Horn Relay: Testing and Inspection

WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE, THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE BEFORE PERFORMING FURTHER DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.

Relay Test
The horn relay is located in the Junction Block (JB) on the right cowl side inner panel below the instrument panel in the passenger compartment. Remove the relay from the JB to perform the following tests.

Fig.4 ISO Relay - Typical:

1. A relay in the de-energized position should have continuity between terminals 87A and 30, and no continuity between terminals 87 and 30. If OK, go to Step 2. If not OK, replace the faulty relay.
2. Resistance between terminals 85 and 86 (electromagnet) should be 75 ± 5 ohms. If OK, go to Step 3. If not OK, replace the faulty relay.
3. Connect a battery to terminals 85 and 86. There should now be continuity between terminals 30 and 87, and no continuity between terminals 87A and 30. If OK, refer to RELAY CIRCUIT TEST. If not OK, replace the faulty relay.

Relay Circuit Test
1. Check for continuity between the horn relay control circuit cavity (30) of the JB horn relay receptacle and a good ground. There should be continuity with the horn switch depressed and none with the horn switch released. If OK, go to Step 2. If not OK, refer to horn switch for the proper diagnosis and testing procedure.
2. Disconnect the headlamp and dash wire harness connectors for both horns from the horn connector receptacles. Check for continuity between the horn relay output circuit cavity (87) of the JB horn relay receptacle and the horn relay output circuit cavity of the headlamp and dash wire harness connector for each horn. There should be continuity. If OK, go to Step 3. If not OK, repair the open horn relay output circuit as required.
3. Check for battery voltage at the fused B(+) circuit cavity (86) of the JB horn relay receptacle. If OK, go to Step 4. If not OK, repair the open fused B(+) circuit to the fuse (Fuse 4 - 50 ampere) in the Power Distribution Center (PDC) as required.
4. Check for battery voltage at the fused B(+) circuit cavity (30) of the JB horn relay receptacle. If OK, refer to horn for the proper diagnosis and testing procedure. If not OK, repair the open fused B(+) circuit to the fuse (Fuse 21 - 15 ampere) in the JB as required.