Code No.31 Defective Levelling Unit


caution Whenever the ECU is replaced, ensure that the communication circuit is normal.














TROUBLE JUDGMENT
If the headlamp levelling unit signal line is short-circuited, diagnosis code No. 31 is set.

COMMENTS ON TROUBLE SYMPTOM
The headlamp assembly (headlamp levelling unit), the headlamp automatic levelling-ECU, or wiring harness and connectors between the two may be defective.

PROBABLE CAUSES

  • Malfunction of the headlamp levelling unit
  • Malfunction of the headlamp automatic levelling-ECU
  • Damaged wiring harness and connectors

DIAGNOSIS PROCEDURE

STEP 1. Connector check: A-21 Headlamp levelling unit (LH) connector, D-125 headlamp automatic levelling-ECU connector

Q. Is the check result normal?
Go to Step 2.
Repair the defective connector.

STEP 2. Check the wiring harness between A-21 headlamp levelling unit (LH) connector (terminal No. 1) and D-125 headlamp automatic levelling-ECU connector (terminal No. 3).

  • Check the signal lines for open circuit and short circuit.
note Prior to the wiring harness inspection, check intermediate connector D-239, and repair if necessary.

Q. Is the check result normal?
Go to Step 3.
Repair the wiring harness.

STEP 3. Check whether the diagnosis code is reset.

Q. Is diagnosis code No. 31 set?
Go to Step 4.
A poor connection, open circuit, or other intermittent malfunctions between the headlamp levelling unit (LH) and the headlamp automatic levelling-ECU. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .)

STEP 4. Connector check: A-42 Headlamp levelling unit (RH) connector

Q. Is the check result normal?
Go to Step 5.
Repair the defective connector.

STEP 5. Check the wiring harness between A-42 headlamp levelling unit (RH) connector (terminal No. 1) and D-125 headlamp automatic levelling-ECU connector (terminal No. 12).

  • Check the signal lines for open circuit and short circuit.
note Prior to the wiring harness inspection, check intermediate connector D-239, and repair if necessary.

Q. Is the check result normal?
Go to Step 6.
Repair the wiring harness.

STEP 6. Check whether the diagnosis code is reset.

Q. Is diagnosis code No. 31 set?
Go to Step 7.
A poor connection, open circuit, or other intermittent malfunctions between the headlamp levelling unit and the headlamp automatic levelling-ECU. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .)

STEP 7. Check whether the diagnosis code is reset.
Replace the headlamp assembly (LH), and then check again if diagnosis code No.31 is set.

Q. Is diagnosis code No. 31 set?
Go to Step 8.
The diagnosis is complete.

STEP 8. Check whether the diagnosis code is reset.
Replace the headlamp assembly (RH), and then check again if diagnosis code No.31 is set.

Q. Is diagnosis code No. 31 set?
Replace the headlamp automatic levelling-ECU.
The diagnosis is complete.