Code No. C1542: Fail-safe relay is stuck to OFF







caution
  • If the EPS-ECU sets the diagnosis code No. C1542, diagnose the CAN bus lines. If there is any fault in the CAN bus lines, an incorrect diagnosis code may be set.
  • Before replacing ECU, ensure that the communication circuit is normal.

DIAGNOSIS CODE SET CONDITIONS




  • Although the fail-safe relay (power relay) is turned on, the system is not energised and the microcomputer determines that the relay contact is open.
  • The fail-safe relay (power relay) is not turned on and the microcomputer determines that the relay contact is open.

CRITERIA FOR JUDGING MALFUNCTION



PROBABLE CAUSES



  • Defective wiring harness or connector in the power supply circuit to EPS-ECU
  • Malfunction of the EPS-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code
Recheck if the diagnosis code is set.
(1)Turn the electric motor switch to the "LOCK" (OFF) → "ON" position.
(2)Start the electric motor unit.
(3)Check if the diagnosis code No. C1542 and C1531 are set as the current trouble.

Q. Are the diagnosis code No. C1542 set?
Go to Step 2.
Go to Step 4.

STEP 2. Measure the resistance at B-114-1 EPS-ECU connector.
(1)Disconnect the connector and measure at the wiring harness side.
(2)Measure the resistance between B-114-1 EPS-ECU connector terminal No. 2 and the body earth.
OK: Continuity exists. (300 Ω or more)
(3)Measure the resistance between B-114-1 EPS-ECU connector terminal No. 1 and the body earth.
OK: Continuity exists. (300 Ω or more)

Q. Is the check result normal?
Go to Step 3.
Replace the steering gear & linkage assembly.

STEP 3. Diagnosis code recheck
Recheck if the diagnosis code is set.
(1)Turn the electric motor switch to the "LOCK" (OFF) → "ON" position.
(2)Check if the diagnosis code No. C1542 and C1531 are set as the current trouble.

Q. Are the diagnosis code No. C1542 set?
Replace EPS-ECU.
Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)

STEP 4. Measure the resistance at B-114-1 EPS-ECU connector.
(1)Disconnect the connector and measure at the wiring harness side.
(2)Measure the resistance between B-114-1 EPS-ECU connector terminal No. 1 and terminal No. 2.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?
Go to Step 5.
Repair the wiring harness and connector, or replace the steering gear box & linkage assembly.

STEP 5. Diagnosis code recheck
Recheck if the diagnosis code is set.
(1)Turn the electric motor switch to the "LOCK" (OFF) → "ON" position.
(2)Start the electric motor unit.
(3)Check if the diagnosis code No. C1542 is set as a current trouble.

Q. Is diagnosis code C1542 set?
Replace EPS-ECU.
Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)