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Headlights - Automatic Twilight Sentinel Cadillac Catera I

Headlights 7 illustrations ~3818 words

DESCRIPTION & OPERATION

Automatic twilight sentinel determines automatic on/off control of exterior lights, and holds exterior lights on for a period of time after ignition switch is turned to OFF position. Twilight sentinel system consists of the BCM, twilight sentinel delay switch and twilight sentinel ON/OFF switch (integral with headlight switch).

Body Control Module (BCM) controls twilight sentinel system and Daytime Running Lights (DRL) system (high beam headlights at half-intensity). DRL can be overridden by twilight sentinel and wiper ON operation. BCM is supplied input of ambient light condition by A/C-heater control which uses ambient light sensor. A twilight delay switch is used to determine the twilight delay after ignition switch is turned to OFF position. Twilight delay can be adjusted from 3 to 180 seconds in response to voltage level at twilight delay input.

System operates automatically whenever ignition is on, headlights are off, and twilight sentinel system is on. When turned on, system automatically turns on exterior lights at dusk. At dawn, system will turn exterior lights off.

System provides a delay period before switching lights on or off. This prevents system from operating under sudden ambient lighting changes (such as passing through tunnels or exposure to bright lights at night). Delay period is 2 seconds when switching from day to night, and 40 seconds when switching from night to day. Amount of delay can be changed by using a scan tool.

SERVICE PRECAUTIONS - HANDLING

CAUTIONWhen handling Electrostatic Discharge (ESD) sensitive electronic parts (control modules), take special care to avoid damaging components.
  1. Discharge personal static electricity by momentarily touching metal grounding point on vehicle before touching electronic components.
  2. DO NOT touch terminals on components or connectors with fingers or metal tools. When unplugging connectors, DO NOT let metal tool contact any exposed terminal.
  3. Never jumper, ground or use test probes on components or connectors unless specified in diagnosis. ALWAYS connect ground lead first.
  4. DO NOT remove solid-state components from protective packaging until ready for installation. Touch packaging to ground before opening.
  5. DO NOT bump or drop components. DO NOT place component on metal work bench, metal objects or electrically operated components (such as radio, TV or oscilloscope).

COMPONENT LOCATIONS

ComponentLocation
Body Control Module (BCM)Lower Right-Side "A" Pillar, Behind Trim Panel
Daytime Running Light (DRL) RelayUnder Instrument Panel, Right Of Steering Column
Fuse BlockUnder Instrument Panel, Lower Left Of Steering Wheel
Headlight Automatic Control Ambient Light SensorTop Center Of Instrument Panel
Headlight Relays (All)Under Instrument Panel, Right Of Steering Column
Transmission Range Switch (TRS)Left Side Of Transmission Housing

COMPONENT LOCATIONS

PRELIMINARY INSPECTION

  1. Check fuses in instrument panel fuse block. If any fuse is open, check for short to ground in appropriate circuit. Ensure battery voltage exists at input side of each fuse. If battery voltage does not exist, see appropriate wiring diagram under POWER DISTRIBUTION in SYSTEM WIRING DIAGRAMS article.
  2. If one headlight is inoperative, check bulb, connections and related wiring. See appropriate wiring diagram in HEADLIGHT SYSTEMS & DAYTIME RUNNING LIGHTS article. Ensure all ground connections are clean and tight.
  3. Check for poor connections or broken wires inside of insulation which could cause an intermittent. Check for proper installation of aftermarket electronic equipment.

HEADLIGHT SYSTEM CHECK

  1. Check fuses in instrument panel fuse block. Using DVOM, check for voltage between input side of each fuse and ground. If battery voltage exists, go to step 3). If battery voltage does not exist, go to next step.
  2. Locate and repair problem in power distribution circuits. See appropriate wiring diagram under POWER DISTRIBUTION in SYSTEM WIRING DIAGRAMS article. Go to step 5).
  3. If all fuses are okay, go to step 5). If any fuse is blown, use DVOM to check for continuity between output side of appropriate fuse and ground. If continuity does not exist, replace fuse and go to step 5). If continuity exists, go to next step.
  4. Locate and repair short to ground in appropriate circuit. See appropriate wiring diagram in HEADLIGHT SYSTEMS & DAYTIME RUNNING LIGHTS article in the WIRING DIAGRAMS section. Go to next step.
  5. Install scan tool. Establish communication with BCM. Check for any existing Diagnostic Trouble Codes (DTCs). If any DTCs exist, go to next step. If no DTCs exist, go to step 7).
  6. Locate and repair problem in BCM system. See «BODY CONTROL MODULES»(/cadillac/catera/i-1996-2001/remont/body-cab-control-systems/#body-control-module) article.
  7. Turn headlights on. Check low beam headlight operation. If low beam headlights operate properly, go to next step. If low beam headlights do not operate properly, go to «LOW BEAM HEADLIGHTS INOPERATIVE»(/cadillac/catera/i-1996-2001/remont/headlights/#headlights-automatic-twilight-sentinel__low-beam-headlights-inoperative) under SYSTEM TESTING.
  8. Check high beam headlight operation. If high beam headlights operate properly, go to step 10). If high beam headlights do not operate properly, go to next step.
  9. If both high beam headlights are inoperative, go to «HIGH BEAM HEADLIGHTS INOPERATIVE»(/cadillac/catera/i-1996-2001/remont/headlights/#headlights-automatic-twilight-sentinel__high-beam-headlights-inoperative) under SYSTEM TESTING. If only left-side high beam headlight is inoperative, go to «LEFT-SIDE HIGH BEAM HEADLIGHT INOPERATIVE»(/cadillac/catera/i-1996-2001/remont/headlights/#headlights-automatic-twilight-sentinel__left-side-high-beam-headlight-inoperative) under SYSTEM TESTING. If only right-side high beam headlight is inoperative, go to «RIGHT-SIDE HIGH BEAM HEADLIGHT INOPERATIVE»(/cadillac/catera/i-1996-2001/remont/headlights/#headlights-automatic-twilight-sentinel__right-side-high-beam-headlight-inoperative) under SYSTEM TESTING.
  10. Press and release flash-to-pass switch. If flash-to-pass system operates properly, go to next step. If flash-to-pass system does not operate properly, go to «FLASH-TO-PASS INOPERATIVE»(/cadillac/catera/i-1996-2001/remont/headlights/#headlights-automatic-twilight-sentinel__flash-to-pass-inoperative) under SYSTEM TESTING.
  11. Start engine. Place gearshift lever in any position except Park. Ensure Daytime Running Lights (DRL) are operating properly. If DRL operate properly, go to next step. If DRL do not operate properly, go to «DAYTIME RUNNING LIGHTS (DRL) INOPERATIVE»(/cadillac/catera/i-1996-2001/remont/headlights/#headlights-automatic-twilight-sentinel__daytime-running-lights-drl-inoperative) under SYSTEM TESTING.
  12. Turn twilight sentinel system on. Cover ambient light sensor with a dark cloth. If twilight sentinel system operates properly, headlight system is operating properly. If twilight sentinel system does not operate properly, go to «TWILIGHT SENTINEL INOPERATIVE»(/cadillac/catera/i-1996-2001/remont/headlights/#headlights-automatic-twilight-sentinel__twilight-sentinel-inoperative) under SYSTEM TESTING.

SYSTEM TESTING

WARNINGBefore servicing instrument panel components on vehicles with Supplemental Inflatable Restraint (SIR) system, disable SIR system. See DISABLING & ACTIVATING AIR BAG SYSTEM in AIR BAG RESTRAINT SYSTEMS article.
CAUTIONTo prevent damage to terminals, Connector Test Adaptor Kit (J-35616-A) must be used whenever a diagnostic procedure requires checking or probing terminals.

Note. For twilight sentinel system wiring diagrams, see HEADLIGHT SYSTEMS & DAYTIME RUNNING LIGHTS article.

LOW BEAM HEADLIGHTS INOPERATIVE

Note. Perform headlight system check before proceeding. See HEADLIGHT SYSTEM CHECK under TROUBLE SHOOTING.

  1. Disconnect headlight switch harness connector. Using DVOM, measure resistance between headlight switch harness connector terminal No. 13 (Black wire) and ground. (Scheme 1) If resistance is less than 5 ohms, go to step 3). If resistance is 5 ohms or greater, go to next step.
  2. Repair open or high resistance in circuit F18 (Black wire) between headlight switch and ground. Go to step 10).
  3. Reconnect headlight switch harness connector. Disconnect 32-pin BCM harness connector C2 (Brown). BCM is mounted on right-side "A" pillar, behind trim panel. Turn headlights on. Using DVOM, measure resistance between BCM harness connector C2, terminal D10 (Yellow wire) and ground. (Scheme 2) If resistance is less than 5 ohms, go to step 5). If resistance is 5 ohms or greater, go to next step.
  4. Check for open or high resistance in circuit B899 (Yellow wire) or B60 (Yellow wire) between BCM harness connector C2 and headlight switch. If circuits are okay, replace headlight switch. Go to step 10).
  5. Remove low beam relay (K131) from relay box. Using DVOM, measure voltage between low beam relay socket terminal No. 5 (Red wire) and ground. (Scheme 3) If battery voltage exists, go to step 7). If battery voltage does not exist, go to next step.
  6. Repair open or high resistance in circuit A814 (Red wire) between low beam relay and power distribution fuse block (located at left front of engine compartment). Go to step 10).
  7. Connect a fused jumper wire between low beam relay socket terminals No. 4 (Yellow wire) and No. 5 (Red wire). If low beam headlights illuminate, go to step 9). If low beam headlights do not illuminate, go to next step.
  8. Repair open or high resistance in circuit B50 (Yellow wire) between low beam relay and fuse block. Go to step 10).
  9. Replace low beam relay. Go to next step.
  10. Reconnect all disconnected components and harness connectors. Check low beam headlight operation. If low beam headlights illuminate, system is operating properly. If low beam headlights do not illuminate, go to step 1).

Scheme 1

Scheme 1
Scheme 1

Scheme 2

Scheme 2
Scheme 2

Scheme 3

Scheme 3
Scheme 3

HIGH BEAM HEADLIGHTS INOPERATIVE

Note. Perform headlight system check before proceeding. See HEADLIGHT SYSTEM CHECK under TROUBLE SHOOTING.

Scheme 4

Scheme 4: HIGH BEAM HEADLIGHTS INOPERATIVE
Scheme 4: HIGH BEAM HEADLIGHTS INOPERATIVE

Scheme 5

Scheme 5
Scheme 5
  1. Turn low beam headlights on. Disconnect turn signal switch harness connector (integral with multifunction switch, on left side of steering column). Using DVOM, measure voltage between turn signal switch harness connector terminal No. 1 (Yellow wire) and ground. (Scheme 4) If battery voltage exists, go to step 3). If battery voltage does not exist, go to next step.
  2. Repair open or high resistance in circuit B905 (Yellow wire) and/or B800 (Yellow wire) between turn signal switch and fuse block. Go to step 11).
  3. Reconnect turn signal switch harness connector. Disconnect 24-pin BCM harness connector C1 (Brown). BCM is mounted on right-side "A" pillar, behind trim panel. Turn high beam headlights on. Using DVOM, measure voltage between BCM harness connector C1, terminal A04 (White wire) and ground. (Scheme 2) If battery voltage exists, go to step 5). If battery voltage does not exist, go to next step.
  4. Check for open or high resistance in circuit M3 (White wire) and/or M50 (White wire) between turn signal switch and BCM harness connector C1. If circuits are okay, replace turn signal switch. See «STEERING COLUMN SWITCHES»(/cadillac/catera/i-1996-2001/remont/steering-column-switches/#steering-column-switches) article. Go to step 11).
  5. Remove Daytime Running Lights (DRL) relay (K133) from relay box. Turn high beam headlights on. Using DVOM, measure voltage between DRL relay socket terminal No. 1 (Brown/Purple wire) and ground. (Scheme 5) If voltage does not exist, go to step 7). If battery voltage exists, go to next step.
  6. Check for short to battery voltage in circuit XY802 (Brown/Purple wire) between DRL relay and BCM harness connector C2. If circuit is okay, replace BCM. See «BODY CONTROL MODULES»(/cadillac/catera/i-1996-2001/remont/body-cab-control-systems/#body-control-module) article. Go to step 11).
  7. Remove left-side high beam headlight relay (K73) from relay box. Turn high beam headlights on. Using DVOM, measure voltage between left-side high beam headlight relay socket terminal No. 1 (White wire) and ground. If voltage does not exist, go to step 9). If battery voltage exists, go to next step.
  8. Check for short to battery voltage in circuit M60 (White wire) and/or M69 (White wire) between left-side high beam highlight relay and BCM harness connector C2. If circuit is okay, replace BCM. See «BODY CONTROL MODULES»(/cadillac/catera/i-1996-2001/remont/body-cab-control-systems/#body-control-module) article. Go to step 11).
  9. Remove right-side high beam headlight relay (K132) from relay box. Turn high beam headlights on. Using DVOM, measure voltage between right-side high beam headlight relay socket terminal No. 6 (White wire) and ground. If voltage does not exist, go to step 11). If battery voltage exists, go to next step.
  10. Repair short to battery voltage in circuit M62 (White wire) between left-side high beam headlight relay and right-side high beam headlight relay. Go to next step.
  11. Reconnect all disconnected components and harness connectors. Check high beam headlight operation. If high beam headlights illuminate, system is operating properly. If high beam headlights do not illuminate, go to step 1).

LEFT-SIDE HIGH BEAM HEADLIGHT INOPERATIVE

Note. Perform headlight system check before proceeding. See HEADLIGHT SYSTEM CHECK under TROUBLE SHOOTING.

  1. Remove Daytime Running Lights (DRL) relay (K133) and left-side high beam headlight relay (K73) from relay box. Using DVOM, measure voltage between ground and DRL relay socket terminals No. 3 (Red wire) and No. 5 (Red wire). (Scheme 5) Measure voltage between left-side high beam headlight relay socket terminal No. 3 (Red wire) and ground. If battery voltage exists at both terminals, go to step 3). If battery voltage does not exist at both terminals, go to next step.
  2. Repair open or high resistance in circuit A10 (Red wire), A825 (Red wire) and/or A832 (Red wire) between DRL relay, left-side high beam headlight relay and fuse block. Go to step 10).
  3. Turn high beam headlights on. Using DVOM, measure voltage between DRL relay socket terminal No. 1 (Brown/Purple wire) and ground. Measure voltage between left-side high beam headlight relay socket terminal No. 1 (White wire) and ground. If voltage does not exist at both terminals, go to step 5). If battery voltage exists at both terminals, go to next step.
  4. Check for short to battery voltage in circuit XY802 (Brown/Purple wire), M60 (White wire) and/or M69 (White wire) between DRL relay, BCM harness connector C2 and left-side high beam highlight relay. If circuits are okay, replace BCM. See «BODY CONTROL MODULES»(/cadillac/catera/i-1996-2001/remont/body-cab-control-systems/#body-control-module) article. Go to step 10).
  5. Disconnect left-side high beam headlight harness connector. Using DVOM, measure voltage between left-side high beam headlight harness connector terminal "E" (White wire) and ground. If battery voltage exists, go to step 7). If battery voltage does not exist, go to next step.
  6. Check for open or high resistance in circuit M8 (White wire) and/or M2 (White wire) between left-side high beam headlight and DRL relay. If circuits are okay, replace DRL relay. Go to step 10).
  7. Using DVOM, measure resistance between left-side high beam headlight harness connector terminal "B" (Black/White wire) and ground. If resistance is less than 5 ohms, go to step 9). If resistance 5 ohms or greater, go to next step.
  8. Check for open or high resistance in circuit FM13 (Black/White wire), FM19 (Black/White wire) and/or F803 (Black wire) between left-side high beam headlight, left-side high beam headlight relay and ground. If circuits are okay, replace left-side high beam headlight relay. Go to step 10).
  9. Replace left-side high beam headlight. Go to next step.
  10. Reconnect all disconnected components and harness connectors. Check left-side high beam headlight operation. If left-side high beam headlight illuminates, system is operating properly. If left-side high beam headlight does not illuminate, go to step 1).

RIGHT-SIDE HIGH BEAM HEADLIGHT INOPERATIVE

Note. Perform headlight system check before proceeding. See HEADLIGHT SYSTEM CHECK under TROUBLE SHOOTING.

  1. Remove right-side high beam headlight relay (K132) from relay box. Using DVOM, measure voltage between ground and right-side high beam headlight relay socket terminals No. 4 (Red wire) and No. 2 (Red wire). (Scheme 3) If battery voltage exists at both terminals, go to step 3). If battery voltage does not exist at both terminals, go to next step.
  2. Repair open or high resistance in circuit A827 (Red wire) and/or A850 (Red wire) between right-side high beam headlight relay and fuse block. Go to step 10).
  3. Turn high beam headlights on. Using DVOM, measure voltage between right-side high beam headlight relay socket terminal No. 6 (White wire) and ground. If voltage does not exist, go to step 5). If battery voltage exists, go to next step.
  4. Check for short to battery voltage in circuit M62 (White wire) between right-side high beam headlight relay and left-side high beam headlight relay. If circuit is okay, replace BCM. See «BODY CONTROL MODULES»(/cadillac/catera/i-1996-2001/remont/body-cab-control-systems/#body-control-module) article. Go to step 10).
  5. Disconnect right-side high beam headlight harness connector. Using DVOM, measure voltage between right-side high beam headlight harness connector terminal "E" (White wire) and ground. If battery voltage exists, go to step 7). If battery voltage does not exist, go to next step.
  6. Check for open or high resistance in circuit M64 (White wire) and/or M1 (White wire) between right-side high beam headlight and right-side high beam headlight relay. If circuits are okay, replace right-side high beam headlight relay. Go to step 10).
  7. Using DVOM, measure resistance between right-side high beam headlight harness connector terminal "B" (Black wire) and ground. If resistance is less than 5 ohms, go to step 9). If resistance is 5 ohms or greater, go to next step.
  8. Repair open or high resistance in circuit F11 (Black wire) between right-side high beam headlight and ground. Go to step 10).
  9. Replace right-side high beam headlight. Go to next step.
  10. Reconnect all disconnected components and harness connectors. Check right-side high beam headlight operation. If right-side high beam headlight illuminates, system is operating properly. If right-side high beam headlight does not illuminate, go to step 1).

FLASH-TO-PASS INOPERATIVE

Note. Perform headlight system check before proceeding. See HEADLIGHT SYSTEM CHECK under TROUBLE SHOOTING.

  1. Disconnect 24-pin BCM harness connector C1 (Brown). Press and hold flash-to-pass switch. Using DVOM, measure voltage between BCM harness connector C1, terminal A04 (White wire) and ground. (Scheme 2) If battery voltage exists, go to next step. If battery voltage does not exist, go to step 3).
  2. Replace BCM. See «BODY CONTROL MODULES»(/cadillac/catera/i-1996-2001/remont/body-cab-control-systems/#body-control-module) article. Go to step 8).
  3. Disconnect turn signal switch harness connector (integral with multifunction switch, on left side of steering column). Using DVOM, measure resistance between BCM harness connector C1, terminal A04 (White wire) and turn signal switch harness connector terminal No. 2 (White wire). If resistance is less than 5 ohms, go to step 5). If resistance is 5 ohms or greater, go to next step.
  4. Repair high resistance or open in circuit M3 (White wire) and/or M50 (White wire) between BCM and turn signal switch. go to step 8).
  5. Using DVOM, measure voltage between turn signal switch harness connector terminal No. 5 (Red wire) and ground. If battery voltage exists, go to step 7). If battery voltage does not exist, go to next step.
  6. Repair high resistance or open in circuit A8 (Red wire) between turn signal switch and fuse block. Go to step 8).
  7. Replace turn signal switch. See «STEERING COLUMN SWITCHES»(/cadillac/catera/i-1996-2001/remont/steering-column-switches/#steering-column-switches) article. Go to next step.
  8. Reconnect all disconnected components and harness connectors. Check flash-to-pass operation. If flash-to-pass operates properly, system is operating properly. If flash-to-pass does not operate properly, go to step 1).

DAYTIME RUNNING LIGHTS (DRL) INOPERATIVE

Note. Perform headlight system check before proceeding. See HEADLIGHT SYSTEM CHECK under TROUBLE SHOOTING.

  1. Remove DRL relay (K133) from relay box. Turn ignition switch to RUN position. Apply parking brake. Move gearshift lever from Park. Using DVOM, measure voltage between DRL relay socket terminal No. 5 (Red wire) and ground. (Scheme 5) If battery voltage exists, go to step 3). If battery voltage does not exist, go to next step.
  2. Repair open or high resistance in circuit A10 (Red wire) between DRL relay and fuse block. Go to step 9).
  3. Reinstall DRL relay. Disconnect left-side high beam headlight harness connector. Using DVOM, measure voltage between left-side high beam headlight harness connector terminal "E" (White wire) and ground. If battery voltage exists, go to step 5). If battery voltage does not exist, go to next step.
  4. Check for open or high resistance in circuit M8 (White wire) and/or M2 (White wire) between left-side high beam headlight and DRL relay. If circuits are okay, replace DRL relay. Go to step 9).
  5. Reconnect left-side high beam headlight harness connector. Disconnect right-side high beam headlight harness connector. Using DVOM, measure voltage between right-side high beam headlight harness connector terminal "E" (White wire) and ground. If battery voltage exists, go to step 7). If battery voltage does not exist, go to next step.
  6. Check for open or high resistance in circuits M1 (White wire), M64 (White wire), M65 (White wire), FM19 (Black/White wire) or FM13 (Black/White wire). If circuits are okay, replace left-side high beam headlight relay. Go to step 9).
  7. Using DVOM, measure resistance between right-side high beam headlight harness connector terminal "B" (Black wire) and ground. If resistance is less than 5 ohms, go to step 9). If resistance is 5 ohms or greater, go to next step.
  8. Repair open or high resistance in circuit F11 (Black wire) between right-side high beam headlight and ground. Go to next step.
  9. Reconnect all disconnected components and harness connectors. Check DRL operation. If DRL operate properly, system is operating properly. If DRL do not operate properly, go to step 1).

TWILIGHT SENTINEL INOPERATIVE

Note. Perform headlight system check before proceeding. See HEADLIGHT SYSTEM CHECK under TROUBLE SHOOTING.

Scheme 6

Scheme 6: TWILIGHT SENTINEL INOPERATIVE
Scheme 6: TWILIGHT SENTINEL INOPERATIVE

Scheme 7

Scheme 7
Scheme 7
  1. Disconnect 24-pin BCM harness connector C1 (Brown). Turn twilight sentinel system on. Using DVOM, measure resistance between BCM harness connector C1, terminal A07 (Red/Yellow wire) and ground. (Scheme 2) If resistance is less than 5 ohms, go to step 3). If resistance is 5 ohms or greater, go to next step.
  2. Check for open or high resistance in circuit AB810 (Red/Yellow wire) between BCM harness connector C1 and headlight switch. If circuit is okay, replace headlight switch. Go to step 13).
  3. Disconnect ambient light sensor harness connector. Using DVOM, measure voltage between ambient light sensor harness connector terminal No. 1 (Brown wire) and ground. (Scheme 6) If voltage is 5 volts, go to step 5). If voltage is not 5 volts, go to next step.
  4. Check for open or high resistance in circuit X812 (Brown wire) between ambient light sensor and A/C-heater control. If circuit is okay, replace A/C-heater control assembly. See «DEFOGGER - MIRROR & REAR WINDOW»(/cadillac/catera/i-1996-2001/remont/heated-glassdefoggers/#defogger-mirror-rear-window) article. Go to step 13).
  5. Disconnect A/C-heater control harness connector. Using DVOM, measure resistance between ambient light sensor harness connector terminal No. 3 (Black wire) and A/C-heater control harness connector terminal No. 2 (Black wire). (Scheme 7) If resistance is less than 5 ohms, go to step 7). If resistance is 5 ohms or greater, go to next step.
  6. Repair open or high resistance in circuit X830 (Black wire) between ambient light sensor and A/C-heater control. Go to step 13).
  7. Install scan tool. Select outside status on scan tool. Using scan tool, check input at BCM harness connector C1, terminal A01 (Brown/Blue wire). If input is near battery voltage, scan tool should indicate daytime. If input is not as specified, scan tool should indicate night time. If scan tool indicates either display, go to step 12). If scan tool does not indicate either display, go to next step.
  8. Ensure ambient light sensor harness connector is disconnected. Ensure BCM harness connector C1 is disconnected. Connect a fused jumper wire between ambient light sensor harness connector terminals No. 1 (Brown wire) and No. 3 (Black wire). Using DVOM, measure voltage between BCM harness connector C1, terminal A01 (Brown/Blue wire) and ground. (Scheme 2)and (Scheme 7). If voltage does not exist, go to step 10). If battery voltage exists, go to next step.
  9. Check for short to voltage in circuit XP830 (Brown/Blue wire) and/or XP33 (Brown/Blue wire) between BCM harness connector C1 and A/C-heater control. If circuits are okay, replace A/C-heater control assembly. See «DEFOGGER - MIRROR & REAR WINDOW»(/cadillac/catera/i-1996-2001/remont/heated-glassdefoggers/#defogger-mirror-rear-window) article. Go to step 13).
  10. Remove jumper wire. Using DVOM, measure voltage between BCM harness connector C1, terminal A01 (Brown/Blue wire) and ground. If battery voltage exists, go to step 12). If battery voltage does not exist, go to next step.
  11. Check for short to ground, open or high resistance in circuit XP830 (Brown/Blue wire) and/or XP33 (Brown/Blue wire) between BCM harness connector C1 and A/C-heater control. If circuits are okay, replace A/C-heater control assembly. See «DEFOGGER - MIRROR & REAR WINDOW»(/cadillac/catera/i-1996-2001/remont/heated-glassdefoggers/#defogger-mirror-rear-window) article. Go to step 13).
  12. Replace BCM. See «BODY CONTROL MODULES»(/cadillac/catera/i-1996-2001/remont/body-cab-control-systems/#body-control-module) article. Go to next step.
  13. Reconnect all disconnected components and harness connectors. Check twilight sentinel system operation. If twilight sentinel operates properly, system is operating properly. If twilight sentinel does not operate properly, go to step 1).

REMOVAL & INSTALLATION

WARNINGBefore servicing instrument panel components on vehicles with Supplemental Inflatable Restraint (SIR) system, disable SIR system. See DISABLING & ACTIVATING AIR BAG SYSTEM in AIR BAG RESTRAINT SYSTEMS article.
CAUTIONWhen battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION section before disconnecting battery.

Ambient light sensor is mounted in defroster grille. Using small flat-bladed screwdriver, pry sensor from instrument panel. Disconnect electrical harness connector. To install, reverse removal procedure.

WIRING DIAGRAMS

Note. For twilight sentinel system wiring diagrams, see HEADLIGHT SYSTEMS & DAYTIME RUNNING LIGHTS article.