Headlight Relay Circuit

HEADLIGHT RELAY CIRCUIT

CIRCUIT DESCRIPTION

The multiplex network body ECU controls headlight relay (H-LP R, H-LP L) when signal is received from the headlamp dimmer switch assy.

The headlight relay installed in the power distributor.

a. Description

1. The power distributor installed in the J/B No.2 uses the no-contact type relay with a semiconductor.
2. The power distributor has a function to protect the power distributor circuit if overcurrent is applied to the power distributor or overheating occurs.
Protect function operates under the following conditions:
- Malfunction is detected in the wire harness connected to the J/B No.2.
- Malfunction is detected in the interior relay of the J/B No.2.

3. The power distributor has a mode monitor terminal for external checking of the operating condition (normal or protect condition) of the power distributor,
4. The operating condition (normal or protect condition) of the semiconductor relay can be checked using the output voltage from the mode monitor terminal.

NOTE: Check that no DTCs are output in the ABS and VSC motor relay.
If any DTC (C0273/13, C0274/14, C1361/91) is detected, inspect the ABS and VSC motor relay in accordance with the troubleshooting of the brake system.

5. When the semiconductor relay is operating normally, the mode monitor terminal outputs approximately 6 V. When the semiconductor relay operates in protect mode, the mode monitor terminal outputs about 0 V. However, the mode monitor terminal outputs for the overall operating condition of the power distributor, so it is not possible to specify the semiconductor relay during protect operation.

6. When the fail-safe function operates, the power distributor performs the following operations:
- Stops the operation of the troubled semiconductor relay only.
- Stops the power supply to the troubled semiconductor relay circuit only.

HINT: Normal semiconductor relay or circuit operates properly.

7. While the fail-safe function operates, check for a short circuit in the following areas:
- Wire harness driven by relay on the terminal side and body ground.
- Inside the power distributor (including the semiconductor relay)

b. Recovery from Fail-Safe

1. The power distributor soon restores the semiconductor relay function, but if a load abnormality still continues, the power distributor again stops the semiconductor relay function. (except Rr-DEF Relay)
2. The power distributor and the semiconductor relay function stop until the rear defogger switch turns on again.

Then the rear defogger switch turns on again, the semiconductor relay function recovers, but if the load abnormality is not corrected by this time, the Power Distributor again stops the semiconductor relay function.

If the load abnormality is corrected, the semiconductor relay function recovers when the rear defogger switch turns on again. (Rr-DEF Relay)

System Diagram Part 1:

System Diagram Part 2:

Wiring Diagram:

Step 1 - 2:

Step 3:

Step 4:

Step 4 (Continued):

Step 5:

Step 6:

Step 7:

Step 8:

Step 9:

INSPECTION PROCEDURE

HINT: Start the inspection from step 1 when using the hand-held tester, and start from step 2 when not using the hand-held tester.