Headlights - Automatic Twilight Sentinel Chevrolet Caprice Impala SS

DESCRIPTION

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). A photocell is mounted on top of the dash to sense light levels. When the headlights are turned on, or photocell senses darkness, input to the control module is grounded, and the module applies power to exterior lighting circuits.

OPERATION

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

The system provides a 30-second delay before switching lights on or off, thus preventing the 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. Before performing any instrument panel testing, diagnosis, or repair, disable SIR system by disconnecting negative battery cable and 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 still 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.

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, never 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.

Components Possibly Damaged By ESD

1. ABS Controller.
2. Central Control Module (CCM).
3. Chime Module And Cruise Control Module.
4. Distributorless Ignition System (DIS) Module.
5. Electronic Instrument Cluster Panel (IPC).
6. Electronic Control Module (ECM) (Including PROM, CAL-PAK, Or MEM-CAL).
7. HVAC Electronic A/C-Heater Controllers And Modules.
8. Power Control Module (PCM).
9. Radio And Theft Deterrent Modules.
10. Twilight Sentinel Module Or Amplifier.

Preliminary Trouble Shooting

1. Check headlight system operation with manual switch. If all headlights operate okay manually, but twilight sentinel does not operate properly, find 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

Loose connection at headlight switch or module connector. Open wiring between fusible link and headlight switch. Inoperative headlight switch or circuit breaker. Open in ground path through on-off switch of time-delay control of sentinel switch. Inoperative photocell or module.

Lights Do Not Turn Off In Daylight

Inoperative or obstructed photocell. Poor contact between photocell and socket, or socket disengaged from mounting hole. Faulty module.

Lights Do Not Turn Off After Ignition Is Off

Fuse blown. Inoperative time delay control. Open wiring. Inoperative module. Malfunctioning photocell.

Lights Do Not Stay On Proper Time Span After Ignition Is Off

Inoperative time delay control. High resistance at module connector. Short in wiring. Inoperative module.

Warning Chime Does Not Operate

Open wire in chime circuit. Inoperative door jam switch. Poor connection at headlight switch. Inoperative module. Blown fuse. Time delay control malfunction.

DIAGNOSIS & TESTING

TWILIGHT SENTINEL SYSTEM OPERATION TEST

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

Without DRL

1. Turn headlights off. Turn ignition on. Set twilight sentinel control to mid position. Cover photocell on top of instrument panel with cardboard. All exterior lighting should come on within 30 seconds.
2. Uncover photocell. Expose photocell to sunlight or bright incandescent light. All exterior lights should turn off within 30 seconds.
3. Again cover photocell with cardboard. Wait until exterior lights come on, then turn ignition off. All exterior lights should turn off after a few minutes delay. Delay depends on position of twilight sentinel switch. With switch in MAX position, lights could remain on for about 3-4 minutes. If system performs as described, twilight sentinel system is operating properly. If system does not perform as described, see appropriate TEST PROCEDURE.

With DRL

1. Turn headlights off. Turn ignition on. Set twilight sentinel switch to mid position. Cover photocell on top of instrument panel with cardboard. All exterior lights should come on within 30 seconds.
2. Uncover photocell. Expose photocell to sunlight or bright incandescent light. All exterior lights should turn off within 30 seconds.
3. Again cover photocell with cardboard. Wait until exterior lights come on, then turn ignition off. All exterior lights should turn off after a few minutes delay. Delay depends on twilight sentinel switch position. With switch in MAX position, lighting could remain on for about 4 minutes.
4. Turn ignition on. Set twilight sentinel control to MIN position. Expose photocell to sunlight or bright incandescent light. Move gear selector lever out of "P" position. Body lights should come on, together with headlights at reduced intensity. Set gear selector lever to "P" position. Body lights should remain on, but headlights should turn off. If lights operate as specified, system is operating properly. If system does not perform as described, see appropriate TEST PROCEDURE.

Exterior Lights Are On During Daylight

1. Turn twilight sentinel on. Turn ignition on. Remove photocell light sensor. See TWILIGHT SENTINEL PHOTOCELL under REMOVAL & INSTALLATION.
2. Connect fused jumper wire between both photocell sensor connector terminals (Light Green/Black and Yellow/Black wires). If headlights turn off, replace photocell sensor. If headlights stay on, go to next step.
3. Test for open in Light Green/Black or Yellow wire, or for poor connections at photocell or module. Locate lamp control module (behind right kick/trim panel). Inspect for poor connections at module Blue C1 connector terminals "G" (Light Green/Black wire) and "H" (Yellow/Black wire). If wires and connections are good, temporarily substitute known good lamp control module, then retest system.

Twilight Sentinel Turns On Headlights Only

1. Locate lamp control module (behind right kick/trim panel). Using a grounded test light, backprobe lamp control module Black C2 connector terminal "A" (Orange wire). (Scheme 1) If battery voltage exists, go to next step. If battery voltage does not exist, inspect for open in Orange wire between lamp control module and fuse No. 14, repair as necessary.
2. Turn ignition on. Turn twilight sentinel on. Cover photocell on top of instrument panel. Using a grounded test light backprobe lamp control module Black C2 connector, terminal "H" (Brown wire). If battery voltage exists, repair open in Brown wire from lamp control module to fuse panel. If battery voltage does not exist, inspect Brown wire for poor connection at module. If connection is good, temporarily substitute known good lamp control module, then retest system.

Scheme 1

Twilight Sentinel Turns On Body Lights Only

1. Turn twilight sentinel on. Turn ignition on. Cover photocell, located on top of instrument panel. Locate lamp control module, behind right kick panel.
2. Backprobe lamp control module Black C2 connector, terminal "F" (Yellow wire). If battery voltage exists, repair open in Yellow wire between lamp control module and dimmer switch.
3. If battery voltage does not exist, inspect for poor connection of Yellow wire at module connector. If connection is okay, temporarily substitute known good lamp control module, then retest system.

Normally

1. Turn headlights off. Locate lamp control module (behind right kick/trim panel). Using a grounded test light, backprobe lamp control module Black C2 connector terminal "D" (Dark Green/White wire). If battery voltage exists, go to next step. If battery voltage does not exist, go to step 11).
2. Turn ignition on. Backprobe lamp control module Blue C1 connector, terminal "E" (Pink wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Pink wire between lamp control module and fuse No. 17.
3. With a test light, backprobe between module Blue C1 connector terminals "D" (Black wire) and "E" (Pink wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Black wire to ground.
4. Turn twilight sentinel off. Measure voltage at lamp control module connector C1, terminal "A" (Light Green wire). If battery voltage exists, go to next step. If battery voltage does not exist, inspect for poor connection at terminal "A". If connection is okay, temporarily substitute known good lamp control module, then retest system.
5. Measure voltage at twilight sentinel switch terminal "B" (Light Green wire). If battery voltage exists, go to next step. If battery voltage does not exist, inspect for open circuit in Light Green wire from lamp control module to switch.
6. Using test light, backprobe between twilight sentinel switch terminals "B" (Light Green wire) and "C" (Black/White wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair Black/White wire from terminal "C" to ground.
7. Unplug photocell sensor. If headlights and body lights are not on, go to next step. If headlights and body lights come on, replace photocell sensor.
8. Measure voltage at photocell connector Light Green/Black wire. If battery voltage does not exist, go to next step. If battery voltage exists, inspect Light Green/Black wire for short to voltage. If wire is okay, temporarily substitute known good lamp control module, then retest system.
9. Inspect Light Green/Black wire for shorts or open circuit between photocell sensor and twilight sensor module. If wire is okay, measure voltage between Light Green/Black and Yellow/Black wires at photocell sensor connector. If battery voltage exists, go to next step. If battery voltage does not exist, inspect Yellow/Black wire for open. If wire is okay, replace lamp control module.
10. Inspect for poor connections at twilight sentinel switch. If connections are okay, replace switch.
11. Using test light, backprobe Green/White wire at headlight switch. If battery voltage exists, inspect switch connections. If connections are okay, replace switch. If battery voltage does not exist, inspect for open circuit in Green/White wire between switch and lamp control module.

Headlight Delay Inoperative

1. Turn ignition on. Turn twilight sentinel on. Turn headlights off. Using DVOM, backprobe twilight sentinel switch connector terminals "A" (Purple wire) and "D" (Black/White wire).
2. Observe meter while moving twilight sentinel delay control slowly from MIN to MAX position. If voltage does not exist, go to step 3). If voltage varies, temporarily substitute known good lamp control module, then retest system. If battery voltage exists but does not change, inspect for poor connection at terminal "D" (Black/White wire) of twilight sentinel switch. If Black/White wire terminal connection is good, replace twilight sentinel switch.
3. Locate lamp control module (behind right kick/trim panel). Using DVOM, backprobe lamp control module Blue C1 connector, terminal "F" (Purple wire). If battery voltage does not exist, inspect for poor connection at Purple wire terminal at lamp control module connector. If connection is good, replace lamp control module. If battery voltage exists, repair open in Purple wire between twilight sentinel switch and lamp control module.

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. Remove right kick/trim panel. Remove screws, unplug connectors, and remove module. To install, 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 Wiring Diagram. Scheme 2

See also:
• COMPUTER RELEARN PROCEDURES