Inspection Procedure 5: Horns do not sound while the security alarm system is triggered.


caution
  • Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.
  • When the ETACS-ECU of vehicles without KOS is replaced, the encrypted code of the ignition key needs to be registered to the ETACS-ECU. (If the encrypted code is not registered, the engine cannot be started. Register the encrypted code as described in Immobilizer System - How to Register Key ID .)

COMMENTS ON TROUBLE SYMPTOM


If horns do not sound, the horn input signal circuit or the ETACS-ECU may be defective.

PROBABLE CAUSES



DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code.


Check if diagnosis code is set to the ETACS-ECU.

Q. Is the diagnosis code set?
Diagnose the ETACS-ECU. Refer to GROUP 54A, Diagnosis .
Go to Step 2.

STEP 2. Horn relay check
Refer to .

Q. Is the check result normal?
Go to Step 3.
Replace the horn relay.

STEP 3. Voltage measurement at the horn relay connector
(1)Remove the relay, and measure at the relay box side.
(2)Measure the voltage between the horn relay connector (power supply terminal) and the body earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 5
Go to Step 4

STEP 4. Check of open circuit in power supply line between the fusible link and horn relay connector.

Q. Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.

STEP 5. Check of open circuit in N.HO line between the horn relay connector and ETACS-ECU connector.

Q. Is the check result normal?
Go to Step 6.
Repair the connector(s) or wiring harness.

STEP 6. Check of open circuit in power supply line between the horn (HI) or (LO) connector and horn relay connector.

Q. Is the check result normal?
Go to Step 7.
Repair the connector(s) or wiring harness.

STEP 7. Horn (HI) or (LO) check

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

Q. Is the check result normal?

Go to Step 8.

Replace the horn (HI) or (LO). go to step 8.

STEP 8. Retest the security alarm system.

Q. Does the theft-alarm system work normally?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Replace the ETACS-ECU.