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Rear window defogger does not operate.
 
 
 
 
 
 
TECHNICAL DESCRIPTION (COMMENT)
The rear window defogger is able to turn on while engine is running. If the defogger does not operate when the rear window defogger switch is turned on, the rear window defogger relay system may be defective.
 
 
 
TROUBLESHOOTING HINTS
  • The A/C control panel may be defective.
  • The rear window defogger relay may be defective.
  • The ETACS-ECU may be defective.
  • Damaged harness wires or connectors
 
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Using scan tool MB991958, diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
Connect scan tool MB991958. Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).
 
STEP 2. Check the A/C and outside/inside air selection damper control motor operation.
(1) Turn the ignition switch to the "ON" position.
(2) Check the engine running.
(3) Check the operations of outside/inside air selection damper control motor and A/C.
Do the A/C and outside/inside air selection damper control motor work normally?
Go to Step 3.
Refer to GROUP 55A - Inspection procedure 2, "Malfunction of the A/C control panel power supply system ."
 
STEP 3. Using scan tool MB991958, read the A/C control panel diagnostic trouble code.
Check that the A/C control panel has not set a DTC.
Is the DTC set?
Carry out the DTC procedures. Refer to GROUP 55A - Diagnosis .
Go to Step 4.
 
STEP 4. Using scan tool MB991958, read the ETACS-ECU diagnostic trouble code.
Check that the ETACS-ECU has not set a DTC.
Is the DTC set?
Carry out the DTC procedures. Refer to .
Go to Step 5.
 
STEP 5. Using scan tool MB991958, check data list.
Use the A/C control panel data list to check the signals related to the rear window defogger switch.
  • Start the engine.
  • Turn the rear window defogger switch from off to on.
 
Item No.Item nameNormal conditions
Item 60Rear defogger switchOFF → ON
Does scan tool MB991958 display the items "ON", and "OFF" as normal condition?
Go to Step 6
Replace the A/C control panel.
 
STEP 6. Check rear window defogger relay connector C-405 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Is rear window defogger relay connector C-405 in good condition?
Go to Step 7.
Repair or replace the connector. Refer to GROUP 00E, Harness Connector Inspection . The rear window defogger system should work normally.
 
STEP 7. Check the rear window defogger relay continuity.
Follow the table below to check the rear window defogger relay for continuity.
 
Battery voltageTerminal numberNormal condition
With no current applied3 - 4No continuity
With current applied [terminal 1 (-), terminal 2 (+)]Continuity exists (Less than 2 ohms)
Is the rear window defogger relay in good condition?
Go to Step 8.
Replace the rear window defogger relay. The rear window defogger system should work normally.
 
STEP 8. Check rear window defogger connector G-22 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Are rear window defogger connector G-22 in good condition?
Go to Step 9.
Repair or replace the connector. Refer to GROUP 00E, Harness Connector Inspection . The rear window defogger system should work normally.
 
STEP 9. Measure the voltage at rear window defogger connector G-22.
(1) Disconnect rear window defogger connector G-22, and measure the voltage at the harness side.
(2) Start the engine.
(3) Rear window defogger switch: ON (measure within 20 minutes after the switch is turned on)
(4) Measure the voltage between rear window defogger connector G-22 terminal No.1 and ground.
  • The measured value should be approximately 12 volts (battery positive voltage).
Is the measured voltage approximately 12 volts?
Go to Step 10.
Go to Step 11.
 
STEP 10. Measure the resistance at rear window defogger connector G-03.
(1) Disconnect rear window defogger connector G-03, and measure at the wiring harness side.
(2) Measure the resistance between terminal 1 and ground.
  • The measured value should be 2 Ω or less.
Does the measured resistance value correspond with this range?
Go to Step 18.
Repair the wiring harness. Check that the rear window defogger system works normally.
 
STEP 11. Measure the voltage at rear window defogger relay connector C-405.
(1) Disconnect rear window defogger relay connector C-405, and measure the voltage at the junction block side.
(2) Measure the voltage between terminal 4 and ground.
  • The measured value should be approximately 12 volts (battery positive voltage).
Is the measured voltage approximately 12 volts?
Go to Step 13.
Go to Step 12.
 
STEP 12. Check the wiring harness between rear window defogger relay connector C-405 (terminal 4) and the fusible link (37).
noteAlso check intermediate connector C-129 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-129 is damaged, repair or replace the connector as described in GROUP 00E, Harness Connector Inspection .
Is the wiring harness between rear window defogger relay connector C-405 (terminal 4) and the fusible link (37) in good condition?
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
Repair the wiring harness. Check that the rear window defogger system works normally.
 
STEP 13. Measure the voltage at rear window defogger relay connector C-405.
(1) Disconnect rear window defogger relay connector C-405, and measure the voltage at the junction block side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 2 and ground.
  • The measured value should be approximately 12 volts (battery positive voltage).
Is the measured voltage approximately 12 volts?
Go to Step 14.
Go to Step 16.
 
STEP 14. Check ETACS-ECU connector C-411 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Is ETACS-ECU connector C-411 in good condition?
Go to Step 15.
Repair or replace the connector. Refer to GROUP 00E, Harness Connector Inspection . Check that the rear window defogger system works normally.
 
STEP 15. Check the wiring harness between rear window defogger relay connector C-405 (terminal 1) and ETACS-ECU C-411 (terminal 12).
Is the wiring harness between rear window defogger relay connector C-405 (terminal 1) and ETACS-ECU connector C-411 (terminal 12) in good condition?
Replace the ETACS-ECU.
Repair the wiring harness. Check that the rear window defogger system works normally.
 
STEP 16. Check the wiring harness between rear window defogger relay connector C-405 (terminal 2) and ETACS-ECU connector C-417 (terminal 5).
  • Check the wiring harness for open circuit and short circuit.
noteAlso check joint connector C-04 for loose, corroded, or damaged terminal, or terminal pushed back in the connector. If joint connector C-04 is damaged, repair or replace the connector as described in GROUP 00E, Harness Connector Inspection .
Is the wiring harness between rear window defogger relay connector C-405 (terminal 2) and ETACS-ECU connector C-417 (terminal 5) in good condition?
Go to Step 17.
Repair or replace the wiring harness. Refer to GROUP 00E, Harness Connector Inspection . Check that the rear window defogger system works normally.
 
STEP 17. Check the wiring harness between rear window defogger relay connector C-405 (terminal 3) and rear window defogger connector G-22 (terminal 1).
noteAlso check intermediate connectors C-26 and G-23 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connectors C-26 and G-23 is damaged, repair or replace the connector as described in GROUP 00E, Harness Connector Inspection .
Is the wiring harness between rear window defogger relay connector C-405 (terminal 3) and rear window defogger connector G-22 (terminal 1) in good condition?
Replace the ETACS-ECU.
Repair or replace the wiring harness. Refer to GROUP 00E, Harness Connector Inspection . Check that the rear window defogger system works normally.
 
STEP 18. Check A/C control panel connector C-216 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Is A/C-ECU connector C-210 in good condition?
Go to Step 19.
Repair or replace the connector. Refer to GROUP 00E, Harness Connector Inspection . Check that the rear window defogger system works normally.
 
STEP 19. Check the wiring harness between rear window defogger relay connector C-405 (terminal 2) and A/C control panel connector C-216 (terminal 20).
  • Check the wiring harness for open circuit and short circuit.
noteAlso check joint connector C-04 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-04 is damaged, repair or replace the connector as described in GROUP 00E, Harness Connector Inspection .
Are the wiring harness between rear window defogger relay connector C-405 (terminal 2) and A/C control panel connector C-216 (terminal 20) in good condition?
Go to Step 20.
Repair or replace the wiring harness. Refer to GROUP 00E, Harness Connector Inspection . Check that the rear window defogger system works normally.
 
STEP 20. Check the rear window defogger.
(1) Let the engine run at 2,000 r/min, and check the printed heater with the battery fully charged.
(2) Turn on the rear window defogger switch, and use a voltmeter to measure the voltage in each printed heater at middle point A on the rear window glass.
  • The value should be approximately 6 volts.
Does the rear window defogger work normally?
Return to Step 1.
Replace the rear window defogger.