Inspection Procedure M-2

M-2: Theft-Alarm System: Horn Does Not Sound When the Theft-Alarm Is Triggered.

Theft-alarm Horn Circuit:

Connectors:

CIRCUIT OPERATION
The ETACS-ECU will sound the theft-alarm horn and horn if the theft-alarm system or the keyless entry system answerback is triggered.

TECHNICAL DESCRIPTION (COMMENT)
The theft-alarm horn is shared by the keyless entry system. If the theft-alarm horn sounds normally through the keyless entry system answerback, the ETACS-ECU may be defective.

TROUBLESHOOTING HINTS
- Malfunction of the theft-alarm horn
- Malfunction of the theft-alarm horn relay
- Malfunction of the ETACS-ECU
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tool:
- MB991223: Test Harness Set

STEP 1. Check the keyless entry system horn answerback.
Activate the keyless entry system horn answerback. (Refer to Keyless Entry System - Enabling/disabling the Answerback Function.)

Q: Does the horn answerback function work?

YES: Replace the ETACS-ECU. The horn should sound when the theft-alarm system is triggered.

NO: Go to Step 2.




STEP 2. Check the theft-alarm horn. Connect the battery as shown and check that the theft-alarm horn sounds.
Q: Is the theft-alarm horn in good condition?

YES: Go to Step 3.

NO: Replace it. The horn should sound when the theft-alarm system is triggered.




STEP 3. Check the theft-alarm horn relay.
Q: Is the theft-alarm horn relay in good condition?

YES: Go to Step 4.

NO: Replace it. The horn should sound when the theft-alarm system is triggered.

STEP 4. Check the theft-alarm horn relay power supply circuit at the theft-alarm horn relay connector A-11X.
1. Disconnect the theft-alarm horn relay connector A-11X and measure at the relay box side.




2. Measure the voltages between terminals 3, 5 and ground.

Q: Are the voltages approximately 12 volts (battery positive voltage)?

YES: Go to Step 7.

NO: Go to Step 5.




STEP 5. Check the theft-alarm horn relay connector A-11X for damage.
Q: Is theft-alarm horn relay connector A-11X in good condition?

YES: Go to Step 6.

NO: Repair or replace it. Refer to Harness Connector Inspection. The horn should sound when the theft-alarm system is triggered.
















STEP 6. Check the harness wires between theft-alarm horn relay connector A-11X and fusible link (1).

NOTE: After checking intermediate connector C-66 and junction block connector C-77 and C-85, check the wires. If intermediate connector C-66 and junction block connector C-77 and C-85 are damaged, repair or replace them. Refer to Harness Connector Inspection.

Q: Are the harness wire between theft-alarm horn relay connector A-11X and fusible link (1) in good condition?

YES: There is no action to be taken.

NO: Repair them. The horn should sound when the theft-alarm system is triggered.







STEP 7. Check the theft-alarm horn relay connector A-11X and ETACS-ECU connector C-81 for damage.
Q: Are theft-alarm horn relay connector A-11X and ETACS-ECU connector C-81 in good condition?

YES: Go to Step 8.

NO: Repair or replace them. Refer to Harness Connector Inspection. The horn should sound when the theft-alarm system is triggered.










STEP 8. Check the harness wires between theft-alarm horn relay connector A-11X and ETACS-ECU connector C-81.

NOTE: After checking intermediate connector C-66, check the wires. If intermediate connector C-66 is damaged, repair or replace it. Refer to Harness Connector Inspection.

Q: Are the harness wires between theft-alarm horn relay connector A-11X and ETACS-ECU connector C-81 in good condition?

YES: Go to Step 9.

NO: Repair them. The horn should sound when the theft-alarm system is triggered.







STEP 9. Check the theft-alarm horn relay connector A-11X and theft-alarm horn connector A-23 for damage.
Q: Are theft-alarm horn relay connector A-11X and theft-alarm horn connector A-23 in good condition?

YES: Go to Step 10.

NO: Repair or replace them. Refer to Harness Connector Inspection. The horn should sound when the theft-alarm system is triggered.







STEP 10. Check the harness wire between theft-alarm horn relay connector A-11X and theft-alarm horn connector A-23.
Q: Is the harness wire between horn relay connector A-11X and theft-alarm horn connector A-23 in good condition?

YES: Go to Step 11.

NO: Repair it. The horn should sound when the theft-alarm system is triggered.

STEP 11. Check that the theft-alarm horn is installed properly.

NOTE: The theft-alarm horn is grounded to the body through the installation bolts.

Q: Is the theft-alarm horn installation in good condition?

YES: Replace the ETACS-ECU. The horn should sound when the theft-alarm system is triggered.

NO: Repair it. The horn should sound when the theft-alarm system is triggered.