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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 electric power steering-ECU from the battery or the ignition switch.
 
 
 
FUNCTION
  • To control the steering column shaft assembly, the battery voltage is supplied to the electric power steering-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 electric power steering-ECU stops the motor control and illuminates the electric power steering warning symbol, then sets DTC No. C1540.
 
 
 
PROBABLE CAUSES
  • Malfunction of CAN bus line
  • Defective battery
  • Charging system failed
  • Malfunction of the electric power steering-ECU
 
 
 
 
DIAGNOSIS
STEP 1. Scan tool (M.U.T.-III) CAN bus diagnostics
Use scan tool (M.U.T.-III) to diagnose the CAN bus lines.
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 the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3) Check if the DTC is set.
Is DTC 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 ).
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/Generator Output Line Voltage Drop Test ).
Is the check result normal?
Go to Step 5.
Check the charging system and repair if necessary Refer to GROUP 16 - Generator Assembly ).Then go to Step 7.
 
STEP 5. Scan tool (M.U.T.-III) data list
Check the following data list .
  • Item No. 22: Power relay voltage
  • Item No. 23: Ignition voltage
Is the check result normal?
Go to Step 7.
Go to Step 6.
 
STEP 6. Check whether the DTC is set again.
(1) Erase the DTC.
(2) Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3) Check if the DTC is set.
Is DTC C1540 set?
Replace the electric power steering-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 DTC is set again.
(1) Erase the DTC.
(2) Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3) Check if the DTC is set.
Is DTC C1540 set?
Return to Step 1.
This diagnosis is complete.