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INSPECTION PROCEDURE 11: A/C controller assembly (A/C-ECU) power supply system
 
 
 
 
TECHNICAL DESCRIPTION (COMMENT)
If the A/C controller assembly (A/C-ECU) is not energized, the power supply or ground system to the ECU may be defective.
 
 
 
TROUBLESHOOTING HINT
  • Malfunction of the A/C controller assembly (A/C-ECU)
  • Damaged wiring harness or connectors
 
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Using scan tool (M.U.T.-IIISE), check other system's DTC.
Check that the ETACS-ECU has not set a DTC.
Is the DTC set?
Carry out the DTC procedures. Refer to GROUP 54A, ETACS-ECU .
Go to Step 2.
 
STEP 2. Measure the voltage at the A/C controller assembly (A/C-ECU) connector.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Ignition switch: "ON"
(3) Voltage between IG1 terminal and body ground
OK: The voltage should measure approximately 12 volts (battery positive voltage)
Is the check result normal?
Go to Step 4.
Go to Step 3.
 
STEP 3. Check of open circuit in IG1 line between ETACS-ECU connector and A/C controller assembly (A/C-ECU) connector.
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 4. Measure the voltage at the A/C controller assembly (A/C-ECU) connector.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Voltage between B/UP terminal and body ground
OK: The voltage should measure approximately 12 volts (battery positive voltage)
Is the check result normal?
Go to Step 6.
Go to Step 5.
 
STEP 5. Check of open circuit in B/UP line between ETACS-ECU connector and A/C controller assembly (A/C-ECU) connector.
notePrior to the wiring harness inspection, check joint connector and repair if necessary.
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 6. Measure the resistance at the A/C controller assembly (A/C-ECU) connector.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Resistance between E terminal and body ground
OK: Continuity exists (2 Ω or less)
Is the check result normal?
Replace the A/C controller assembly (A/C-ECU).
Go to Step 7.
 
STEP 7. Check of open circuit in E line between A/C controller assembly (A/C-ECU) connector and body ground.
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.