Code No.C1540 Power supply voltage too high


caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C, CAN Bus Diagnostics Table).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION

    Power is supplied to the EPS-ECU from the battery or the ignition switch.

FUNCTION

    To control the steering column shaft assembly, the battery voltage is supplied to the EPS-ECU.

TROUBLE JUDGEMENT
Check Conditions
  • Power supply voltage is more than 17 V.
  • The power supply voltage is more than a predetermined voltage stored in the microcomputer, and the microcomputer determines that there is a problem in the power supply system.
Judgement Criterion
    The power supply monitor voltage does not meet a predetermined voltage stored in the microcomputer, and the microcomputer determines that there is a problem in the power supply system.
Fail Safe, Back Up Function
    The EPS-ECU stops the motor control and illuminates the electric power steering warning display, then sets the diagnosis code No. C1540.

PROBABLE CAUSES

  • Malfunction of CAN bus line
  • Defective battery
  • Charging system failed
  • Malfunction of the EPS-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 3
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ). On completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines
(1)Erase the diagnosis code.
(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code C1540 set?
Go to Step 3
This diagnosis is complete.

STEP 3. Check the battery voltage.
Start the engine and measure the battery voltage (Refer to GROUP 54A - Battery ).

Q. Is the check result normal?
Go to Step 4
Check the battery and repair if necessary (Refer to GROUP 54A - Battery ).Then go to Step 7.

STEP 4. Check the charging system.
Start the engine and measure the charging system (Refer to GROUP 16 - On-vehicle Service/Alternator Output Line Voltage Drop Test ).

Q. Is the check result normal?
Go to Step 5
Check the charging system and repair if necessary (Refer to GROUP 16 - Alternator Assembly <4B1, 4J1> or <4N1>).Then go to Step 7.

STEP 5. M.U.T.-III data list
Check the following data list .

  • Item No. 22: Power relay voltage

  • Item No. 23: Ignition voltage

Q. Is the check result normal?
Go to Step 7
Go to Step 6

STEP 6. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code C1540 set?
Replace the EPS-ECU (Refer to ).Then go to Step 7.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions ).

STEP 7. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code C1540 set?
Return to Step 1.
This diagnosis is complete.