Inspection Procedure O-3

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

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

TECHNICAL DESCRIPTION (COMMENT)
If the horns do not sound when the theft-alarm system is triggered, 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 answerback and horn answerback function.

Q: Does the keyless entry hazard answerback and horn answerback function work normally?

YES : Replace the ETACS-ECU. When the ETACS-ECU is replaced, register the encrypted code. 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 answerback function." Inspection Procedure E-2