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Inspection Procedure 3: The steering has become heavy, but electric power steering warning symbol does not illuminate. (Power supply voltage assist fall)
 
 
 
 
COMMENTS ON TROUBLE SYMPTOM
Intermittent failure may be present in the power supply system. Check the battery and the generator to confirm that normal direct voltage flows.
 
 
 
PROBABLE CAUSES
  • Malfunction of CAN bus line
  • Defective battery
  • Charging system failed
  • Malfunction of the electric power steering-ECU
 
 
 
DIAGNOSIS
STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.
Use scan tool to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - Diagnosis/CAN Bus Diagnostics Table ).
 
STEP 2. Using scan tool MB991958, check the data list
Check the following data list .
  • Item No. B11: Odometer:rec.V1
  • Item No. B12: Power relay voltage:rec V1
  • Item No. B13: Vehicle speed:rec.V1
  • Item No. B21: Odometer:rec.V2
  • Item No. B22: Power relay voltage:rec V2
  • Item No. B23: Vehicle speed:rec.V2
  • Item No. B31: Odometer:rec.V3
  • Item No. B32: Power relay voltage:rec V3
  • Item No. B33: Vehicle speed:rec.V3
  • Item No. B41: Odometer:rec.V4
  • Item No. B42: Power relay voltage:rec V4
  • Item No. B43: Vehicle speed:rec.V4
  • Item No. B51: Odometer:rec.V5
  • Item No. B52: Power relay voltage:rec V5
  • Item No. B53: Vehicle speed:rec.V5
Is the check result normal?
Go to Step 3.
Check the combination meter and repair if necessary (Refer to GROUP 54A-combination meter ). Then go to Step 5.
 
STEP 3. Check the battery voltage.
Start the engine and measure the battery voltage (Refer to GROUP 54A - On-vehicle Service/Battery Test ).
Is the check result normal?
Go to Step 4.
Check the battery and repair if necessary (Refer to GROUP 54A - On-vehicle Service/Charging System , Battery ).
 
STEP 4. Check the charging system.
Start the engine and measure the charging system (Refer to GROUP 16 - On-vehicle Service/Generator Output Line Voltage Drop Test ).
Is the check result normal?
Go to Step 5.
Check the charging system and repair if necessary (Refer to GROUP 16 - Generator Assembly ).
 
STEP 5. Retest the system
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
Replace the electric power steering-ECU (Refer to ).