Lamp diagnosis

DIAGNOSIS AND TESTING

SYSTEM DIAGNOSIS

A good ground is necessary for proper lighting operation. Grounding is provided by the lamp socket when it comes in contact with the metal body, or through a separate ground wire.

Always begin any diagnosis by testing all of the fuses and circuit breakers in the system. Refer to Group 8W, Wiring Diagrams.

HEADLAMP

CONDITION POSSIBLE CAUSES CORRECTION
HEADLAMPS ARE DIM WITH ENGINE IDLING OR IGNITION TURNED OFF 1. Loose or corroded battery cables.

2. Loose or worn generator drive belt.

3. Charging system output too low.

4. Battery has insufficient charge.

5. Battery is sulfated or shorted.

6. Poor lighting circuit Z3-ground.

7. Both headlamp bulbs defective.

1. Clean and secure battery cable clamps and posts.

2. Adjust or replace generator drive belt.

3. Test and repair charging system, refer to Group 8A,

4. Test battery state-of -charge , refer to Group 8A.

5. Load test battery, refer to Group 8A.

6. Test for voltage drop across Z3-ground locations, refer to Group 8W.

7. Replace both headlamp bulbs.

HEADLAMP BULBS BURN OUT FREQUENTLY 1. Charging system output too high.

2. Loose or corroded terminals or splices in circuit.

1. Test and repair charging system, refer to Group 8A.

2. Inspect and repair all connectors and splices, refer to Group 8W.

HEADLAMPS ARE DIM WITH ENGINE RUNNING ABOVE IDLE* 1. Charging system output too low.

2. Poor lighting circuit Z3-ground.

3. High resistance in headlamp circuit.

4. Both headlamp bulbs defective.

1. Test and repair charging system, refer to Group 8A.

2. Test for voltage drop across Z3-ground locations, refer to Group 8W.

3. Test amperage draw of headlamp circuit.

4. Replace both headlamp bulbs.

HEADLAMPS FLASH RANDOMLY 1. Poor lighting circuit Z3-ground.

2. High resistance in headlamp circuit.

3. Loose or corroded terminals or splices in circuit.

1. Test for voltage drop across Z3-ground locations, refer to Group 8W.

2. Test amperage draw of headlamp circuit.

3. Inspect and repair all connectors and splices, refer to Group 8W.

HEADLAMPS (HIGH & LOW) DO NOT ILLUMINATE 1. No voltage at either headlamp.

2. No ground for high and low beam circuit.

3. Headlamp bulb(s) defective.

4. Faulty headlamp switch.

5. Faulty headlamp dimmer (Multifunction) switch.

6. Broken connector terminal or wire splice in headlamp circuit.

1. Voltage should always be present. Trace short circuit and replace BOTH headlamp fuses. Refer to Group 8W. Check wiring circuit from Right headlamp fuse to headlamp. (Repeat for Left side)

2. Ground should always be present according to switch position. Check ground at headlamp switch. Check wiring circuit from headlamp switch to Multifunction switch. Check headlamp switch and Multifunction switch continuity. Repair circuit ground, refer to Group 8W.

3. Replace bulb(s).

4. Replace headlamp switch.

5. Replace Multifunction switch.

6. Repair connector terminal or wire splice.

HEADLAMPS (LOW BEAM) DO NOT ILLUMINATE. 1. No ground for low beam circuit. 1. Ground should be present according to Multifunction switch position. Check wiring circuit from Multifunction switch to headlamp. Trace open circuit in wiring and repair. Refer to Group 8W.

Check Multifunction Switch for continuity.

HEADLAMPS (HIGH BEAM) DO NOT ILLUMINATE. 1. No ground for high beam circuit. 1. Ground should be present according to Multifunction switch position. Check wiring circuit from Multifunction switch to headlamp. Trace open circuit in wiring and repair. Refer to Group 8W.

Check Multifunction Switch for continuity.

HEADLAMPS (LOW BEAM) ALWAYS ILLUMINATE AND CAN NOT BE SHUT OFF. 1. Low beam circuit from bulb to Multifunction switch is shorted to ground. 1. Ground should be present according to Multifunction switch position. Check wiring circuit from Multifunction switch to headlamp. Trace short circuit in wiring and repair. Refer to Group 8W.
HEADLAMPS (HIGH BEAM) ALWAYS ILLUMINATE AND CAN NOT BE SHUT OFF. 1. High beam circuit from bulb to Multifunction switch is shorted to ground. 1. Ground should be present according to Multifunction switch position. Check wiring circuit from Multifunction switch to headlamp. Trace short circuit in wiring and repair. Refer to Group 8W.
HEADLAMP SWITCH OFF HEADLAMPS AND HIGHBEAM INDICATOR REMAIN ON AND ARE DIM. 1. Headlamp switch feed circuit shorted to ground. 1. Check wiring circuit from right headlamp fuse to headlamp. Repeat for left side.

Trace short circuit in wiring and repair.

Refer to Group W.

HEADLAMP SWITCH ON (LOW BEAMS ON), ONE LOW BEAM ON AND BOTH HIGH BEAMS DIM. 1. Headlamp feed circuit shorted to ground. 1. Check wiring circuit from right headlamp fuse to headlamp. Repeat for left side.

Trace short circuit in wiring and repair.

Refer to Group W.

HEADLAMP SWITCH ON (HIGH BEAMS ON), ONE HIGH BEAM ON AND BOTH LOW BEAMS DIM. 1. Headlamp feed circuit shorted to ground. 1. Check wiring circuit from right headlamp fuse to headlamp. Repeat for left side.

Trace short circuit in wiring and repair.

Refer to Group W.

HEADLAMP SWITCH ON, ONE HEADLAMP FILAMENT WILL BE AT FULL INTENSITY AND ALL OTHER FILAMENTS ARE ON AND DIM. 1. Blown headlamp fuse.

2. Open circuit from headlamp fuse to headlamp.

1. Trace short circuit and replace fuse.

Refer to Group 8W.

2. Repair open headlamp circuit, refer to Group 8W.

1. HEADLAMPS STAY ON WITH KEY OUT (DRLM EQUIPPED VEHICLES). 1. Failed DRLM 1. Replace DRLM.
*Canada vehicles must have lamps ON.

FOG LAMP

CONDITION POSSIBLE CAUSES CORRECTION
FOG LAMPS ARE DIM WITH ENGINE IDLING OR IGNITION TURNED OFF. 1. Loose or corroded battery cables.

2. Loose or worn generator drive belt.

3. Charging system output too low.

4. Battery has insufficient charge.

5. Battery is sulfated or shorted.

6. Poor lighting circuit Z3-ground.

1. Clean and secure battery cable clamps and posts.

2. Adjust or replace generator drive belt.

3. Test and repair charging system. Refer to Group 8A,

4. Test battery state-of -charge. Refer to Group 8A.

5. Load test battery. Refer to Group 8A.

6. Test for voltage drop across Z3-ground locations. Refer to Group 8W.

FOG LAMP BULBS BURN OUT FREQUENTLY 1. Charging system output too high

2. Loose or corroded terminals or splices in circuit.

1. Test and repair charging system. Refer to Group 8A.

2. Inspect and repair all connectors and splices. Refer to Group 8W.

FOG LAMPS ARE DIM WITH ENGINE RUNNING ABOVE IDLE 1. Charging system output too low.

2. Poor lighting circuit Z3-ground.

3. High resistance in fog lamp circuit.

1. Test and repair charging system. Refer to Group 8A.

2. Test for voltage drop across Z3-ground locations. Refer to Group 8W.

3. Test amperage draw of fog lamp circuit.

FOG LAMPS FLASH RANDOMLY 1. Poor lighting circuit Z3-ground.

2. High resistance in fog lamp circuit.

3. Faulty fog lamp switch.

4. Loose or corroded terminals or splices in circuit.

1. Test for voltage drop across Z3-ground locations. Refer to Group 8W.

2. Test amperage draw of fog lamp circuit.

3. Replace fog lamp switch.

4. Inspect and repair all connectors and splices. Refer to Group 8W.

FOG LAMPS DO NOT ILLUMINATE 1. Blown fuse for fog lamp.

2. No Z3-ground at fog lamps.

3. Faulty fog lamp switch.

4. Broken connector terminal or wire splice in fog lamp circuit.

5. Defective or burned out bulb.

1. Trace short and replace fuse. Refer to Group 8W.

2. Repair circuit ground. Refer to Group 8W.

3. Replace fog lamp switch.

4. Repair connector terminal or wire splice.

5. Replace bulb.

FOG LAMPS ARE INOPERATIVE AND FOG LAMP INDICATOR LIGHT ALWAYS STAYS ON. 1. Fog lamp/DRL* feed shorted to ground. 1. Check wiring circuit from fog lamp/DRL* fuse to fog lamp. Trace short circuit in wiring and repair. Refer to Group 8W.
FOG LAMPS ARE INOPERATIVE AND FOG LAMP INDICATOR LIGHT IS ILLUMINATED. 1. Fog lamp/DRL* fuse defective.

2. Open circuit from fog lamp fuse to fog lamp.

1. Trace short circuit and replace fuse.

Refer to Group 8W.

2. Check wiring circuit from fog lamp/DRL* fuse to fog lamp. Trace open circuit in wiring and repair. Refer to Group 8W.

PARK LAMPS ARE INOPERATIVE. FOG LAMP INDICATOR IS ON WHEN ALL SWITCHES ARE OFF AND FUNCTIONS OPPOSITE TO FOG LAMPS. 1. Park lamp feed is shorted. 1. Check wiring circuit from park lamp fuse to headlamp switch. Trace short circuit in wiring and repair. Refer to Group 8W.
PARK LAMPS ARE INOPERATIVE. FOG LAMP INDICATOR FUNCTIONS OPPOSITE TO FOG LAMPS. 1. Park lamp fuse is defective.

2. Open circuit from park lamp fuse to headlamp switch.

1. Trace short circuit and replace fuse.

Refer to Group 8W.

2. Check wiring circuit from park lamp fuse to headlamp switch. Trace open circuit in wiring and repair. Refer to Group 8W.

*Canada vehicles use Daytime Running Lamps (DRL).
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