Toyota
Jeep Cherokee
 Service Manual
Lamps » Lamp diagnosis
System diagnosis

HEADLAMP

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

Conventional and halogen headlamps are interchangeable.

It is recommended that they not be intermixed on a given vehicle.

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 Z1-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 Z1-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 Z1-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 Z1-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 Z1-ground.
  2.  High resistance in headlamp circuit.
  3.  Faulty headlamp switch.
  4.  Loose or corroded terminals or splices in circuit.
  1.  Test for voltage drop across Z1-ground locations, refer to Group 8W.
  2.  Test amperage draw of headlamp circuit. Should not exceed 30 amps.
  3. Replace headlamp switch. Refer to Group 8E.
  4.  Inspect and repair all connectors and splices, refer to Group 8W.
HEADLAMPS DO NOT ILLUMINATE
  1. No voltage to headlamps.
  2.  No Z1-ground at headlamps.
  3.  Faulty headlamp switch.
  4.  Faulty headlamp dimmer (multi-function) switch.
  5.  Broken connector terminal or wire splice in headlamp circuit.
  1.  Repair open headlamp circuit, refer to Group 8W.
  2. Repair circuit ground, refer to Group 8W.
  3. Replace headlamp switch. Refer to Group 8E.
  4.  Replace multi-function switch.
  5.  Repair connector terminal or wire splice.
*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 Z1-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 Z1-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 Z1-ground.
  3.  High resistance in fog lamp circuit.
  1.  Test and repair charging system. Refer to Group 8A.
  2.  Test for voltage drop across Z1-ground locations. Refer to Group 8W.
  3.  Test amperage draw of fog lamp circuit.
FOG LAMPS FLASH RANDOMLY
  1. Poor lighting circuit Z1-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 Z1-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 Z1-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.  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

HEADLAMP DELAY MODULE

DELAY FUNCTION INOPERATIVE

(1) Ensure headlamps operate before proceeding.

(2) Remove, inspect and test the HDLP delay 10 amp fuse in junction box. Replace if defective.

(3) With the key off and the connector disconnected, measure the resistance from the delay module connector, terminal 4 to vehicle body ground. The ohmmeter should indicate zero ohms. If not, repair the open circuit in the wire harness to vehicle body ground.

(4) With the key on measure the voltage between the delay module connector, terminal 8 and vehicle body ground. The voltmeter should indicate battery voltage. If not, repair the open circuit in the wire harness from ignition switch to HDLP delay module.

(5) Turn headlamps on and measure voltage at delay module connector, terminal 6. The voltmeter should indicate battery voltage. If not repair open circuit between L2 and HDLP delay module.

(6) Measure the voltage between the delay module connector, terminal 2 and vehicle body ground. The voltmeter should indicate battery voltage. If not, repair the open circuit in the wire harness to the HDLP fuse in the PDC.

(7) If steps 1 through 6 prove out good, replace headlamp delay module.

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