Inspection Procedure O-3

INSPECTION PROCEDURE O-3: Theft-alarm System: Horn does not sound when the theft-alarm system is triggered.

CIRCUIT OPERATION

When the theft-alarm system is triggered, the ETACS-ECU sounds the all the vehicle horns.

TECHNICAL DESCRIPTION (COMMENT)

If the horns do not sound when the theft-alarm system is triggered, the horn, the horn relay and the ETACS-ECU may be defective.

TROUBLESHOOTING HINTS

- The horn may be defective
- The horn relay may be defective
- The ETACS-ECU may be defective
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector

DIAGNOSIS

Required Special Tools:

- MB991223: Harness Set
- MB992006: Extra Fine Probe

Verify the keyless entry hazard answer back and horn answer back function.

Q. Does the keyless entry hazard answer back and horn answer back function work normally?

YES Replace the ETACS-ECU. When the ETACS-ECU is replaced, register the encrypted code. Immobilizer System. The horns should sound when the theft-alarm system is triggered.
NO Refer to Inspection Procedure E-2 "The dome light, the turn-signal lights and the horn do not operate through the answer back function Inspection Procedure E-2."