Inspection Procedure N-2

Theft-alarm System: Horn does not Sound when the Theft-alarm is Triggered.

Theft-alarm Horn Drive Circuit:

Horn Drive Circuit Part 1:

Horn Drive Circuit Part 2:

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

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

DIAGNOSIS

Required Special Tool:
- MB991223: Test Harness Set

STEP 1. Check which horn is defective.

Check which horn does not sound when the theft-alarm system is triggered.

Q: Which horn does not sound?

theft-alarm horn: Go to Step 2.

horn: Go to Step 12.

theft-alarm horn and all vehicle horns: Replace the ETACS-ECU. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

STEP 2. Check the theft-alarm horn.




1. Remove the horn.




2. Connect the battery as shown, and check that the theft-alarm horn sounds.

Q: Does the theft-alarm horn sound?

YES: Go to Step 3.

NO: Replace the theft-alarm horn. All the vehicle horn (including the theft-alarm 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 normal?

YES: Go to Step 4.

NO: Replace the theft-alarm horn relay. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

STEP 4. Measure at theft-alarm horn relay connector A-06X in order to check the fusible link (4) line of the power supply system to the theft-alarm horn relay.




1. Disconnect theft-alarm horn relay connector A-06X, and measure at the relay box side.




2. Measure the voltage between terminal 1, 2 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q: Does the measured voltage correspond with this range?

YES: Go to Step 7.

NO: Go to Step 5.




STEP 5. Check theft-alarm horn relay connector A-06X for damage.

Q: Is theft-alarm horn relay connector A-06X in good condition?

YES: Go to Step 6.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.




STEP 6. Check the wiring harness between theft-alarm horn relay connector A-06X (terminals 1 and 2) and fusible link (4).

Q: Is the wiring harness between theft-alarm horn relay connector A-06X (terminals 1 and 2) and fusible link 4. in good condition?

YES: Replace the ETACS-ECU. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

NO: Repair the wiring harness. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.




STEP 7. Check theft-alarm horn relay connector A-06X and theft-alarm horn connector A-25 for damage.

Q: Are theft-alarm horn relay connector A-06X and theft-alarm horn connector A-25 in good condition?

YES: Go to Step 8.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.







STEP 8. Check the wiring harness between theft-alarm horn relay connector A-06X (terminal 4) and theft-alarm horn connector A-25 (terminal 1).

Q: Is the wiring harness between horn relay connector A-06X (terminal 4) and theft-alarm horn connector A-25 (terminal 1) in good condition?

YES: Go to Step 9.

NO: Repair the wiring harness. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.







STEP 9. Check theft-alarm horn relay connector A-06X and ETACS-ECU connector C-117 for damage.

Q: Are theft-alarm horn relay connector A-06X and ETACS-ECU connector C-117 in good condition?

YES: Go to Step 10.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.



















STEP 10. Check the wiring harness between theft-alarm horn relay connector A-06X (terminal 3) and ETACS-ECU connector C-117 (terminal 40).

NOTE: Also check intermediate connector C-89. If intermediate connector C-89 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between theft-alarm horn relay connector A-06X (terminal 3) and ETACS-ECU connector C-117 (terminal 40) in good condition?

YES: Go to Step 11.

NO: Repair the wiring harness. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

STEP 11. Check the fit of the theft-alarm horn.

NOTE: The theft-alarm horn is grounded to the vehicle body via its mounting bolt.

Q: Is the theft-alarm horn installed correctly?

YES: Replace the ETACS-ECU. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

NO: Install the theft-alarm horn correctly. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.







STEP 12. Check the horn relay.

Q: Is the horn relay normal?

YES: Go to Step 13.

NO: Replace the horn relay. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

STEP 13. Measure at horn relay connector A-05X in order to check the battery power supply system to the horn relay.




1. Disconnect horn relay connector A-05X, and measure at the relay box side.




2. Measure the voltage between terminal 1, 2 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q: Does the measured voltage correspond with this range?

YES: Go to Step 16.

NO: Go to Step 14.




STEP 14. Check horn relay connector A-05X for damage.

Q: Is horn relay connector A-05X in good condition?

YES: Go to Step 15.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.




STEP 15. Check the wiring harness between horn relay connector A-05X (terminals 1 and 2) and the battery.

Q: Is the wiring harness between horn relay connector A-05X (terminals 1 and 2) and the battery in good condition?

YES: Replace the ETACS-ECU. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

NO: Repair the wiring harness. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.







STEP 16. Check horn relay connector A-05X and horn connector A-27 for damage.

Q: Are horn relay connector A-05X and horn connector A-27 in good condition?

YES: Go to Step 17.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.







STEP 17. Check the wiring harness between horn relay connector A-05X (terminal 4) and horn connector A-27 (terminal 1).

Q: Is the wiring harness between horn relay connector A-05X (terminal 4) and horn connector A-27 (terminal 1) in good condition?

YES: Go to Step 18.

NO: Repair the wiring harness. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.







STEP 18. Check rear horn relay connector A-05X and ETACS-ECU connector C-117 for damage.

Q: Are horn relay connector A-05X and ETACS-ECU connector C-117 in good condition?

YES: Go to Step 19.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.










STEP 19. Check the wiring harness between horn relay connector A-05X (terminal 3) and ETACS-ECU connector C-117 (terminal 44).

NOTE: Also check intermediate connector C-89. If intermediate connector C-89 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between horn relay connector A-05X (terminal 3) and ETACS-ECU connector C-117 (terminal 44) in good condition?

YES: Replace the ETACS-ECU. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

NO: Repair the wiring harness. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

STEP 20. Check the horn.




1. Remove the horn.




2. Connect the battery as shown, and check that the horn sounds.

Q: Is the horn normal?

YES: Go to Step 21.

NO: Replace the horn. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

STEP 21. Check the fit of the horn.
Check that the horn is installed correctly.

NOTE: The horn is grounded to the vehicle body via its mounting bolt.

Q: Is the horn installed correctly?

YES: Replace the ETACS-ECU. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.

NO: Install the horn correctly. All the vehicle horn (including the theft-alarm horn) should sound when the theft-alarm system is triggered.