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Inspection Procedure 11: The rear window defogger switch signal is not received. <vehicles with manual air conditioning>
 
 
cautionWhenever the ECU is replaced, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
 
 
TECHNICAL DESCRIPTION (COMMENT)
Input signal from the rear window defogger switch is used to operate the functions below. If the signal is abnormal, these functions will not work normally.
  • Rear window defogger
 
 
TROUBLESHOOTING HINTS
  • The heater control panel (rear window defogger switch) may be defective
  • The ETACS-ECU may be defective
  • The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Check the rear window defogger switch.
Refer to .
Is the check result normal?
Go to Step 2.
Replace the heater control panel.
 
STEP 2. Resistance measurement at heater control panel connector (ground terminal)
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the resistance between the heater control panel connector (ground terminal) and ground.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 4.
Go to Step 3.
 
STEP 3. Check of open circuit in ground line between heater control panel connector and ground
Is the check result normal?
Intermittent malfunction is suspected (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 4. Check of short to power supply, short to ground, and open circuit in DFSW line between ETACS-ECU connector and heater control panel connector
Is the check result normal?
Go to Step 5.
Repair the connector(s) or wiring harness.
 
STEP 5. Using scan tool (M.U.T.-III), check data list.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III). Refer to "How to connect Scan Tool (M.U.T.-III) ."
(2) Check the input signals from the rear window defogger switch
  • Operate the rear window defogger switch.
 
Item No.Item nameNormal condition
103Rear defogger switchOFF to ON (only when switch is operated)
OK: Normal condition is displayed.
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 ).
Replace the ETACS-ECU.