an identification number associated with it, DTC will only be reported once. When DTC is present, SERVICE VEHICLE SOON indicator will turn on and module will use a default value for the missing critical parameter.

1. If any history DTCs in the range of U1001-U1199 exist, perform appropriate diagnostic and repair procedure. See «BODY CONTROL MODULE DIAGNOSTIC TROUBLE CODE INDEX»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) table under SELF-DIAGNOSTIC SYSTEM. If no history DTCs within this range are set, go to next step.
2. Turn ignition on. Using scan tool, communicate with each module along the class 2 serial data line. Compare modules communicating with scan tool to actual modules along class 2 serial data line. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. If any modules are not communicating, go to next step. If all modules are communicating, go to step 11 .
3. Check power circuit of non-communicating module for open or short to ground conditions. See POWER DISTRIBUTION article in WIRING DIAGRAMS. If faulty circuit is found, repair as necessary and go to step 9 . If power circuit is okay, go to next step.
4. Turn ignition off. Check ground circuit for non-communicating module for open condition. See GROUND DISTRIBUTION article in WIRING DIAGRAMS. If faulty circuit is found, repair as necessary and go to step 9 . If circuit is okay, go to next step.
5. Check for poor connections at power, ground and class 2 circuits at non-communicating module connector. If faulty connection is found, repair as necessary and go to step 7 . If connections are okay, go to next step.
6. Replace non-communicating module. See appropriate procedure under «REMOVAL & INSTALLATION»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__removal-installation) . After repairs, go to step 9 .
7. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Select DISPLAY DTCs function for non-communicating module. If any DTCs that do not begin with "U" are present, perform appropriate diagnostic system check. See appropriate diagnostic system check in appropriate article for module that is not communicating. If no DTCs that do not begin with "U" are present, go to next step.
8. Using scan tool, clear DTCs. Go to next step.
9. Using scan tool, select DISPLAY DTCs function for non-communicating module that had DTC U1000 or U1255 set as current. If any DTCs that do not begin with "U" are present, perform appropriate diagnostic system check. See appropriate diagnostic system check in appropriate article for module that had a current DTC U1000 or U1255. If no DTCs that do not begin with "U" are present, go to next step.
10. Using scan tool, clear DTCs. System is okay at this time.
11. Display DTCs for module that had a current DTC U1000 or U1255. If any other DTCs were present, perform appropriate diagnostic system check. See appropriate diagnostic system check in appropriate article for module that had a current DTC U1000 or U1255. If no other DTCs were present, go to next step.
12. Using scan tool, clear DTCs, Turn ignition off and wait at least 5 seconds. Turn ignition on. Select DISPLAY DTCs function. If DTC U1000 or U1255 is set as current, go to next step. If DTC U1000 or U1255 is not set as current, go to «DIAGNOSTIC AIDS»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules) .
13. Replace non-communicating module that had DTC U1000 or U1255 set as current. See appropriate procedure under «REMOVAL & INSTALLATION»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__removal-installation) .

When a malfunction (such as a blown fuse to a module) occurs while modules are communicating, a loss of communication DTC is set as current. When modules stop communicating (ignition is turned off), the current loss of communication DTC is cleared, but the history DTC remains. When modules begin to communicate again, other modules will set a current loss of communication DTC.

Serial data circuit is used to communicate information and commands between modules. When a module receives a message for a critical operating parameter (node alive message), the module records the identification number of the module which sent the message for State Of Health (SOH) monitoring. Once an identification number is learned by a module, it will monitor for that module's node alive message. Each module on serial data circuit is required to send a node alive message every 2 seconds. When no message is detected from a learned identification number for 10 seconds, DTC U1XXX (XXX is equal to the 3-digit identification number) will set. Use MODULE IDENTIFICATION NUMBER table to determine which system is not communicating. For example, if DTC U1016 is set, Powertrain Control Module (PCM) is not communicating. A module with a class 2 serial data circuit malfunction or which loses power during a current ignition cycle will have a loss of communication DTC set by other modules that depend on information from that failed module. The modules that can communicate will set a DTC indicating the module can not communicate.

Current DTC will clear when node alive message from the failed identification number is detected on class 2 serial data line or at the end of the current ignition cycle. History DTC can only be cleared using scan tool. If more than one loss of communication DTC is set in either one or multiple modules, perform diagnosis in the following order

1. Current DTCs before history DTCs, unless otherwise indicated in testing procedure.
2. DTC which is reported the most times.
3. From lowest number DTC to highest number DTC.

MODULE IDENTIFICATION NUMBER

1. Check for open in battery supply voltage circuit to module identified as not communicating. See POWER DISTRIBUTION article in WIRING DIAGRAMS. If battery supply voltage is present, go to next step. If battery supply voltage is not present, repair as necessary and go to step 6 .
2. Ignition off. Check for open in ground circuit to module identified as not communicating. See GROUND DISTRIBUTION article in WIRING DIAGRAMS. If ground circuit is okay, go to next step. If ground circuit is open, repair as necessary and go to step 6 .
3. Check for poor connections at battery supply, ground and serial data line terminals for module identified as not communicating. If connections are okay, go to next step. If faulty connections are found, repair as necessary and go to step 6 .
4. Check for open or short in class 2 serial data circuit for module that is not communicating. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step 6 .
5. Replace module that is not communicating. See appropriate procedure under «REMOVAL & INSTALLATION»(/chevrolet/cavalier/iii-1995-2005/remont/body-cab-control-systems/#body-control-modules__removal-installation) . Go to next step.
6. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Display DTCs for module identified as not communicating. If scan tool displays any DTCs that do not begin with a "U", perform appropriate diagnostic system check. See appropriate diagnostic system check in appropriate article for module identified as not communicating. If scan tool does not display any DTCs that do not begin with a "U", go to next step.
7. Use scan tool to clear DTCs. Go to next step.
8. Display DTCs for module that had a loss of communication DTC. If scan tool displays any DTCs that do not begin with a "U", perform appropriate diagnostic system check. See appropriate diagnostic system check in appropriate article for module that had a loss of communication DTC. If scan tool does not display any DTCs that do not begin with a "U", go to next step.
9. Use scan tool to clear DTCs. Continue diagnosing or clearing DTCs until all modules with stored DTCs are repaired. Test is complete.

When multiple loss of communication DTCs are set concurrently, a likely cause is 2 opens in the serial data circuit. See DATA LINK CONNECTORS article in WIRING DIAGRAMS.

Serial data circuit is used to communicate information and commands between modules. In addition, node alive (state of health) messages are transmitted by each module on the serial data circuit about once every 2 seconds. When a module detects no messages and a low voltage on the serial data circuit for about 4 seconds, DTC U1300 is set, the setting of all other class 2 serial communication DTCs is inhibited and the module uses default values for all parameters received on the class 2 serial data circuit.

A current DTC U1300 will clear when a valid class 2 message is detected on serial data circuit or at the end of the current ignition cycle. A history DTC U1300 can only be cleared using scan tool.

DTC U1300 cannot be retrieved as current. Diagnosis for current DTC U1300 is accomplished using SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SELF-DIAGNOSTIC SYSTEM. An intermittent condition can be caused by short to ground on the class 2 serial data circuit.

Serial data circuit is used to communicate information and commands between modules. In addition, node alive (state of health) messages are transmitted by each module on the serial data circuit about once every 2 seconds. When a module detects no messages and a high voltage on the serial data circuit for about 4 seconds, DTC U1301 is set, the setting of all other class 2 serial communication DTCs is inhibited and the module uses default values for all parameters received on the class 2 serial data circuit.

A current DTC U1301 will clear when a valid class 2 message is detected on serial data circuit or at the end of the current ignition cycle. A history DTC U1301 can only be cleared using scan tool.

DTC U1301 cannot be retrieved as a current DLC. Diagnosis for current DTC U1301 is accomplished using SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SELF-DIAGNOSTIC SYSTEM. An intermittent condition can be caused by short to voltage on the class 2 serial data circuit.

REMOVAL & INSTALLATION

Disconnect negative battery cable. Disconnect harness connectors and remove Body Control Module (BCM) from bracket, located under left side of instrument panel. To install, reverse removal procedure. Program new module. See BCM PROGRAMMING/REGULAR PRODUCTION OPTION CODES under PROGRAMMING.

ELECTRONIC BRAKE CONTROL MODULE (EBCM)

Note. Electronic Brake Control Module (EBCM) is part of ABS unit, located near master cylinder.

1. Disconnect Electronic Brake Control Module (EBCM) harness connector. Disconnect EBCM harness from bracket. Remove EBCM mounting screws. Remove EBCM.
2. Clean mounting surfaces. To install, reverse removal procedure. Tighten EBCM mounting bolts to 44 INCH lbs. (5 N.m). Perform ABS diagnostic system check. See appropriate ANTI-LOCK article in BRAKES.

Removal & Installation (Cavalier)

1. Disconnect negative battery cable. Disable air bag system. See appropriate AIR BAG RESTRAINT SYSTEMS article. Remove defroster grill. Remove end caps. Open glove box. Remove trim pad screws. Remove trim pad. Remove instrument panel accessory trim plate screws. Unsnap and remove instrument panel accessory trim plate. Disconnect accessory trim plate harness connectors. Remove instrument panel cluster screws. Disconnect harness connector. Remove instrument panel cluster.
2. To install, reverse removal procedure. Reprogram instrument panel cluster. See appropriate ANALOG INSTRUMENT PANELS article. Enable air bag system. See appropriate AIR BAG RESTRAINT SYSTEMS article.

Removal & Installation (Grand Am)

1. Disconnect negative battery cable. Disable air bag system. See appropriate AIR BAG RESTRAINT SYSTEMS article. Remove defroster grill. Pull front trim plate up and remove. Remove end caps. Remove screws from glove box and center trim plates. Remove center trim plate. Remove trim pad screws and trim pad. Remove instrument panel cluster screws. Disconnect harness connector. Remove instrument panel cluster.
2. To install, reverse removal procedure. Reprogram instrument panel cluster. See appropriate ANALOG INSTRUMENT PANELS article. Enable air bag system. See appropriate AIR BAG RESTRAINT SYSTEMS article.

1. Turn ignition off and wait at least 10 seconds. Disconnect negative battery cable. Raise and support vehicle. Remove right side splash shield. Remove horn. Disconnect Powertrain Control Module (PCM) harness connectors. Remove PCM bolts. Slide PCM out of bracket.
2. To install, ensure service number on new PCM is the same as service number on old PCM (or updated number). To complete installation, reverse removal procedure. Tighten PCM harness connector screws to 71 INCH lbs. (8 N.m). Connect negative battery cable. Reprogram PCM. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION.

1. Disable air bag system. See appropriate AIR BAG RESTRAINT SYSTEMS article. Remove passenger's front seat. Remove kick panel/sill plate. Lift carpet and insulation. Remove CPA clip and disconnect SDM harness connector. Remove Sensing and Diagnostic Module (SDM) mounting bolts. Remove SDM from vehicle. (Scheme 4)
2. To install, reverse removal procedure. Tighten SDM bolts to 10 ft. lbs. (14 N.m). Ensure arrow on module is pointing toward front of vehicle. Activate air bag system. See appropriate AIR BAG RESTRAINT SYSTEMS article.

Scheme 4

Body Control Module Wiring Diagrams (Cavalier & Sunfire). Scheme 5

See also:
• PASSWORD LEARN PROCEDURE
• BODY CONTROL SYSTEM DIAGNOSTIC TROUBLE CODE INDEX
• SCAN TOOL DOES NOT POWER UP
• BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK
• ELECTRONIC BRAKE CONTROL MODULE (EBCM)
• BCM PROGRAMMING/REGULAR PRODUCTION OPTION CODES
• DIAGNOSTIC AIDS
• REMOVAL & INSTALLATION