Inspection Procedure J-1

Taillight Relay Drive Circuit:

CIRCUIT OPERATION
The front-ECU illuminates the taillights if the column switch sends the taillight ON signal to the front-ECU.

TECHNICAL DESCRIPTION (COMMENT)
The taillight relay, the column switch or the front-ECU may be defective.

NOTE: If only one light does not illuminate, the harness wire between the light and the taillight relay may be defective or the light bulb may be burned out. In this case, check the circuit by referring to Taillight, Position Light and License Plate Light.

TROUBLESHOOTING HINTS
- Malfunction of the taillight relay
- Malfunction of the column switch (turn-signal light and lighting switch)
- Malfunction of the front-ECU
- Damaged harness wires or connectors

DIAGNOSIS
Required Special Tools:
MB991223: Test Harness Set
MB991502: Scan Tool (MUT-II)
MB991529: Diagnostic Trouble Code Check Harness

STEP 1. Check the DTC.
If the DTC sets when the ignition switch is turned to "LOCK" (OFF) position, carry out the troubleshooting by referring to Diagnostic Trouble Code Chart. If the DTC does not set, go to Step 2.

STEP 2. Check the input signal.
Check the input signal from the taillight switch.






CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.

1. Connect scan tool MB991502 to the data link connector.
2. Check that the tone alarm of scan tool MB991502 sounds when the input signal enters.





1. Use special tool MB991529 to connect a voltmeter between ground terminal 4 or 5 and ETACS-ECU terminal 9 of the data link connector.
2. Check that the voltmeter indicator deflects once when the input signal enters.
If a defect appears, check the taillight switch input circuit. Refer to Inspection Procedure O-17.
If no defect appears, go to Step 3.







STEP 3. Check the taillight relay.
If the taillight relay is damaged, replace it. The taillight should illuminate.
If the taillight relay is not damaged, go to Step 4.




STEP 4. Check the taillight relay power supply circuit at the taillight relay connector A-05X.
1. Disconnect the taillight relay connector A-05X and measure at the relay box side.
2. Voltage between terminal 4 and ground.
- Voltage should be approximately 12 volts (battery positive voltage).

3. Voltage between terminal 3 and ground.
- Voltage should be approximately 12 volts (battery positive voltage).
If one of the measurements above does not show approximately 12 volts, go to Step 5.
If both of the measurements above show approximately 12 volts, go to Step 7.




STEP 5. Check the taillight relay connector A-05X for damage.
If the taillight relay connector A-05X is damaged, repair or replace it. Refer to Harness Connector Inspection.
The taillights should illuminate.
If the connector is in good condition, go to Step 6.




STEP 6. Check the harness wire between taillight relay connector A-05X and battery.
If the harness wire between taillight relay connector A-05X and battery is damaged, repair it.
The taillights should illuminate.




STEP 7. Check the taillight relay connector A-05X and front-ECU connector A-09X for damage.
If the taillight relay connector A-05X and front-ECU connector A-09X are damaged, repair or replace them. Refer to Harness Connector Inspection.
The taillights should illuminate.
If the connectors are in good condition, go to Step 8.




STEP 8. Check the harness wire between taillight relay connector A-05X and front-ECU connector A-09X.
If the harness wire between taillight relay connector A-05X and front-ECU connector A-09X is damaged, repair it. The taillights should illuminate.

If the harness wire is in good condition, replace the front-ECU. The taillights should illuminate.