Code No.C1541 Power supply voltage too low


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 for energisation.

TROUBLE JUDGEMENT
Check Conditions
    The ETACS power supply circuit system diagnosis code is not set.
Judgement Criterion
  • Power supply voltage is less than 8V.
  • 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 tapers the motor control and illuminates the electric power steering warning display, then sets the diagnosis code No. C1541.

PROBABLE CAUSES

  • Malfunction of CAN bus line
  • Defective battery
  • Charging system failed
  • Defective harness wire(s) or connector(s)

    • Short or open circuit between the EPS-ECU, the ETACS-ECU and the fusible link or loose connector contact
    • Open circuit between the body earth and the EPS-ECU or loose connector contact
  • Malfunction of the ETACS-ECU
  • 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 C1541 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 10.

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> or <6B3>).Then go to Step 10.

STEP 5. Voltage measurement at the EPS-ECU connector (IG1, +BB, GND terminal)
(1) Measure the EPS-ECU voltage without disconnecting the connector (by backprobing).
(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3)Measure the voltage between the EPS-ECU connector (IG1 terminal) and the EPS-ECU connector (GND terminal) or body earth.
OK: Approximately system voltage
(4)Measure the voltage between the EPS-ECU connector (+BB terminal) and the EPS-ECU connector (GND terminal) or body earth.
OK: Approximately system voltage

Q. Is the check result normal?
Go to Step 8
Go to Step 6

STEP 6. Check of short to power supply, short to earth, and open circuit in +BB line between fusible link and EPS-ECU connector

Q. Is the check result normal?
Go to Step 7
Repair the fusible link, connector(s) or wiring harness.

STEP 7. Check of short to power supply, short to earth, and open circuit in IG1 line between EPS-ECU connector and ETACS-ECU connector

Q. Is the check result normal?
Go to Step 8
Repair the connector(s) or wiring harness.

STEP 8. 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 10
Go to Step 9

STEP 9. 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 C1541 set?
Replace the EPS-ECU (Refer to ).Then go to Step 10.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions ).

STEP 10. 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 C1541 set?
Return to Step 1.
This diagnosis is complete.