Inspection Procedure 1: Scan Tool (M.U.T.-IIISE) Cannot Communicate With Electric Power Steering System <Ecu Power Supply Circuit System Check>: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB992006: Extra Fine Probe

1. STEP 1. Using scan tool (M.U.T.-IIISE), diagnose CAN bus line. 
   CAUTION: To 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).
   1. Connect scan tool (M.U.T.-IIISE). Refer to "HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) ."
   2. Use scan tool (M.U.T.-IIISE) to diagnose the CAN bus lines.

   Q: Is the check result normal? 

   YES  : Go to Step 2.

   NO  : Repair the CAN bus lines (Refer to CAN BUS DIAGNOSTICS TABLE ).

2. STEP 2. DTC recheck after resetting CAN bus lines 
   1. Erase the DTC.
   2. Engine start
   3. Check if the DTC is set.

   Q: Is DTC C1541 set? 

   YES  : Go to Step 3.

   NO  : This diagnosis is complete.

3. STEP 3. Voltage measurement at the EPS-ECU connector (+BB, GND terminal) 
   1. Measure the EPS-ECU voltage without disconnecting the connector (by backprobing).
   2. Engine start
   3. Measure the voltage between the EPS-ECU connector (+B terminal) and the EPS-ECU connector (GND terminal) or body ground.

   OK: Approximately system voltage 

   Q: Is the check result normal? 

   YES  : Go to Step  6.

   NO  : Go to Step 4.

4. STEP 4. Check the fusible link. 

   Q: Is the check result normal? 

   YES  : Go to Step 5.

   NO  : Repair the fusible link.

5. STEP 5. Check of short to power supply, short to ground, and open circuit in +B line between fusible link and EPS-ECU connector 
   NOTE: Prior to the wiring harness inspection, check intermediate connector and repair if necessary.

   Q: Is the check result normal? 

   YES  : Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS ).

   NO  : Repair the fusible link, connector(s) or wiring harness.

6. STEP 6. Voltage measurement at the EPS-ECU connector (IG1, GND terminal) 
   1. Measure the EPS-ECU voltage without disconnecting the connector (by backprobing).
   2. Engine start
   3. Measure the voltage between the EPS-ECU connector (IG1 terminal) and the EPS-ECU connector (GND terminal) or body ground.

      OK: Approximately system voltage 

   Q: Is the check result normal? 

   YES  : Go to Step  8.

   NO  : Go to Step 7.

7. STEP 7. Check of short to power supply, short to ground, and open circuit in IG1 line between EPS-ECU connector and ETACS-ECU connector 
   NOTE: Prior to the wiring harness inspection, check joint connector and repair if necessary.

   Q: Is the check result normal? 

   YES  : Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS ).

   NO  : Repair the connector(s) or wiring harness.

8. STEP 8. Resistance measurement at the EPS-ECU connector (GND terminal). 
   1. Disconnect the connector, and measure at the wiring harness side.
   2. Resistance between the EPS-ECU connector (GND terminal) and body ground

      OK: Continuity exists (2 ohms or less) 

   Q: Is the check result normal? 

   YES  : Go to Step  10.

   NO  : Go to Step 9.

9. STEP 9. Check of open circuit in GND line between EPS-ECU connector and body ground. 
   NOTE: Prior to the wiring harness inspection, check intermediate connector and repair if necessary.

   Q: Is the check result normal? 

   YES  : Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS ).

   NO  : Repair the connector(s) or wiring harness.

10. STEP 10. Retest the system 

    Q: Is the check result normal? 

    YES  : Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS ).

    NO  : Replace the EPS-ECU (Refer to TIE ROD END BALL JOINT DUST COVER REPLACEMENT ).