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DTC C1540 Power supply voltage too high
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect DTC 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 12V Starter Battery or the electric motor switch.
 
 
 
FUNCTION
  • To control the steering column shaft assembly, the 12V Starter Battery voltage is supplied to the EPS-ECU.
 
 
 
TROUBLE JUDGMENT
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.
Judgment 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 DTC No. C1540.
 
 
 
TROUBLESHOOTING HINTS
  • Malfunction of CAN bus line
  • Defective 12V Starter Battery
  • Malfunction of the EPS-ECU
 
 
 
 
DIAGNOSIS
STEP 1. Scan tool (M.U.T.-IIISE) CAN bus diagnostics.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ."
(2) Turn on the power supply mode of the electric motor switch.
(3) Diagnose the CAN bus line.
(4) Turn off the power supply mode of the electric motor switch.
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. DTC recheck after resetting CAN bus lines.
(1) Erase the DTC.
(2) Turn off the power supply mode of the electric motor switch.
(3) Turn on the power supply mode of the electric motor switch.
(4) Check if the DTC is set.
Is DTC C1540 set?
Go to Step 3.
This diagnosis is complete.
 
STEP 3. Check the 12V Starter Battery voltage.
Start the electric motor unit and measure the 12V Starter Battery voltage (Refer to GROUP 54A - 12V Starter Battery ).
Is the check result normal?
Go to Step 4.
Replace the 12V Starter Battery.
 
STEP 4. Scan tool (M.U.T.-IIISE) data list.
Check the following data list (Refer to ).
  • Item No. 22: Power relay voltage
  • Item No. 23: Ignition voltage
Is the check result normal?
Go to Step 5.
Replace the EPS-ECU (Refer to ).
 
STEP 5. Check whether the DTC is set again.
(1) Erase the DTC.
(2) Turn off the power supply mode of the electric motor switch.
(3) Turn on the power supply mode of the electric motor switch.
(4) Check if the DTC is set.
Is DTC C1540 set?
Replace the EPS-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions ).