Diagnostic system check-electric power steering controls

  • If there are no complaints on drivability, do not perform these diagnostic steps unless otherwise instructed in other sections.
  • Check for related Service Bulletins before starting the diagnosis.
  • Do not clear the DTC unless instructed to do so in a diagnostic step.
  • The battery should be fully charged.
  • The battery cable should be normal and securely connected.
  • The ground of the EPS motor control unit should be securely connected to the correct position.
  • The EPS motor control unit harness connector should be clean and correctly connected.
  • The EPS motor control unit terminals should be clean and correctly connected.

1. Scan tool power-up check

1) Connect the scan tool.

2) Power up the scan tool. Does the scan tool power up?

Yes

=>Go to Central gateway control unit communication verification.

No

Go to Scan tool does not power up.

Refer to "51.Engine Control 1A.Troubleshooting(4JJ3 with DPD) Scan tool does not power up".

Refer to "51.Engine Control 1A.Troubleshooting(4JJ3 without DPD) Scan tool does not power up".

2. Central gateway control unit communication verification

1) Turn ON the ignition switch.

2) Verify communication with the central gateway control unit using the scan tool. Can communication with the central gateway control unit be established?

Yes

=>Go to EPS motor control unit communication verification.

No

Go to Lost communication with the central gateway control unit.

Refer to "64.Body Control 10I.Troubleshooting(Central GateWay) lost communication with the central gateway control unit".

3. EPS motor control unit communication verification

1) Verify that communication can be established with the EPS motor control unit using the scan tool. Can communication with the EPS motor control unit be established?

Yes

=>Go to Current DTC check.

No

Go to Lost communication with the EPS motor control unit.

Refer to "56.Steering Control 6A.Troubleshooting lost communication with the EPS motor control unit".

4. Current DTC check

1) Observe the DTC information with a scan tool. Is a DTC set?

Yes

Go to the applicable DTC diagnosis.

No

=>Go to Steering system failure warning light illumination check.

5. Steering system failure warning light illumination check

1) Start the engine.

2) Check the steering system failure warning light. Does the steering system failure warning light illuminate for approximately 3 seconds and then turn OFF?

Yes

=>Go to Customer's concern check.

No

Go to Steering system failure warning light illuminating circuit system check.

Refer to "56.Steering Control 6A.Troubleshooting steering system failure warning light illuminating circuit system check".

6. Customer's concern check

1) Check if the customer's concern is related to the systems other than the electric power steering. Is the customer's concern related to the systems other than the electric power steering?

Yes

Go to the applicable control system inspection.

No

=>Go to Symptom check.

7. Symptom check

1) Operate the vehicle and check the following symptoms. Is there any applicable symptom?

  • Unstable steering
  • Vibration of the steering wheel
  • Steering wheel is difficult to control
  • Abnormal kickback of the steering wheel
  • Abnormal noises of power steering
  • Excessive play of the steering
  • Large force required to operate the steering
  • Improper return of the steering wheel to the center position

Yes

Go to the applicable symptom diagnosis.

Refer to "207.Steering 20D.Symptom unstable steering".

Refer to "207.Steering 20D.Symptom vibration of the steering wheel".

Refer to "207.Steering 20D.Symptom steering wheel is difficult to control".

Refer to "207.Steering 20D.Symptom abnormal kickback of the steering wheel".

Refer to "207.Steering 20D.Symptom abnormal noises of power steering".

Refer to "207.Steering 20D.Symptom excessive play of the steering".

Refer to "207.Steering 20D.Symptom large force required to operate the steering".

Refer to "207.Steering 20D.Symptom improper return of the steering wheel to the center position".

No

Go to Intermittent conditions of electric power steering control system.

Refer to "207.Steering 20D.Symptom intermittent conditions of electric power steering control system".

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