The rear window defogger does not work.



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


The rear window defogger relay may be defective when the rear window defogger cannot be activated although the rear window defogger switch is turned on (the 20-minute timer initiates) or ambient temperature is low (the rear window defogger has never been activated since the ignition switch is turned ON) with "Auto Rear Defogger (Engine Start)" enabled by using the customisation function of the ETACS-ECU.
note When the engine is not running, the rear window defogger does not work.

PROBABLE CAUSES




DIAGNOSIS PROCEDURE


STEP 1. M.U.T.-III CAN bus diagnostics


Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

Go to Step 2

Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ).

STEP 2. M.U.T.-III diagnosis code


Check that the air conditioner has not set a diagnosis code.

Q. Is the diagnosis code set?

Carry out the diagnosis code procedures. (Refer to GROUP 55-trouble shooting .)

Go to Step 3

STEP 3. M.U.T.-III other system’s diagnosis code


Check that the ETACS-ECU has not set a diagnosis code.

Q. Is the diagnosis code set?

Carry out the diagnosis code procedures. Refer to .

Go to Step 4

STEP 4. M.U.T.-III data list


Check the rear window defogger switch signal by the data list of the A/C-ECU.

Item No.
Item name
Normal condition
Item 60
Rear defogger switch
OFF → ON

Q. Is the check result normal?

Go to Step 5

Refer to GROUP 55 - Inspection Procedure 12 "Heater controller assembly (A/C-ECU) power supply system"

STEP 5. Voltage measurement at rear window defogger connector (power supply terminal).


(1)Disconnect the connector, and measure at the wiring harness side.
(2)Ignition switch: ON
(3)Rear window defogger switch must be turned on, or the operational conditions for the customisation function "Auto Rear Defogger (Engine Start)" must be satisfied (measure within 20 minutes after the switch is turned on).
(4)Check the voltage between the rear window defogger connector (power supply terminal) and body earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 6

Go to Step 8

STEP 6. Resistance measurement at rear window defogger connector (earth terminal).


(1)Disconnect the connector, and measure at the wiring harness side.
(2)Measure the resistance between the rear window defogger connector (earth terminal) and body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Go to Step 11

Go to Step 7

STEP 7. Check of open circuit in earth line between rear window defogger connector and body earth.


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 8. Voltage measurement at ETACS-ECU connector (+B2 terminal).


(1)Disconnect the connector, and measure at the wiring harness side.
(2)Check the voltage between the ETACS-ECU connector (+B2 terminal) and body earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 10

Go to Step 9

STEP 9. Check of short to power supply, short to earth, and open circuit in +B2 line between fusible link and ETACS-ECU connector.


Q. Is the check result normal?

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 10. Check of short to power supply, short to earth, and open circuit in DEFL line between ETACS-ECU connector and rear window defogger connector.


Q. Is the check result normal?

Go to Step 11

Repair the connector(s) or wiring harness.

STEP 11. Check the rear window defogger.


Check the rear window defogger (Refer to ).

Q. Is the check result normal?

Go to Step 12

Replace the rear window glass, and then go to Step 12.

STEP 12. Check the rear window defogger.


Check the rear window defogger (Refer to ).

Q. Is the check result normal?

Return to Step 1.

Replace the ETACS-ECU.