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Inspection Procedure 1: Scan tool cannot communicate with WCM.
 
 
cautionBefore replacing the ECU, ensure that the communication circuit is normal.
 
 
TECHNICAL DESCRIPTION (COMMENT)
If the scan tool cannot communicate with the WCM, the CAN bus lines may be defective. If the WCM does not work, the WCM or the power supply circuit may be defective.
 
 
TROUBLESHOOTING HINTS
  • Malfunction of the power supply or ground of WCM
  • Malfunction of CAN bus line
  • Malfunction of WCM
 
 
DIAGNOSIS
STEP 1. Using scan tool MB991958, diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
Connect scan tool MB991958. Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).
 
STEP 2. Check the power supply circuit and the ground circuit to WCM.
Refer to Inspection Procedure 4 "Abnormality in WCM power supply and ground circuits" .
Are the power supply circuit and the ground circuit to WCM in good condition ?
Go to Step 3.
Repair the power supply circuit and the ground circuit to WCM.
 
STEP 3. Retest the system
Check if scan tool MB991958 can communicate with WCM.
Does the scan tool MB991958 cannot communicate with WCM in good condition?
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 WCM and register the ID codes (Refer to ).