The rear window
defogger does not work. <vehicles with automatic air conditioner>
COMMENTS ON TROUBLE SYMPTOM
If the rear window defogger does not work after switching on (the defogger timer will
be on for approximately 20 minutes), the rear window defogger relay circuit may be defective.
PROBABLE CAUSES
- Malfunction of CAN bas line
- Wiring harness or connector failure
- Malfunction of A/C-ECU
- Malfunction of ETACS-ECU
- Malfunction of the rear window defogger relay
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 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 3.
STEP 3. M.U.T.-III other system’s diagnosis code
Check that the engine-ECU has not set a diagnosis code.
Q.
Is the diagnosis code set?
Troubleshoot the engine (Refer to GROUP 13B - Troubleshooting, Diagnosis
Code Chart <6B3> or GROUP 13C - Troubleshooting,
Diagnosis Code Chart <4N1>.)
Go to Step 4.
STEP 4. M.U.T.-III data list
Check the A/C-ECU system data list.
- Turn the rear window defogger switch from off to on.
Item No.
|
Item name
|
Normal condition
|
60
|
Rear defogger switch
|
OFF to ON (only when switch is operated)
|
Q.
Is the check result normal?
Go to Step 5.
Replace the auto A/C controller assembly (Refer to group 55B - Heater
Control Unit ).
STEP 5. Check the rear window defogger relay.
Refer to .
Q.
Is the check result normal?
Go to Step 6.
Replace the defogger relay.
STEP 6. Voltage measurement at the rear window defogger connector.
|
|
(1)Disconnect the connector, and measure at the wiring harness side.
|
|
|
(3)Rear window defogger switch: ON.
|
|
|
(4)Measure the voltage between the rear window defogger connector (power supply terminal)
and the body earth.
OK: System voltage
|
Q.
Is the check result normal?
Go to Step 7.
Go to Step 8.
STEP 7. Resistance measurement at the rear window defogger connector.
|
|
(1)Disconnect the connector, and measure at the wiring harness side.
|
|
|
(2)Measure the resistance between the rear window defogger connector (earth terminal)
and the body earth.
OK: Continuity exists (2 Ω or less)
|
Q.
Is the check result normal?
Go to Step 14.
Repair the glass antenna choke coil <glass antenna>, connector(s) or wiring
harness wires between rear window defogger connector terminal and body earth.
STEP 8. Voltage measurement at the rear window defogger relay connector.
|
|
(1)Remove the relay, and measure at the junction block side.
|
|
|
(2)Measure the voltage between the rear window defogger relay connector (power supply
terminal) and the 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, and open circuit in power
supply line between rear window defogger relay connector and fusible link.
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, and open circuit in output
line between rear window defogger relay connector and rear window defogger connector.
Q.
Is the check result normal?
Go to Step 11.
Repair the glass antenna choke coil <glass antenna>, connector(s) or wiring
harness wires between rear window defogger relay connector terminal and rear window defogger
connector.
STEP 11. Voltage measurement at the rear window defogger relay connector.
|
|
(1)Remove the relay, and measure at the junction block side.
|
|
|
(3)Measure the voltage between the rear window defogger relay connector (input terminal)
and the body earth.
OK: System voltage
|
Q.
Is the check result normal?
Go to Step 13.
Go to Step 12.
STEP 12. Check of short to power supply, and open circuit in input
line between rear window defogger relay connector and ignition switch (IG2).
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 13. Check of short to power supply, and open circuit in DEF1
line between rear window defogger relay connector and ETACS-ECU connector.
Q.
Is the check result normal?
Go to Step 14.
Repair the connector(s) or wiring harness.
STEP 14. Check the rear window defogger.
Check the rear window defogger (Refer to ).
Q.
Is the check result normal?
Return to Step 1.
Replace the rear window glass (Refer to GROUP 42A - Tailgate Window Glass ).