Inspection Procedure 2: M.U.T.-III cannot communicate with electric power steering system <ECU power supply circuit system check>.

COMMENTS ON TROUBLE SYMPTOM
If the M.U.T.-III cannot communicate with the electric power steering system, the CAN bus lines may be defective. If the electric power steering system does not operate (power assist is not available), the electric power steering-ECU or its power supply may be defective.

PROBABLE CAUSES

  • Defective harness wire(s) or connector(s)
  • Malfunction of the electric power steering-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check the connectors and terminals.


  • Electric power steering-ECU connectors B-106 and B-105
Check the connectors above for improper engagement, terminal damage or terminal drawn in the connector case.

Q. Are the connectors and terminals in good condition?

Go to Step 2.

Repair the connector(s) or terminal(s).

STEP 2. Measure the voltage at electric power steering-ECU connector B-106.



  • Disconnect the connector, and measure at the wiring harness side.
  • IGNITION SWITCH: ON
  • Voltage between electric power steering-ECU connector B-106 terminal No.5 and body earth
OK: system voltage

Q. Is the check result normal?

Go to Step 3.

Go to Step 5.

STEP 3. Measure the voltage at electric power steering-ECU connector B-105.



  • Disconnect the connector, and measure at the wiring harness side.
  • Voltage between electric power steering-ECU connector B-105 terminal No.22 and body earth
OK: system voltage

Q. Is the check result normal?

Go to Step 4.

Go to Step 6.

STEP 4. Measure the resistance at electric power steering-ECU connector B-105.



  • Disconnect the connector, and measure at the wiring harness side.
  • Continuity between electric power steering-ECU connector B-105 terminal No.21 and body earth
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Go to Step 8.

Go to Step 7.

STEP 5. Check the wiring harness wires.


note Prior to the wiring harness inspection, check junction block connectors B-210 and B-229, and repair if necessary.



  • The harness wire between electric power steering-ECU connector B106 and ignition switch (IG1) B-240
Check the harness wire above for damage or other problem.

Q. Is the wiring harness in good condition?

Go to Step 8.

Repair the wiring harness.

STEP 6. Check the wiring harness wires.



  • Harness wire between electric power steering-ECU connector B-105 and fusible link No.4
Check the harness wire above for damage or other problem.

Q. Is the wiring harness in good condition?

Go to Step 8.

Repair the wiring harness.

STEP 7. Check the wiring harness wires.



  • Harness wire between electric power steering-ECU connector B-105 and body earth
Check the harness wire above for damage or other problem.

Q. Is the wiring harness in good condition?

Go to Step 8.

Repair the wiring harness.

STEP 8. Retest the system.

Q. Is the check result normal?
The malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .
Replace the electric power steering-ECU (Refer to ).