[Previous][Next]
INSPECTION PROCEDURE 8: 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)
  • 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.-IIISE), check other system's DTC.
Check that the ETACS-ECU has not set a DTC.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ."
(2) Turn the ignition switch to the "ON" position.
(3) Check if DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
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: System 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: System 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.