4. Low Beam Headlights Do Not Light Up, Bulbs Are OK

CIRCUIT OPERATION
The FRONT-ECU receives a ON signal from the low-beam side headlight relay, and supplies current to the headlights through dedicated fuse 11 and 12.

TECHNICAL DESCRIPTION (COMMENT)
If neither the left nor right low-beam headlight lights up, there may be a fault in the low-beam side headlight relay or the FRONT-ECU.

TROUBLESHOOTING HINTS
- Damaged harness wires or connectors
- Malfunction of the headlight relay (LOW)
- Malfunction of the FRONT-ECU

DIAGNOSIS
Required Special Tool:
MB991223: Harness Set

STEP 1. Check headlight (LOW) relay for continuity.
1. Remove the headlight (LOW) relay.







2. Check headlight (LOW) relay for continuity.
If the headlight (LOW) relay is in good condition, go to Step 2.
If the headlight (LOW) relay is faulty, replace it. Check that the malfunction is eliminated.




STEP 2. Check headlight relay connector A-08X for damage.
If headlight relay connector A-08X is damaged, repair or replace it. Refer to Harness Connector Inspection.
If harness connector A-08X is in good condition, go to Step 3.




STEP 3. Check the harness wires between headlight relay (LOW) connector A-08X and the battery.
If the harness wires between headlight relay (LOW) connector A-08X and the battery are damaged, repair them.
Go to Step 4.




STEP 4. Check the headlight (LOW) power source.
1. Remove the headlights (both sides).
2. Measure at the harness side of headlight connectors A-27 and A-32.
3. Measure voltage between terminal number 1 and the ground at the column switch LOW position.
- The voltage should be approximately 12 volts (battery positive voltage).
If approximately 12 volts, go to Step 5.
If not approximately 12 volts, go to Step 6.




STEP 5. Check the harness wires between headlight connectors A-27, A-32 and the body ground.
If the harness wires between headlight connectors A-27, A-32 and the body ground are damaged, repair them. Check that the malfunction is eliminated.







STEP 6. Check the harness wires between headlight connector A-27 (LH), headlight connector A-32 (RH) and headlight relay (LOW) connector A-08X.
If the harness wires between headlight connector A-27 (LH), headlight connector A-32 (RH) and headlight relay (LOW) connector A-08X are damaged, repair them.
Check that the malfunction is eliminated.
If the harness wires are in good condition, go to Step 7.






NOTE: After inspecting intermediate connector C-05, inspect the wire. If intermediate connector C-05 is damaged, repair or replace it. Refer to Harness Connector Inspection.




STEP 7. Check harness connector A-09X for damage.
If connector A-09X is damaged, repair or replace it. Refer to Harness Connector Inspection.
If connector A-09X is in good condition, go to Step 8.




STEP 8. Check the harness wires between FRONT-ECU A-08X and headlight relay (LOW) A-08X.
If the harness wires between FRONT-ECU A-09X and headlight relay (LOW) A-08X are damaged, repair them.
Check that the malfunction is eliminated.
If the harness wires are in good condition, go to Step 9.

Step 9. Check symptoms.
Confirm that the headlight (LOW) is illuminated.