Inspection Procedure 5

Inspection Procedure 5: One of the headlights does not illuminate.

CAUTION:
If the discharge type headlights do not illuminate, fully understand the precautions in "Service precautions for discharge headlight" before proceeding with the troubleshooting. Refer to Headlight.






















TECHNICAL DESCRIPTION (COMMENT)

When one of the headlights does not illuminate, the wiring harness, connector(s), or the bulb may have a problem, or the fuse may be burned out.

TROUBLESHOOTING HINTS

- Malfunction of the headlight bulbs

- Malfunction of the headlight assembly

- Malfunction of the headlamp control unit

- Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:

- MB992006: Extra fine probe

- MB991223: Harness set

STEP 1. Check headlight (LOW) connector A-37 [LH], A-56 [RH] for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is headlight (LOW) assembly connector A-37 [LH], A-56 [RH] in good condition?

YES Go to Step 2.
NO Repair the defective connector.
STEP 2. Check bulb.

Check the bulb(s) of headlight that does not illuminate.

NOTE:
If discharge-type lower beam headlights do not illuminate, their bulbs cannot be inspected. In this case, assume the bulbs to be normal and proceed with steps.

Q. Is the bulb in good condition?

YES Go to Step 3.
NO Replace the bulb(s) of the light that does not illuminate.
STEP 3. Check the ground circuit to the headlight assembly (LOW). Measure the resistance at headlight assembly (LOW) connector A-37 [LH], A-56 [RH].

(1)Disconnect the connector, and measure at the wiring harness side.









(2)Resistance between the connector of light which does not illuminate and ground.

- Resistance between the A-37 (LH), A-56 (RH) headlight assembly connector terminal 6 and ground. [Halogen headlight (LOW)]

- Resistance between the A-37 (LH), A-56 (RH) headlight assembly connector terminal 5 and ground. [Discharge headlight (LOW)]
OK: The resistance should be 2 ohms or less.

Q. Is the measured resistance 2 ohms or less?

YES Go to Step 5.

NO Go to Step 4.

STEP 4. Check the wiring harness between headlight assembly (LOW) connector A-37 [LH], A-56 [RH] (terminal 6 [halogen headlight] or 5 [discharge headlight]) and ground.

- Check the ground wires for open circuit.

Q. Is the wiring harness between headlight assembly (LOW) connector A-37 [LH], A-56 [RH] (terminal 6 [halogen headlight] or 5 [discharge headlight]) and ground in good condition?

YES The trouble can be an intermittent malfunction How to Cope With Intermittent Malfunctions).
NO The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. Verify that the headlights illuminate normally.
STEP 5. Check the wiring harness between headlight assembly (LOW) connector A-37 [LH], A-56 [RH] (terminal 1 and 2 [halogen headlight] or 1 and 12 [discharge headlight]) and headlight relay (LOW) connector A-28X or headlight relay (HIGH) connector A-20X (terminal 3).

- Check the power supply line for open circuit.

Q. Is the wiring harness between headlight assembly (LOW) connector A-37 [LH], A-56 [RH] (terminal 1 and 2 [halogen headlight] or 1 and 12 [discharge headlight]) and headlight relay (LOW) connector A-28X or headlight relay (HIGH) connector A-20X (terminal 3) in good condition?

YES Replace the headlight assembly that does not illuminate.
NO The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. Verify that the headlights illuminate normally.