Body Control Modules: Diagnosis Chevrolet Venture I

PRELIMINARY INSPECTION

Before performing tests, check the following instrument panel fuse block fuses: BCM PRGRM (10-amp) fuse, CIGAR/DLC (15-amp) fuse, CTSY LAMP (10-amp) fuse, IGN 1 (10-amp) fuse, MALL/PRGM (10-amp) fuse, PASS KEY (10-amp) fuse, PCM ABS (10-amp) fuse, PCM CRANK (10-amp) fuse, PCM/PASSKEY/CLUSTER (10-amp) fuse, PWR LOCK (20-amp) fuse, RAP RELAY (10-amp) fuse and SIR (15-amp) fuse.

Check the following underhood accessory junction block fuses: ECM SENSE (10-amp) fuse, HORN (15-amp) fuse, IGN 1 U/H (15-amp) fuse, PARK LP (20-amp) fuse and RADIO (10-amp) fuse.

Check system ground circuits. See appropriate wiring diagram in GROUND DISTRIBUTION article under WIRING DIAGRAMS. Check for proper operation of parking lights. If parking lights do not operate properly, repair parking lights as necessary. See appropriate wiring diagram in EXTERIOR LIGHTS article under WIRING DIAGRAMS.

Check for proper operation of automatic power door locks. If door locks do not operate properly, repair power door lock system as necessary. See POWER DOOR LOCKS - MONTANA, SILHOUETTE & VENTURE article. Check for proper operation of power sliding side doors. If power sliding side doors do not operate properly, repair power sliding side door as necessary. See POWER SLIDING SIDE DOORS - MONTANA, SILHOUETTE & VENTURE article. Check for proper operation of Remote Keyless Entry (RKE) system. If RKE system does not operate properly, repair RKE system as necessary. See REMOTE KEYLESS ENTRY SYSTEMS - MONTANA, SILHOUETTE & VENTURE article. Check for proper operation of horn system. If horn does not operate properly, repair horn system as necessary. See STEERING COLUMN SWITCHES - TRUCKS - EXCEPT TRACKER article.

Always check harness connectors for good terminal contact before replacing any component. Inspect for proper installation and operation of any aftermarket electronic equipment which may affect operations other systems.

BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK

1. Perform on-board diagnostics. See «ON-BOARD DIAGNOSTICS»(ref-9085-S27555392872000100700000) under SELF-DIAGNOSTIC SYSTEM. If BCM enters on-board diagnostic mode, go to next step. If BCM on-board diagnostic mode can not be entered, see «BODY CONTROL MODULE INOPERATIVE»(ref-9085-S28663739742000100900000) under SYSTEM TESTS.
2. Read on-board Diagnostic Trouble Codes (DTC). If any DTC exists, go to appropriate procedure for BCM DTC present. See «BCM DTC INDEX»(ref-9085-S07963480232000100900000) table under SELF-DIAGNOSTIC SYSTEM. If no BCM DTC is present, repair concern by symptoms present. See «SYSTEM TESTS»(ref-9085-S16865426212000100500000) .

LIGHTING SYSTEM DIAGNOSTIC SYSTEM CHECK

1. Attempt to operate power door locks from door lock/unlock switch. If power door locks operate, go to next step. If power door locks do not operate, diagnose concern with power door lock system. See «POWER DOOR LOCKS - MONTANA, SILHOUETTE & VENTURE»(ref-8382) article.
2. Perform on-board diagnostic check for Body Control Module (BCM) Diagnostic Trouble Codes (DTC). If BCM DTC 2 is stored, go to «DTC 2: BATTERY FEED TO COURTESY LIGHTS»(ref-9085-S13878747592000101200000) . If BCM DTC 2 is not stored, go to next step.
3. If BCM DTC 3 is stored, go to «DTC 3: COURTESY LIGHTS»(ref-9085-S39194417562000101200000) . If BCM DTC 3 is not stored, go to next step.
4. If any other BCM DTCs are stored, go to appropriate procedure for BCM DTC present. See «BCM DTC INDEX»(ref-9085-S07963480232000100900000) table under SELF-DIAGNOSTIC SYSTEM. If no BCM DTCs are present, diagnose concerns by symptoms present. See appropriate wiring diagram under «ILLUMINATION/INTERIOR LIGHTS»(ref-8788) article.

RETAINED ACCESSORY POWER (RAP) 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»(ref-9085-S03420620282000100700000) under SYSTEM TESTS.
2. Turn ignition switch to RUN position. Using scan tool, attempt to establish communication with radio. If scan tool communicates with radio, go to next step. If scan tool does not communicate with radio, go to «SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE»(ref-9085-S24676683282000100700000) under SYSTEM TESTS.
3. If any loss of communication DTCs exist (any DTC beginning with a "U"), go to «SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE»(ref-9085-S24676683282000100700000) under SYSTEM TESTS. If no loss of communication DTCs exist, go to next step.
4. Enter BCM diagnostic mode. See «ON-BOARD DIAGNOSTICS»(ref-9085-S27555392872000100700000) under SELF-DIAGNOSTIC SYSTEM. If BCM enters into diagnostic mode, diagnose by symptoms or BCM DTCs present. If BCM does not enter diagnostic mode, go to «BODY CONTROL MODULE INOPERATIVE»(ref-9085-S28663739742000100900000) under SYSTEM TESTS.

ANTI-THEFT SYSTEM DIAGNOSTIC SYSTEM CHECK

See CONTENT THEFT DETERRENT SYSTEM OPERATION CHECK in ANTI-THEFT SYSTEMS - MONTANA, SILHOUETTE & VENTURE article.

DRIVER INFORMATION SYSTEM DIAGNOSTIC SYSTEM CHECK

See DRIVER INFORMATION SYSTEM DIAGNOSTIC SYSTEM CHECK in ANALOG INSTRUMENT PANELS - MONTANA, SILHOUETTE & VENTURE article.

INSTRUMENT PANEL CLUSTER DIAGNOSTIC SYSTEM CHECK

See INSTRUMENT PANEL DIAGNOSTIC SYSTEM CHECK in ANALOG INSTRUMENT PANELS - MONTANA, SILHOUETTE & VENTURE article.

POWER SLIDING SIDE DOORS DIAGNOSTIC SYSTEM CHECK

See SELF-DIAGNOSTIC SYSTEM in POWER SLIDING SIDE DOORS - MONTANA, SILHOUETTE & VENTURE article.

Entering Input Diagnostic Modes

After displaying and reading all BCM DTCs stored in memory, BCM will enter input/output diagnostic mode. Input diagnostic mode will identify BCM is receiving input information from switches or systems. BCM may flash fasten seat belts warning indicator once and/or chime tone will sound once, when any of following inputs are activated

1. Courtesy Lighting Switches
2. Door Lock Cylinder Switches
3. Door & Liftgate Ajar Switches
4. Driver Fasten Seat Belt Switch
5. Driver Information Display (DID)
6. Glove Box Light Switch
7. Hazard Switch
8. Headlight Switch
9. Power Door Lock Switches
10. Shock Sensor
11. Power Sliding Side Door Ajar Switches
12. Sunshade Illuminated Vanity Mirrors
13. Remote Keyless Entry (RKE) Transmitter Requests

Output Diagnostic Modes

After displaying and reading all BCM DTCs stored in memory, BCM will enter input/output diagnostic mode. To test BCM output modes, cycle interior light override switch to ON, then OFF positions. See COMPONENT LOCATIONS . BCM will enter output diagnostic test Mode 1. Each cycling of interior lighting override switch ON/OFF will enter next output test mode available, depending upon vehicle options and BCM type. Courtesy lighting must be enabled during this procedure. When checking courtesy lighting functions, ensure Instrument Panel (I/P) dimmer switch is in any position except off or DOME. Ensure interior light override switch is on (courtesy lighting is enabled). When BCM completes cycle through all output test modes available, sequence will be repeated. Modes 1-3 are available on models with BCM type 2 or 3, Modes 1-7 are available on models with BCM type 4. Ensure all output modes operate designated features described. Diagnostic output modes are as follows

1. Mode 1 De-activates courtesy light output and removes power to all interior lights.
2. Mode 2 Activates courtesy light output and provides power to all interior lights (courtesy lighting must be enabled; interior light override switch in ON position).
3. Mode 3 Activates courtesy lights output and turns ON all of courtesy lights (courtesy lighting must be enabled; interior light override switch must be ON).
4. Mode 4 Activates theft deterrent relay for one second and turns ON the headlights (BCM type 4).
5. Mode 5 Energizes horn relay for 25 ms (BCM type 4).
6. Mode 6 Turns on SECURITY warning LED indicator (BCM type 4).
7. Mode 7 Turns off SECURITY warning LED indicator (BCM type 4)

Exiting On-Board Diagnostics

To exit BCM diagnostics mode and return to normal operation, turn ignition switch to LOCK position. Install BCM PRGRM (10-amp) fuse. Turn ignition switch to ON position. System will exit on-board diagnostics.

SCAN TOOL DIAGNOSTICS

Note. Body Control Modules (BCM) has on-board diagnostics capabilities. When diagnosing BCM concerns, go to ON-BOARD DIAGNOSTICS .

Control modules connected to class 2 data bus can detect system malfunctions or abnormalities and set Diagnostic Trouble Codes (DTCs). When a malfunction occurs, a current DTC will be stored in the related control modules. See BODY CONTROL MODULE (BCM) DTC DEFINITIONS table. Current DTCs indicate a control module has detected a fault or malfunction which is present during an ignition cycle. A history DTC indicates that a module has previously detected a current malfunction that is not present or no longer exists. Scan tool diagnostics should be used when checking for class 2 data bus circuit loss of communications codes (U1XXX), non-BCM related DTCs, and clearing most all stored DTCs (except BCM DTCs).

BODY CONTROL MODULE (BCM) DTC DEFINITIONS

DIAGNOSTIC TESTS

Note. For BCM DTCs retrieved using on-board diagnostics, see BCM DTC INDEX table under in SELF-DIAGNOSTIC SYSTEM.

Note. For DTCs retrieved using scan tool, go to BODY CONTROL MODULE (BCM) DTC DEFINITIONS table.

Circuit Description

Body Control Module (BCM) controls operation of fasten seat belt warning indicator in the instrument cluster to remind driver to fasten seat belt. With ignition switch turned to ON position, fasten seat belt warning indicator will illuminate for 55 seconds, or until driver fastens seat belt buckle. If seat belt is removed during an ignition cycle or while driving, fasten seat belt warning indicator will illuminate again for 55 seconds. Fasten seat belt warning indicator will not illuminate when fasten seat belt indicator control circuit is shorted to ground. Fasten seat belt warning indicator will remain illuminated when indicator control circuit is shorted to voltage.

Scheme 3

Scheme 4

1. Perform lighting system diagnostic system check. See «LIGHTING SYSTEM DIAGNOSTIC SYSTEM CHECK»(ref-9085-S14491917712000101300000) under TROUBLE SHOOTING. Go to next step.
2. Turn ignition switch to ON position while monitoring seat belt indicator. If seat belt indicator remains illuminated continuously, go to next step. If seat belt indicator does remain illuminated, go to step 8.
3. Turn ignition switch to LOCK position. Disconnect BCM connector C2. (Scheme 3) Turn ignition switch to ON position. If seat belt indicator remains illuminated continuously, go to step 5. If seat belt indicator does not remains illuminated continuously, go to next step.
4. Replace Body Control Module (BCM). See «BODY CONTROL MODULE»(ref-9085-S05004352692000101300000) under REMOVAL & INSTALLATION. If vehicle is equipped with factory installed Central Theft Deterrent (CTD) anti-theft system, perform CTD relearn procedure. See «CENTRAL THEFT DETERRENT (CTD) RELEARN»(ref-9085-S20875384942000101200000) under PROGRAMMING. Program feature customization settings. See «ENTER FEATURE CUSTOMIZATION MODE»(ref-9085-S41705672152000100900000) under PROGRAMMING. After repair is complete, go to step 10.
5. Disconnect IPC connector C1. (Scheme 3)and (Scheme 4). Using a DVOM, measure voltage of seat belt supply circuit (Dark Green/White wire) between BCM connector C2 terminal D12 and Instrument Panel Cluster (IPC) connector C1 terminal "E". If reading is less than one volt, go to next step. If reading is one volt or more, go to step 7.
6. Replace IPC. Perform appropriate set up procedure for replacement IPC. See «ANALOG INSTRUMENT PANELS - MONTANA, SILHOUETTE & VENTURE»(ref-8849) article. Contact an authorized A/C Delco service center for transfer of information from failed Instrument Panel Cluster (IPC) or affix appropriate label with necessary vehicle information on driver door pillar. Recheck system operation, go to step 10.
7. Locate and repair short to voltage in seat belt supply circuit (Dark Green/White wire) between BCM connector C2 terminal D12 and IPC connector C1 terminal "E". (Scheme 3)and (Scheme 4). Check system operation, go to step 10.
8. Disconnect BCM connector C2. Disconnect IPC connector C1. Using DVOM, measure resistance between ground and seat belt supply circuit at BCM connector C2 terminal D12 (Dark Green/White wire). Measure resistance of Dark Green/White wire between IPC connector C1 terminal "E" and BCM connector C2 terminal D12. (Scheme 3)and (Scheme 4).
9. Locate and repair short to ground in seat belt supply circuit (Dark Green/White wire) between BCM connector C2 terminal D12 and IPC connector C1 terminal "E". (Scheme 3)and (Scheme 4). Recheck system operation, go to next step.
10. Clear BCM DTCs. See «ON-BOARD DIAGNOSTICS»(ref-9085-S27555392872000100700000) in SELF-DIAGNOSTIC SYSTEM. Operate vehicle in attempt to reset DTC. Check for DTCs. If DTC 3 resets, go to step 2. If DTC does not remain, system is okay.

Body Control Module (BCM) controls inadvertent battery load rundown protection feature. DTC sets when BCM detects a short to power or ground in courtesy lighting circuit 1393 (Dark Blue wire) between BCM, interior lights, multifunction switch, and/or detects a short to power or ground in circuit 328 (Purple wire) between interior light switch and interior lighting. When DTC 2 is set, rundown feature is disabled if circuit is shorted to power. If shorted to ground, interior lighting will be disabled.

1. Perform diagnostic system check of Body Control Module (BCM). See «BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK»(ref-9085-S24885270842000100900000) under TROUBLE SHOOTING. Go to next step.
2. Ensure Instrument Panel (I/P) dimmer switch located below headlight switch is turned off. Disconnect BCM connector C1. Turn interior lighting override switch located in overhead console is turned off (courtesy lighting is disabled). Connect test light between BCM connector C1 terminals "G" and "E". If test light illuminates, go to next step. If test light does not illuminate, go to step 4 .
3. Repair short to ground in circuit 1393 (Dark Blue wire). See appropriate wiring diagram in «ILLUMINATION/INTERIOR LIGHTS»(ref-8788) article. After repair is complete, go to step 11 .
4. Leaving test light connected, turn interior lighting override switch on. If test light illuminates, go to next step. If test light does not illuminate, go to step 6 .
5. Repair short to ground in circuit 328 (Purple wire) between interior lighting override switch and most all interior lighting. See appropriate wiring diagram in «ILLUMINATION/INTERIOR LIGHTS»(ref-8788) article. After repair is complete, go to step 11 .
6. Disconnect test light. Turn ignition switch to ON position. Turn interior lighting override switch off. Turn on any of the following lights: glove box, left front roof rail reading light, left rear roof rail reading light, left or right sunshade vanity mirror light, or right rear roof rail reading light. If any of the lights illuminate, go to next step. If all lights do not illuminate, go to step 8 .
7. Repair short to voltage in circuit 328 (Purple wire) between interior lighting override switch and most all interior lighting. See appropriate wiring diagram in «ILLUMINATION/INTERIOR LIGHTS»(ref-8788) article. After repair is complete, go to step 11 .
8. Turn instrument panel dimmer switch on. If glove box light, left front roof rail reading light, left rear roof rail reading light, left or right sunshade vanity mirror light or right rear roof rail reading light illuminate, go to next step. If all of the lights listed do not illuminate, go to step 10 .
9. Repair short to voltage in circuit 1393 (Dark Blue wire) between interior lighting override switch and Body Control Module (BCM). See appropriate wiring diagram in «ILLUMINATION/INTERIOR LIGHTS»(ref-8788) article. After repair is complete, go to step 11 .
10. Replace Body Control Module (BCM). See «BODY CONTROL MODULE»(ref-9085-S05004352692000101300000) under REMOVAL & INSTALLATION. If vehicle is equipped with factory installed Central Theft Deterrent (CTD) anti-theft system, perform CTD relearn procedure. See «CENTRAL THEFT DETERRENT (CTD) RELEARN»(ref-9085-S20875384942000101200000) under PROGRAMMING. Program feature customization settings. See «ENTER FEATURE CUSTOMIZATION MODE»(ref-9085-S41705672152000100900000) under PROGRAMMING. After repair is complete, go to next step.
11. Turn ignition switch to LOCK position. Restore all disconnected connectors and components. Open any vehicle door for 10 seconds. Close all vehicle doors. Remove BCM PRGRM (10-amp) fuse. Turn ignition switch to ACC position and count chime tones to identify BCM type. Within one second, cycle ignition switch from ACC position to LOCK position, then back to ACC position. Count chime tones for any BCM DTCs stored. If any BCM DTCs exist, go to appropriate procedure for BCM DTCs stored. If no chime tones are heard, no BCM DTCs are present and system is okay. Program feature customization settings.

Body Control Module (BCM) controls power supply for interior light illumination. BCM will turn on interior lights when any of the following actions occur: When any door is opened. Instrument panel dimmer switch is turned to DOME position. Exit illumination is activated. Doors are unlocked using Remote Keyless Entry (RKE) transmitter (on models with type 3 or 4 BCM). Doors are unlocked using door key cylinder (on models with type 4 BCM). BCM turns off interior lighting when all doors are closed or when interior lighting override switch is turned off. DTC 3 will be set when BCM senses a short to positive battery in interior light control circuit 690 (Gray/Black wire) between BCM and all courtesy lights. To change interior lighting settings, see INTERIOR LIGHTING MODES under PROGRAMMING.

1. Perform diagnostic system check of Body Control Module (BCM). See «BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK»(ref-9085-S24885270842000100900000) under TROUBLE SHOOTING. Go to next step.
2. Ensure all interior lights are off. Disconnect BCM connector terminal No. C1. Using a DVOM, measure voltage between ground and BCM connector terminal "F". Turn ignition switch to ON position. If battery voltage is present, go to next step. If battery voltage is not present, go to step 4 .
3. Repair short to battery positive voltage in circuit 690 (Gray/Black wire) as necessary. Go to step 5 .
4. Replace Body Control Module (BCM). See «BODY CONTROL MODULE»(ref-9085-S05004352692000101300000) under REMOVAL & INSTALLATION. If vehicle is equipped with factory installed Central Theft Deterrent (CTD) anti-theft system, perform CTD relearn procedure. See «CENTRAL THEFT DETERRENT (CTD) RELEARN»(ref-9085-S20875384942000101200000) under PROGRAMMING. Program feature customization settings. See «ENTER FEATURE CUSTOMIZATION MODE»(ref-9085-S41705672152000100900000) under PROGRAMMING. After repair is complete, go to next step.
5. Turn ignition switch to LOCK position. Restore all disconnected connectors and components. Open any vehicle door for 10 seconds. Close all vehicle doors. Remove BCM PRGRM (10-amp) fuse. Turn ignition switch to ACC position and count chime tones to identify BCM type. Within one second, cycle ignition switch from ACC position to LOCK position, then back to ACC position. Count chime tones for any BCM DTCs stored. If any BCM DTCs exist, go to appropriate procedure for BCM DTCs stored. If no chime tones are heard, no BCM DTCs are present and system is okay.

Body Control Module (BCM) controls headlights and horn operation when Central Theft Deterrent (CTD) feature is in armed or warning modes, if theft attempt is detected, Remote Keyless Entry (RKE) transmitter PANIC button is pressed or when theft deterrent system is in trunk open mode. BCM sets a DTC 6 when BCM detects a short to ground or short to voltage in circuit 301 (Brown/White wire) between BCM and theft deterrent relay located in relay center. When DTC 6 is set, BCM will not turn on headlights when armed, warning, alarm or trunk open modes are requested. If circuit 301 (Brown/White wire) is shorted to ground, headlights will remain illuminated. BCM DTC 6 will clear when short to ground or short to voltage is no longer present. When BCM DTC 6 is current, check for short to ground or short to voltage in circuit 301 (Brown/white wire). Check for faulty theft deterrent relay. Check for an intermittent condition in related wiring harnesses and connectors.

1. Perform diagnostic system check of Body Control Module (BCM). See «BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK»(ref-9085-S24885270842000100900000) under TROUBLE SHOOTING. Go to next step.
2. Turn ignition switch to LOCK position. Disconnect theft deterrent relay located in relay center. Relay center is mounted to bracket on right side of instrument panel next to BCM. Disconnect BCM connector C2. Turn ignition switch to ON position. Using a DVOM, measure voltage between ground and BCM connector C2 terminal No. 11 (Brown/White wire). If reading is less than 2 volts, go to next step. If reading is 2 volts or more, go to step 4 .
3. Using a DVOM, measure resistance between ground and BCM connector C2 terminal No. 11 (Brown/White wire). If reading is infinite, go to next step. If reading does not indicate infinite resistance, go to step 6 .
4. Measure resistance between coil side terminals of theft deterrent relay. If reading is 65-110 ohms, go to step 8 . If reading is not between 65-110 ohms, go to step 7 .
5. Repair short to positive battery voltage in Brown/White wire between theft deterrent relay and BCM connector C2 terminal No. 11. Go to step 9 .
6. Repair short to ground in Brown/White wire between theft deterrent relay and BCM connector C2 terminal No. 11. Go to step 9 .
7. Replace theft deterrent relay. Retest system for normal operation. Go to step 9 .
8. Check BCM wiring harness and connector for good terminal contact. Repair connections as necessary. If connections are okay, verify which BCM is equipped on vehicle. See «BCM TYPE VERIFICATION»(ref-9085-S14984023642000100500000) under SELF-DIAGNOSTIC SYSTEM. Replace Body Control Module (BCM). See «BODY CONTROL MODULE»(ref-9085-S05004352692000101300000) under REMOVAL & INSTALLATION. If vehicle is equipped with factory installed Central Theft Deterrent (CTD) anti-theft system, perform CTD relearn procedure. See «CENTRAL THEFT DETERRENT (CTD) RELEARN»(ref-9085-S20875384942000101200000) under PROGRAMMING. Program feature customization settings. See «ENTER FEATURE CUSTOMIZATION MODE»(ref-9085-S41705672152000100900000) under PROGRAMMING.
9. Turn ignition switch to LOCK position. Restore any previously disconnected connectors or components. Remove BCM PRGRM (10-amp) fuse from instrument panel fuse block. Turn ignition switch to ON position. Verify proper type of BCM is installed by counting number of chime tones. See «BCM TYPE VERIFICATION»(ref-9085-S14984023642000100500000) under SELF-DIAGNOSTIC SYSTEM. If proper BCM for vehicle is installed, go to next step. If incorrect BCM is installed, replace BCM. Go to step 8 , then repeat this step.
10. Clear BCM DTCs. See «ON-BOARD DIAGNOSTICS»(ref-9085-S27555392872000100700000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle in attempt to reset DTC. Go to next step.
11. Within one second, cycle ignition switch to ACC to OFF position, then to ACC position. Chime will sound indicating DTC number from lowest (pause between DTCs) to highest procedure for DTC. If BCM DTCs exist, go to appropriate test procedure for DTCs. If chime does not sound, repair is complete, system okay.

BCM sets a DTC 7 when BCM detects a short to ground or short to voltage in horn relay coil circuit 28 (Black wire) between horn relay and BCM. Horns are activated when ground is applied to horn relay coil through circuit 28 (Black wire) between Body Control Module (BCM), horn switch in steering wheel and underhood junction block connector C2 terminal E7.

1. Ensure courtesy lights and power door locks are operational. Perform diagnostic system check of Body Control Module (BCM). See «BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK»(ref-9085-S24885270842000100900000) under TROUBLE SHOOTING. If BCM DTC 7 is present, go to next step.
2. Turn ignition switch to LOCK position. Disconnect horn relay. Disconnect BCM connector C2. Turn ignition switch to ON position. Using a test light connected to ground, check for battery voltage at BCM connector C2 terminal D10 (Black wire). (Scheme 3) If test light illuminates, go to step 4. If test light does not illuminate, go to next step.
3. Using a test light connected to positive battery, probe BCM connector C2 terminal D10 (Black wire). (Scheme 3) If test light illuminates, go to step 5. If test light does not illuminate, go to step 6.
4. Disable air bag system. See DISABLING & ACTIVATING AIR BAGS in «AIR BAG RESTRAINT SYSTEMS»(ref-97270) article. Repair short to voltage in circuit 28 (Black wire) between underhood junction block connector C2 terminal E7 and BCM harness connector terminal D10, or short to voltage in circuit 28 (Black wire) between underhood junction block connector C2 terminal E7 through steering column to horn switch in steering wheel. See appropriate wiring diagram in «STEERING COLUMN SWITCHES - TRUCKS - EXCEPT TRACKER»(ref-4432). After repairs, go to step 7.
5. Disable air bag system. See DISABLING & ACTIVATING AIR BAGS in «AIR BAG RESTRAINT SYSTEMS»(ref-97270) article. Repair short to ground in circuit 28 (Black wire) between underhood junction block connector C2 terminal E7 and BCM harness connector terminal D10, or short to ground in circuit 28 (Black wire) between underhood junction block connector C2 terminal E7 through steering column to horn switch in steering wheel. See appropriate wiring diagram in «STEERING COLUMN SWITCHES - TRUCKS - EXCEPT TRACKER»(ref-4432). After repairs, go to step 7.
6. Verify which BCM type vehicle is equipped with. See «BCM TYPE VERIFICATION»(ref-9085-S14984023642000100500000) under SELF-DIAGNOSTIC SYSTEM. Replace Body Control Module (BCM). See «BODY CONTROL MODULE»(ref-9085-S05004352692000101300000) under REMOVAL & INSTALLATION. If vehicle is equipped with factory installed Central Theft Deterrent (CTD) anti-theft system, perform CTD relearn procedure. See «CENTRAL THEFT DETERRENT (CTD) RELEARN»(ref-9085-S20875384942000101200000) under PROGRAMMING. Program feature customization settings. See «ENTER FEATURE CUSTOMIZATION MODE»(ref-9085-S41705672152000100900000) under PROGRAMMING.
7. Clear BCM DTCs. See «ON-BOARD DIAGNOSTICS»(ref-9085-S27555392872000100700000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle in attempt to reset DTC. If BCM DTCs reset, go to step 2. If BCM DTCs does not remain, system is okay.

Diagnostic Trouble Code (DTC) sets when Body Control Module (BCM) detects an open, short to ground or short to power in Remote Keyless Entry (RKE) class 2 serial data circuit (Black/White wire) between Remote Control Door Lock Receiver (RCDLR) and BCM.

Scheme 5

1. Ensure courtesy lights and power door locks are operational. Perform diagnostic system check of Body Control Module (BCM). See «BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK»(ref-9085-S24885270842000100900000) under TROUBLE SHOOTING. If BCM DTC 8 is present, go to next step.
2. Turn ignition switch to OFF position. Disconnect Remote Control Door Lock Receiver (RCDLR) connector. Turn ignition switch to ON position. Using DVOM, measure voltage between ground and RCDLR connector terminal "E" (Black/White wire). (Scheme 5) If voltage is near battery voltage, go to next step. If voltage is not near battery voltage, go to step 4.
3. Turn switch to OFF position. Connect a test light between RCDLR connector terminal "E" (Black/White wire) and ground. (Scheme 5) Turn ignition switch to ON position. If test light is on, go to step 8. If test light is not illuminated, go to step 6.
4. Test Black/White wire between RCDLR and BCM for high resistance or open. If problem was not found, go to next step. If problem was found, repair as necessary, and then go to step 11.
5. Test Black/White wire between RCDLR and BCM for short to ground. If problem was not found, go to step 7. If problem was found, repair as necessary, and then go to step 11.
6. Inspect for poor connections at RCDLR connector. (Scheme 5) If problem was not found, go to step 10. If problem was found, repair as necessary, and then go to step 11.
7. Inspect for poor connections at BCM connector. (Scheme 3) If problem was not found, go to step 9. If problem was found, repair as necessary, and then go to step 11.
8. Repair short to voltage in Black/White wire between RCDLR and BCM. Go to step 11.
9. Replace BCM. Replace Body Control Module (BCM). See «BODY CONTROL MODULE»(ref-9085-S05004352692000101300000) under REMOVAL & INSTALLATION. If vehicle is equipped with factory installed Central Theft Deterrent (CTD) anti-theft system, perform CTD relearn procedure. See «CENTRAL THEFT DETERRENT (CTD) RELEARN»(ref-9085-S20875384942000101200000) under PROGRAMMING. Program feature customization settings. See «ENTER FEATURE CUSTOMIZATION MODE»(ref-9085-S41705672152000100900000) under PROGRAMMING. After repair is complete, go to next step.
10. Replace RCDLR module. See REMOVAL & INSTALLATION in «REMOTE KEYLESS ENTRY SYSTEMS - MONTANA, SILHOUETTE & VENTURE»(ref-4696) article.
11. Clear BCM DTCs. See «ON-BOARD DIAGNOSTICS»(ref-9085-S27555392872000100700000) under SELF-DIAGNOSTIC SYSTEM. Operate system and ensure BCM DTCs do not reset.

Diagnostic Aids

DTCs U1000-U1255 is set when a malfunction (such as an open fuse to a module) occurs while modules are communicating, a Loss Of Communication DTCs set as a current code. When modules stop communicating (ignition is turned OFF) current Loss Of Communication DTC is cleared, but history DTC remains. When modules begin to communicate again, module with open fuse will not be learned by other modules. DTCs U1000-U1255 will set as a current code by other modules. If malfunction occurs when modules are not communicating, DTCs U1000-U1255 will be set.

Diagnostic Procedures

1. Connect scan tool to Data Link Connector (DLC). (Scheme 6) Using scan tool, check for any DTCs between DTC U1001 and DTC U1254 with a history status. If any DTCs between U1001 and U1254 are stored as history codes, go to «DTC U1001-U1254: LOSS OF COMMUNICATION WITH XXX»(ref-9085-S01181985012000101000000). If no DTCs between U1001-U1254 are stored as history codes, go to next step.
2. Turn ignition switch to ON position, leaving engine off. Attempt to communicate with each module on class 2 serial data circuit. (If using a Tech 2 scan tool, obtain this information using CLASS 2 MESSAGE MONITOR feature). Record all codes related to modules communications on class 2 serial data circuit. Compare list of modules which are communicating to list given. If any module(s) on class 2 serial data circuit do not communicate, go to next step. If module on class 2 serial data bus circuit are communicating, go to step 13
3. Using DVOM connected to ground, backprobe all power supply circuits of affected module(s) for battery voltage. See appropriate wiring diagram in «POWER DISTRIBUTION»(ref-8628) article in WIRING DIAGRAMS. If battery voltage is present at all power supply circuits of affected module, go to next step. If battery voltage is not present at any terminal of affected module, inspect power supply fuse for an open, and check for an open or short to ground in power supply circuit. After repairs are complete, go to step 9.
4. Turn ignition switch to LOCK position. Test all ground circuit(s) of affected control module for continuity to ground. See appropriate wiring diagram in «GROUND DISTRIBUTION»(ref-8627) article in WIRING DIAGRAMS. If continuity exists at all ground circuits of affected module, go to next step. If continuity does not exist for any circuit, locate and repair open in ground circuit. After repairs are complete, go to step 9.
5. Disconnect splice pack SP205 located behind driver's knee bolster. Inspect SP205 connector for poor connection. (Scheme 7) If connection is okay, go to next step. If poor connection exists, repair as necessary. After repairs are complete, go to step 9.
6. Check class 2 serial data circuit of affected module which is not communicating for an open. See appropriate wiring diagram in «DATA LINK CONNECTORS»(ref-8610) article in WIRING DIAGRAMS. If an open does not exist, go to next step. If an open exists, repair wiring as necessary. After repairs are complete, go to step 9.
7. Inspect for poor connections at related connectors for power supply circuit(s), ground circuit(s), and class 2 serial data circuit of affected control module which is not communicating. Repair faults as necessary. After repairs are complete, go to step 9. If all related connections are okay, go to next step.
8. Replace control module which is not communicating properly. Go to step 11.
9. Turn ignition switch to ON position. Using scan tool, select DISPLAY DTCs function for control module which was not communicating. If scan tool displays any DTCs, perform appropriate diagnostic system check for affected control module. See «TROUBLE SHOOTING»(ref-9085-S02717531962000100500000). If scan tool does not display any "U" type DTCs, go to next step.
10. Using scan tool, record and clear DTCs present. Go to next step.
11. Select DISPLAY DTCs function for control module which had U1000 or U1255 set as a current DTC. If scan tool display's any DTC which do not begin with a "U", perform appropriate diagnostic system check for affected control module. See «TROUBLE SHOOTING»(ref-9085-S02717531962000100500000). If scan tool displays any "U" type DTCs, go to next step.
12. Using scan tool, record and clear all DTCs. Repair is complete.
13. If any other DTCs were recorded for modules which had DTC U1000 or DTC U1255 set as current DTCs, perform appropriate system test for affected module(s). If no other current DTCs are stored for affected control modules exist, see diagnostic aids under description form this DTC.
14. Turn ignition switch to ON position. Using scan tool, record and clear DTCs. Turn ignition switch to OFF position, for at least 5 seconds. Turn ignition switch to ON position. Select DISPLAY DTCs function. If scan tool displays DTC U1000 or U1255 set as a current DTC, replace affected control module which stored DTCs U1000 or U1255 as a current DTC. If scan tool does not display DTCs U1000 or U1255, see diagnostic aids under description form this DTC.

Scheme 6

Scheme 7

When a malfunction (such as an open fuse to a module) occurs while modules are communicating, a "U" type of DTC is set as a current code. When modules stop communicating (ignition is turned OFF) current "U" type DTC changes to a history DTC. When modules begin to communicate again, module with poor connection, poor power supply, open fuse or other intermittent condition may not be learned by other class 2 data circuit control modules. DTCs U1000-U1255 will set as a current code by other control modules if malfunction occurs when modules are not communicating, DTCs U1000-U1255 is set.

1. Using DVOM connected to ground, backprobe all power supply circuits of affected module(s) for battery voltage. See appropriate wiring diagram in «POWER DISTRIBUTION»(ref-8628) article in WIRING DIAGRAMS. If battery voltage is present at all power supply circuits of affected module, go to next step. If battery voltage is not present at any terminal of affected module, inspect power supply fuse for an open fuse, and check for an open or short to ground in power supply circuit. After repairs are complete, go to step 9.
2. Turn ignition switch to LOCK position. Test all ground circuit(s) of affected control module for continuity to ground. See appropriate wiring diagram in «GROUND DISTRIBUTION»(ref-8627) article under WIRING DIAGRAMS. If continuity exists at all ground circuits of affected module, go to next step. If continuity does not exist for any circuit, locate and repair open in ground circuit. After repairs are complete, go to step 9.
3. Disconnect splice pack SP205 located behind driver's knee bolster. (Scheme 7) Inspect SP205 connector for poor connection. If connection is okay, go to next step. If poor connection exists, repair as necessary. After repairs are complete, go to step 9.
4. Check class 2 serial data circuit of affected module which is not communicating for an open. See appropriate wiring diagram in «DATA LINK CONNECTORS»(ref-8610) article in WIRING DIAGRAMS. If an open does not exist, go to next step. If an open exists, repair wiring as necessary. After repairs are complete, go to step 9.
5. Inspect for poor connections at related connectors for power supply circuit(s), ground circuit(s), and class 2 serial data circuit of affected control module which is not communicating. Repair faults as necessary. After repairs are complete, go to step 9. If all related connections are okay, go to next step.
6. Replace control module which is not communicating properly. Go to step 9.
7. Select DISPLAY DTC function for control module which had U1000-U1255 set as a current DTC. If scan tool displays any DTC that does not begin with a "U", perform appropriate diagnostic system check for affected control module. See «TROUBLE SHOOTING»(ref-9085-S02717531962000100500000). If scan tool displays any "U" type DTCs, go to next step.
8. Using scan tool, record and clear all DTCs. Repair is complete.
9. Select DISPLAY DTC function for control module which stored loss of communications with XXX DTC. If scan tool displays any DTC that does not begin with "U", perform appropriate diagnostic system check for control module in which DTCs are stored. See «TROUBLE SHOOTING»(ref-9085-S02717531962000100500000). If scan tool displays any "U" type DTCs, go to next step.
10. Using scan tool, record and clear all DTCs. If no DTCs are stored, system is okay. If any DTCs remain, diagnose and repair DTCs until all control modules have been diagnosed, and all DTCs have been cleared.