Headlights - Automatic Twilight Sentinel Cadillac DeVille Concours

DESCRIPTION & OPERATION

Headlights on vehicles equipped with twilight sentinel system are controlled by a Lamp Control Module (LCM), Daytime Running Lights (DRL) Module, or Central Control Module (CCM). An ambient light sensor (photocell), mounted to top of instrument panel or under left defroster grille, is used to sense light levels. When headlights are turned on, or photocell senses darkness, input to control module is grounded, and module applies power to exterior lighting circuits.

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 30-second delay before switching lights on or off, thus preventing system from operating under sudden ambient lighting changes, such as passing through tunnels or exposure to bright lights at night.

AIR BAG PRECAUTIONS

Observe following precautions when working on vehicles equipped with Supplemental Inflatable Restraint (SIR) air bag systems

1. Disable SIR system before performing any instrument panel testing, diagnosis or repair. Turn wheels to straight-ahead position. Turn ignition switch to LOCK position. Remove AIR BAG or SIR fuse. Disconnect Yellow 2-pin connector at base of steering column.
2. To enable SIR system to power down, wait 20 minutes before making any repairs. System back-up power supply retains enough voltage to deploy air bag for a short time after battery is disconnected.
3. To avoid accidental air bag deployment, avoid Yellow SIR wiring harnesses when trouble shooting, repairing, or replacing instrument panel components. All SIR wiring harnesses are Yellow.
4. To activate system, reverse procedure. Turn ignition switch to RUN position. Verify air bag warning light flashes 7-9 times and then goes out.

HANDLING PRECAUTIONS

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 put component on metal work bench, metal objects, or electrically operated components, such as radio, TV, or oscilloscope.

PRELIMINARY TROUBLE SHOOTING

1. Check headlight system operation with manual switch. If all headlights operate okay manually, but twilight sentinel does not operate properly, proceed to test with appropriate symptom. If headlights do not operate properly with manual switch, go to next step.
2. If headlight do not operate at all, inspect all fuses and circuit breakers. If fuses repeatedly blow, check problem circuit for short to ground. If any headlight is dim, inspect ground connections. If one headlight is inoperative, inspect suspect bulb. After making any repair recheck headlight system function.

LIGHTS DO NOT AUTOMATICALLY TURN ON IN DARKNESS

Check for loose connection at headlight switch or module connector. Check for open wiring between fusible link and headlight switch, inoperative headlight switch or circuit breaker. Check for open in ground path through on-off switch of time-delay control of sentinel switch. Check for inoperative photocell or module.

LIGHTS DO NOT TURN OFF IN DAYLIGHT

Check for inoperative or obstructed photocell. Check for poor contact between photocell and socket, socket disengaged from mounting hole, or faulty module.

LIGHTS DO NOT TURN OFF AFTER IGNITION IS OFF

Check for blown fuse, inoperative time delay control, open wiring, inoperative module or malfunctioning photocell.

LIGHTS DO NOT STAY ON PROPER TIME SPAN AFTER IGNITION IS OFF

Check for inoperative time delay control or high resistance at module connector. Check for short in wiring or inoperative module.

WARNING CHIME DOES NOT OPERATE

Check for open wire in chime circuit, inoperative door jam switch or poor connection at headlight switch. Check for inoperative module, blown fuse or time delay control malfunction.

DIAGNOSIS

Note. Unless otherwise specified, make all measurements with a digital volt-ohmmeter with an input impedance of 10 megohms.

SYSTEM CHECK (WITHOUT DRL)

1. Turn low beam headlights on. If low beams do not turn on, go to «TEST "A", HEADLIGHTS INOPERATIVE»(/cadillac/deville-concours/1994-1998/remont/headlights/#headlights-automatic-twilight-sentinel__test-a-headlights-inoperative) . Turn ignition, twilight sentinel, and headlights off. If exterior lights are off, go to next step. If exterior lights remain on, go to «TEST "B", LIGHTS DO NOT TURN OFF»(/cadillac/deville-concours/1994-1998/remont/headlights/#headlights-automatic-twilight-sentinel__test-b-lights-do-not-turn) .
2. Turn ignition on. Turn headlights off. Turn twilight sentinel on. Cover photocell on top of instrument cluster with dark paper. Exterior lights should turn on after about 30 seconds. If lights do not turn on, go to TEST "C", TWILIGHT SENTINEL/DRL INPUT TEST.
3. Uncover photocell. Expose photocell to sunlight or bright incandescent light. Exterior lights should turn off within 30 seconds. If lights do not turn off, go to TEST "C", TWILIGHT SENTINEL/DRL INPUT TEST.
4. Cover photocell. Wait for lights to turn on. Turn ignition off. Set twilight sentinel control to MAX delay position. Lights should turn off after about 3 minutes. If lights turn off, system is working properly. If lights do not turn off, go to TEST "C", TWILIGHT SENTINEL/DRL INPUT TEST.

SYSTEM CHECK (WITH DRL)

1. Turn low beam headlights on. If low beams do not turn on, go to «TEST "A", HEADLIGHTS INOPERATIVE»(/cadillac/deville-concours/1994-1998/remont/headlights/#headlights-automatic-twilight-sentinel__test-a-headlights-inoperative) . Turn ignition, twilight sentinel, and headlights off. If exterior lights are off, go to next step. If exterior lights remain on, proceed to the «TEST "B", LIGHTS DO NOT TURN OFF»(/cadillac/deville-concours/1994-1998/remont/headlights/#headlights-automatic-twilight-sentinel__test-b-lights-do-not-turn) .
2. Turn headlights off. Set gear selector to Park. Turn ignition on. If headlights and exterior lights are off, go to next step. If headlights and exterior lights are on, go to TEST "C", TWILIGHT SENTINEL/DRL INPUT TEST.
3. Apply parking brake. Expose photocell to sunlight or bright incandescent light. Set gear selector to Drive. If headlights are on and exterior lights are off, go to next step. If headlights are off and/or exterior lights are on, go to TEST "C", TWILIGHT SENTINEL/DRL INPUT TEST.
4. Set gear selector to Park. Turn ignition on. Turn headlights off. Turn twilight sentinel on. Cover photocell with dark paper. If exterior lights turn on after about 30 seconds, go to next step. If exterior lights do not turn on after about 30 seconds, go to «TEST "C", TWILIGHT SENTINEL/DRL INPUT TEST»(/cadillac/deville-concours/1994-1998/remont/headlights/#headlights-automatic-twilight-sentinel__test-c-twilight-sentineldrl-input-test) .
5. Set twilight sentinel control to MAX delay position. Turn ignition off. If exterior lights turn off after about 3 minutes, system is working properly. If operation is not as described, go to TEST "C", TWILIGHT SENTINEL/DRL INPUT TEST.

TEST "A", HEADLIGHTS INOPERATIVE

1. Turn headlights on. Set dimmer switch to high beam position. If high beam headlights are off, go to next step. If high beams are on, inspect dimmer switch. If dimmer switch is okay, repair Tan wire between dimmer switch and engine compartment fuse block.
2. Turn ignition on. Cover photocell. Turn twilight sentinel on. If headlights do not turn on, go to next step. If headlights turn on, replace headlight switch.
3. Disconnect headlight relay "D" located in engine compartment micro relay center. Measure voltage at relay connector terminals No. 1 (Orange wire) and No. 3 (Orange wire). If battery voltage exists at each terminal, go to next step. If battery voltage does not exist, repair appropriate Orange wire.
4. Turn ignition off. Turn headlights on. Measure resistance between relay connector terminal No. 2 (Yellow wire) and ground. If resistance is less than 3 ohms, go to step 6). If resistance is more than 3 ohms, go to next step.
5. Disconnect headlight switch connector. Install headlight relay "D". Measure voltage at switch connector C1, terminal "C" (Yellow wire). (Scheme 1)and (Scheme 2). If battery voltage does not exist, repair open in Yellow wire. If battery voltage exists, inspect Black wire at headlight switch for open between switch and chassis ground. If Black wire is okay, replace headlight switch.
6. Connect 30-amp fused jumper between headlight relay "D", terminals No. 3 (Orange wire) and 5 (Light Blue wire). If headlights do not turn on, go to next step. If headlights turn on, replace relay "D".
7. With jumper in place, measure voltage at terminal C5 (Yellow wire) at 48-pin connector located left of steering column. If battery voltage exists, replace dimmer switch. If battery voltage does not exist, repair open or short to voltage in Light Blue wire between headlight relay "D" and dimmer switch.

Scheme 1

Scheme 2

TEST "B", LIGHTS DO NOT TURN OFF

1. Disconnect headlight switch connectors. If lights remain on, go to next step. If lights are off, replace headlight switch.
2. Disconnect DRL module, at rear of headlight switch. Reconnect headlight switch connectors. If headlights go out, replace DRL module. If lights remain on, replace headlight switch.

TEST "C", TWILIGHT SENTINEL/DRL INPUT TEST

1. Disconnect headlight switch connectors. Measure voltage between headlight switch connector C1, terminal "A" (Orange wire) and ground. (Scheme 1)and (Scheme 2). If battery voltage exists, go to next step. If battery voltage does not exist, repair Orange wire between fuse block in trunk and headlight switch connector.
2. Measure voltage at headlight switch connector C1, terminal "B" (Pink wire). If battery voltage exists, repair short to battery voltage in Pink wire. If battery voltage does not exist, turn ignition on. Measure voltage at headlight switch connector C1, terminal "B" (Pink wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short to ground in Pink wire.
3. Measure resistance between headlight switch connector C1, terminals "J" (Black wire) and "H" (White wire). Cover photocell and record resistance. Uncover photocell and record resistance with photocell exposed to bright incandescent light or sunlight.
4. Resistance should be more than 90 k/ohms with photocell covered and less than 72 k/ohms with photocell exposed to light. If resistance is not as specified, go to TEST "D", TWILIGHT SENTINEL PHOTOCELL TEST. If resistance is as specified, measure resistance between headlight switch connector C1, terminal "H" (White wire) and ground.
5. If resistance is less than 100 k/ohms, go to TEST "D", TWILIGHT SENTINEL PHOTOCELL TEST. If resistance is more than 100 k/ohms and vehicle is equipped with daytime running lights, go to next step. If resistance is more than 100 k/ohms and vehicle is not equipped with daytime running lights, test headlight switch. See «HEADLIGHT SWITCH TESTING»(/cadillac/deville-concours/1994-1998/remont/headlights/#headlights-automatic-twilight-sentinel__headlight-switch-testing).
6. Apply parking brake. Using DVOM, measure voltage at headlight switch connector C1, terminal "L" (Light Green wire). Set gear selector to Park. Record voltage. Set gear selector to Drive. Record voltage. Battery voltage should exist with gear selector in Park. No voltage should exist with gear selector in Drive.
7. If voltages are as specified, go to next step. If voltages are not as specified, repair Light Green wire between headlight switch connector and park/neutral position switch. If wire is okay, replace park/neutral position switch.
8. Connect fused jumper between ground and headlight switch connector C1, terminal "M" (Light Green/Black wire). If headlights do not turn on, inspect daytime running lights relay. If headlights turn on, go to «HEADLIGHT SWITCH TESTING»(/cadillac/deville-concours/1994-1998/remont/headlights/#headlights-automatic-twilight-sentinel__headlight-switch-testing).

TEST "D", TWILIGHT PHOTOCELL TEST

1. Reconnect headlight switch. Remove twilight sentinel photocell. See «TWILIGHT SENTINEL PHOTOCELL»(/cadillac/deville-concours/1994-1998/remont/headlights/#headlights-automatic-twilight-sentinel) under REMOVAL & INSTALLATION. Disconnect photocell connector. Turn ignition on. Measure voltage at photocell harness connector terminal "A" (White wire).
2. If voltage is not 5 volts, repair White wire between photocell and headlight switch connector C1, terminal "H". If voltage is 5 volts, measure voltage between photocell harness connector terminals. If voltage is not 5 volts, repair open in Black wire between photocell and headlight switch connector C1, terminal "J". If voltage is 5 volts, replace photocell.

HEADLIGHT SWITCH TESTING

Remove headlight/twilight switch assembly. Test for continuity or measure resistance between specified terminals. See HEADLIGHT SWITCH TESTING table. For terminal identification (Scheme 3) If measurements are as specified, replace DRL module. If measurements are not as specified, replace headlight switch.

HEADLIGHT SWITCH TESTING

REMOVAL & INSTALLATION

TWILIGHT SENTINEL CONTROL MODULE

Note. Twilight sentinel may be also known as daytime running light module, lamp control module or central control module.

Disconnect negative battery cable. Twilight sentinel/DRL module plugs directly into headlight switch assembly. To remove control module, remove headlight switch. Remove 2 screws securing module to left switch pod. Remove module and disconnect electrical connector. To install module, reverse removal procedure.

Depending on model, photocell is either mounted under left defroster grille or secured to top of instrument panel. Unsnap defroster grille. Twist photocell counterclockwise to disengage photocell and socket. Unplug connector. To install, reverse removal procedure.

Headlight System & Daytime Running Lights Wiring Diagram (Concours & DeVille). Scheme 3

See also:
• COMPUTER RELEARN PROCEDURES
• AIR BAG PRECAUTIONS
• TEST "A", HEADLIGHTS INOPERATIVE
• TEST "B", LIGHTS DO NOT TURN OFF
• TEST "C", TWILIGHT SENTINEL/DRL INPUT TEST
• HEADLIGHT SWITCH TESTING
• TWILIGHT SENTINEL PHOTOCELL