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."