Headlight Relay Circuit

LIGHTING: LIGHTING SYSTEM: Headlight Relay Circuit

Headlight Relay Circuit

DESCRIPTION

The main body ECU receives a signal from the light control switch, and turns on the low beam headlights.
HINT:
- The headlight relays are installed in the power distributor, so unlike conventional relays, it cannot be removed for inspection.
- If only a low beam headlight bulb on one side does not illuminate, inspect the bulb, fuse, or wire harness that is related to the bulb.
- If both right and left low beam headlights do not illuminate when the light control switch is turned to the HEAD position, read the light control switch HEAD signal value in the data list and perform the headlight relay active test to determine if the malfunction exists on either the switch side or the relay side.

WIRING DIAGRAM









INSPECTION PROCEDURE

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM
(a) Connect Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn Techstream on.
(d) Select the following menu items: Body Electrical / Main Body / Active Test.
(e) Check that the relays operate.

Main Body:





OK:
Headlight relays operate. (LO-beam headlights illuminate.)
OK -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
NG -- Continue to next step.
2. INSPECT ENGINE ROOM JUNCTION BLOCK ASSEMBLY




(a) Remove the H-LP (RL) fuse and H-LP (LL) fuse from the engine room junction block assembly.
(b) Measure the voltage between the loading slot of each fuse and body ground.
Standard voltage:






OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (FUSE - BODY GROUND)
NG -- Continue to next step.
3. INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY




(a) Measure the voltage according to the value(s) in the table below.
Standard voltage:






OK -- REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY
NG -- Continue to next step.
4. INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY




(a) Disconnect the DD instrument panel junction block assembly connector.
(b) Measure the voltage according to the value(s) in the table below.
Standard voltage:






OK -- REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY
NG -- Continue to next step.
5. INSPECT ENGINE ROOM JUNCTION BLOCK LOCK ASSEMBLY




(a) Disconnect the 1D engine room J/B assembly connector.
(b) Measure the voltage according to the value(s) in the table below.
Standard voltage:






OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE ROOM J/B ASSEMBLY - INSTRUMENT PANEL J/B ASSEMBLY)
NG -- Continue to next step.
6. CHECK HARNESS AND CONNECTOR (BATTERY - ENGINE ROOM J/B ASSEMBLY)




(a) Disconnect the 1G engine room junction block assembly connector.
(b) Measure the voltage according to the value(s) in the table below.
Standard voltage:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY