Inspection Procedure 3

INSPECTION PROCEDURE 3: Theft-Alarm Horn Does Not Sound While The Theft-Alarm System Is Triggered.

CAUTION: Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.

Theft-alarm Horn Circuit:

TECHNICAL DESCRIPTION (COMMENT)
If theft-horn does not sound, the theft-horn input signal circuit or the ETACS-ECU may be defective. Also, the theft-alarm function and horn may have been disabled with a configuration function.

TROUBLESHOOTING HINTS
- Theft-alarm horn may be defective
- Theft-alarm 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:
- MB992006: Extra fine probe
- MB991223: Harness set
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool MB991958, read the diagnostic trouble code.

Check if DTC is set to the ETACS-ECU.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.







1. Connect scan tool MB991958. Refer to "How to connect scan tool (M.U.T.-III)." How to Connect the Scan Tool (M.U.T.-III)
2. Turn the ignition switch to the "ON" position.
3. Check whether the ETACS-ECU related DTC is set
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES : Diagnose the ETACS-ECU. Diagnostic Trouble Code Descriptions

NO : Go to Step 2.

STEP 2. Check the theft-alarm horn work normally.







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

Q: Is the check result normal?

YES : Go to Step 3.

NO : Replace the theft-alarm horn. go to Step 3.

STEP 3. Check theft-alarm horn connector A-59 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is theft-alarm horn connector A-59 in good condition?

YES : Go to Step 4.

NO : Repair the damaged parts.

STEP 4. Check theft-alarm horn relay connector A-18X for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is theft-alarm horn relay connector A-18X in good condition?

YES : Go to Step 5.

NO : Repair the damaged parts.

STEP 5. Check the theft-alarm horn relay.

Refer to Theft-alarm Indicator Check. Component Tests and General Diagnostics

Q: Is the theft-alarm horn relay in good condition

YES : Go to Step 6.

NO : Replace the theft-alarm horn relay.

STEP 6. Measure the voltage at theft-alarm horn relay A-18X.

1. Remove the relay, and measure at the relay box side







2. Measure the voltage between theft-alarm horn relay connector A-18X (terminal No. 1,4) and the body ground.
- The voltage should measure approximately 12 volts (battery positive voltage).

Q: Is the measured voltage approximately 12 volts (battery positive voltage)?

YES : Go to Step 8.

NO : Go to Step 7.

STEP 7. Check the Wiring harness between theft-alarm horn relay connector A-18X (terminal No. 1,4) and fusible link (36).

Check the power supply line for open circuit and short circuit.

Q: Is the check result normal?

YES : The trouble can be an intermittent malfunction.

NO : Repair the wiring harness between theft-alarm horn relay connector A-18X and fusible link (36).

STEP 8. Check theft-alarm horn connector A-59 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is theft-alarm horn connector A-59 in good condition?

YES : Go to Step 9.

NO : Repair the damaged parts.

STEP 9. Check the Wiring harness between theft-alarm horn connector A-59 (terminal No. 1) and theft-alarm horn relay connector A-18X (terminal No. 3).

Check the output lines for open circuit and short circuit.

NOTE: Before the wiring harness check, check intermediate connector A-04, and then repair them if necessary.

Q: Is the check result normal?

YES : Go to Step 10.

NO : Repair the wiring harness between theft-alarm horn connector A-59 and theft-alarm horn relay connector A-18X.

STEP 10. Check ETACS-ECU connector C-312 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is ETACS-ECU connector C-312 in good condition?

YES : Go to Step 11.

NO : Repair the damaged parts.

STEP 11. Check the Wiring harness between theft-alarm horn relay connector A-18X (terminal No. 2) and ETACS-ECU connector C-312 (terminal No. 15).

Check the output lines for open circuit and short circuit.

Q: Is the check result normal?

YES : Go to Step 12.

NO : Repair the wiring harness between theft-alarm horn relay connector A-18X and ETACS-ECU connector C-312.

STEP 12. Retest the system.

Q: Does the theft-alarm work normally?

YES : he trouble can be an intermittent malfunction.

NO : Replace the ETACS-ECU.