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Inspection Procedure 1: Scan Tool (M.U.T.-IIISE) cannot Communicate with ACC System.
 
 
cautionWhen the ACC/FCM-ECU is replaced, calibrate the radar (refer to ).
 
 
COMMENTS ON TROUBLE SYMPTOM
When scan tool (M.U.T.-IIISE) cannot communicate with the ACC system, ACC/FCM-ECU power supply circuit system, ground, or ACC/FCM-ECU may be faulty.
 
 
PROBABLE CAUSES
  • Abnormality in power supply voltage to ACC/FCM-ECU
  • Damaged wiring harness and connectors
  • Malfunction of the ACC/FCM-ECU
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Measure the resistance at ACC/FCM-ECU connector.
(1) Check the connector
(2) Disconnect the connector.
(3) Measure the resistance between ACC/FCM-ECU connector terminal GND and body ground at the wiring harness side.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 2.
Repair the connector(s), or check and repair of open circuit, and damage in GND line between ACC/FCM-ECU connector and body ground.
 
STEP 2. Measure the terminal voltage at ACC/FCM-ECU connector.
(1) Check the connector
(2) Disconnect the connector.
(3) Turn the ignition switch to the "ON" position.
(4) Measure the terminal voltage between ACC/FCM-ECU connector terminal IG and body ground at the wiring harness side.
OK: The voltage should measure approximately 12 volts (battery positive voltage)
Is the check result normal?
Go to Step 3.
Repair the connector(s), or check and repair of short to ground, and open circuit in IG line between ACC/FCM-ECU connector and IG1 relay connector.
 
STEP 3. Check the symptom.
Can the scan tool (M.U.T.-IIISE) communicate with ACC system?
It can be assumed that this malfunction is intermittent (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunction ).
Replace the ACC/FCM-ECU (Refer to ).