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Inspection Procedure 12: The rear window defogger switch signal is not received. <vehicles with automatic 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 auto A/C controller assembly (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. Using scan tool (M.U.T.-III), check other systems 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 A/C-ECU system data list.
  • Operate the rear window defogger switch.
 
Item No.Item nameNormal condition
60Rear defogger switchOFF to ON (only when switch is operated)
Is the check result normal?
Go to Step 2.
Replace the auto A/C controller assembly.
 
STEP 2. Check of short to power supply, short to ground, and open circuit in DFSW line between ETACS-ECU connector and auto A/C controller assembly (A/C-ECU) connector.
Is the check result normal?
Go to Step 3.
Repair the connector(s) or wiring harness.
 
STEP 3. Using scan tool (M.U.T.-III), check data list.
Check the ETACS-ECU system data list.
  • 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.