C1541: Fail-safe relay is stuck to ON







caution
  • If the EPS-ECU sets the diagnosis code No. C1541, 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 supply relay) is turned off, the system is energised, but the microcomputer determines that the relay contact is closed.
  • The fail-safe relay (power supply relay) is not turned off, and the microcomputer determines that the relay contact is closed.

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. C1541 is set as a current trouble.

Q. Is diagnosis code C1541 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. Is diagnosis code C1541 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. C1541 is set as a current trouble.

Q. Is diagnosis code C1541 set?
Replace EPS-ECU.
Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)