Horn Circuit Troubleshooting

NOTE:

	SRS components are located in this area. Review the SRS component locations, and precautions and procedures before performing repairs or servicing.
	Refer to the Electrical Wiring Diagrams for the location of the under-dash fuse/relay box connector.

Problem verification:

Problem verification

?1.	Push the horn switch.

Does the horn sound?


	YES

Intermittent failure, the system is OK at this time. Check for loose or poor connections.?


	NO

Go to step 2.

Fuse check:

Fuse check

?1.

Check the following fuse.

Fuse	No. A5 (10 A)
Location	Under-hood fuse/relay box

Is the fuse OK?


	YES

Go to step 3.


	NO

Replace the fuse, and recheck. If the fuse blows again, repair a short in the No. A5 (10 A) fuse circuit.?

Horn relay check:

Horn relay check

?1.	Remove the horn relay from the under-hood fuse/relay box, and test it.

Is the relay OK?


	YES

Go to step 4.


	NO

Replace the horn relay, then recheck.?

Open wire check (+B HORN line):

Open wire check (+B HORN line)

?1.

Measure the voltage between test points 1 and 2.

Test condition	IG LOCK (0) or OFF mode Horn relay: disconnected
Test circuit	+B HORN
Test point 1	Horn relay 4P socket No. 1 (RED)
Test point 2	Body ground

Test point 1	Horn relay 4P socket No. 3 (RED)
Test point 2	Body ground

Is there battery voltage?


	YES

The +B HORN wire is OK. Go to step 5.


	NO

Repair an open or high resistance in the wire.?

Determine possible failure area (horn relay switch side circuit, horn relay coil side circuit):

Determine possible failure area (horn relay switch side circuit, horn relay coil side circuit)

?1.	Connect terminals A and B with a jumper wire.

?2.

Connect terminals A and B with a jumper wire.

Terminal A	Horn relay 4P socket No. 1 (RED)
Terminal B	Horn relay 4P socket No. 2 (BLU)

Does the horn sound?


	YES

Go to step 6.


	NO

Go to step 13.

Open wire check (HORN RLY CL- line):

Open wire check (HORN RLY CL- line)

?1.	Disconnect the jumper wire.

?2.	Reinstall the horn relay.

?3.

Measure the voltage between test points 1 and 2.

Test condition	IG LOCK (0) or OFF mode
Test circuit	HORN RLY CL-
Test point 1	Under-dash fuse/relay box connector E (36P) No. 34 (TAN)
Test point 2	Body ground

Is there battery voltage?


	YES

The HORN RLY CL- wire is OK. Go to step 7.


	NO

Repair an open or high resistance in the wire.?

Determine possible failure area (HORN SW line, under-dash fuse/relay box internal circuit):

Determine possible failure area (HORN SW line, under-dash fuse/relay box internal circuit)

?1.

Measure the voltage between test points 1 and 2.

Test condition	IG LOCK (0) or OFF mode
Test circuit	HORN SW
Test point 1	Under-dash fuse/relay box connector H (13P) No. 10 (LT BLU)
Test point 2	Body ground

Is there battery voltage?


	YES

Go to step 8.


	YES

Go to step 10.


	NO

Faulty MICU; replace the under-dash fuse/relay box.?

Open wire check (HORN SW line) 1:

Open wire check (HORN SW line) 1

?1.	Remove the driver's airbag assembly.

?2.

Measure the voltage between test points 1 and 2.

Test condition	IG LOCK (0) or OFF mode
Test circuit	HORN SW
Test point 1	Cable reel connector A (20P) No. 9 (LT BLU)
Test point 2	Body ground

Is there battery voltage?


	YES

Go to step 9.


	NO

Repair an open or high resistance in the wire.?

Cable reel check:

Cable reel check

?1.

Measure the voltage between test points 1 and 2.

Test condition	IG LOCK (0) or OFF mode
Test circuit	HORN SW
Test point 1	Cable reel connector C (20P) No. 2 (ORN)
Test point 2	Body ground

Is there battery voltage?


	YES

Go to step 12.


	NO

Replace the cable reel.?

10.

Open wire check (HORN SW line) 1:

Open wire check (HORN SW line) 1

?1.	Remove the driver's airbag assembly.

?2.

Measure the voltage between test points 1 and 2.

Test condition	IG LOCK (0) or OFF mode
Test circuit	HORN SW
Test point 1	Cable reel connector A (20P) No. 2 (LT BLU)
Test point 2	Body ground

Is there battery voltage?


	YES

Go to step 11.


	NO

Repair an open or high resistance in the wire.?

11.

Cable reel check:

Cable reel check

?1.

Measure the voltage between test points 1 and 2.

Test condition	IG LOCK (0) or OFF mode
Test circuit	HORN SW
Test point 1	Cable reel connector C (20P) No. 14 (ORN)
Test point 2	Body ground

Is there battery voltage?


	YES

Go to step 12.


	NO

Replace the cable reel.?

12.

Open wire check (HORN SW line) 2:

Open wire check (HORN SW line) 2

?1.

Measure the voltage between test points 1 and 2.

Test condition	OFF mode
Test circuit	HORN SW
Test point 1	Horn switch 1P connector No. 1 (ORN)
Test point 2	Body ground

Is there battery voltage?


	YES

Check the installation of the driver's airbag assembly and the steering wheel. If the horn switch plate is OK, replace the driver's airbag assembly.?


	NO

Repair an open or high resistance in the wire.?

13.

Open wire check (HORN RLY OUT line):

Open wire check (HORN RLY OUT line)

?1.

Measure the voltage between test points 1 and 2.

Test condition	IG LOCK (0) or OFF mode Horn relay: disconnected Horn relay 4P socket No. 1 (RED) and No. 2 (BLU): jumped
Test circuit	HORN RLY OUT
Test point 1	Horn (LOW)/(HIGH) 1P connector No. 1 (BLU)
Test point 2	Body ground

Is there battery voltage?


	YES

Remove the horn, and test it. If the horn is OK, check the horn ground.?


	NO

Repair an open or high resistance in the wire.?