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Inspection Procedure 1: Scan tool (M.U.T.-IIISE) cannot communicate with electric power steering system <ECU power supply circuit system check>.
 
 
 
 
COMMENTS ON TROUBLE SYMPTOM
If the scan tool (M.U.T.-IIISE) cannot communicate with the electric power steering system, the CAN bus lines may be defective. If the electric power steering system does not operate, the EPS-ECU or its power supply may be defective.
 
 
 
TROUBLESHOOTING HINTS
  • Malfunction of CAN bus line
  • Defective harness wire(s) or connector(s)
    • Short or open circuit between the EPS-ECU and the ETACS-ECU, the fusible link or loose connector contact
    • Open circuit between the body ground and the EPS-ECU or loose connector contact
  • Malfunction of the ETACS-ECU
  • Malfunction of the EPS-ECU
 
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Scan tool (M.U.T.-IIISE) CAN bus diagnostics.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch 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 on the power supply mode of the electric motor switch.
(3) Diagnose the CAN bus line.
(4) Turn off the power supply mode of the electric motor switch.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
 
STEP 2. Voltage measurement at the EPS-ECU connector (IG1, +BB, GND terminal).
(1) Measure the EPS-ECU voltage without disconnecting the connector (by backprobing).
(2) Turn on the power supply mode of the electric motor switch.
(3) Measure the voltage between the EPS-ECU connector (IG1 terminal) and the EPS-ECU connector (GND terminal) or body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
(4) Turn off the power supply mode of the electric motor switch.
(5) Measure the voltage between the EPS-ECU connector (+BB terminal) and the EPS-ECU connector (GND terminal) or body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Is the check result normal?
Go to Step 5.
Go to Step 3.
 
STEP 3. Check of short to power supply, short to ground, and open circuit in +BB line between fusible link and EPS-ECU connector.
Is the check result normal?
Go to Step 4.
Repair the fusible link, connector(s) or wiring harness.
 
STEP 4. Check of short to power supply, short to ground, and open circuit in IG1 line between EPS-ECU connector and ETACS-ECU connector.
Is the check result normal?
Go to Step 5.
Repair the connector(s) or wiring harness.
 
STEP 5. Retest the system.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Replace the EPS-ECU (Refer to ).