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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 fusible link (+B).
  • Power is supplied to the motor from the EPS-ECU.
 
 
 
FUNCTION
The EPS-ECU monitors the voltage supplied from the ignition switch (IG1) and the power supply voltage supplied from the fusible link.
 
 
 
TROUBLE JUDGMENT
Check Conditions
  • Engine start
Judgment Criterion
  • EPS-ECU power supply voltage is more than threshold.
  • 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.
Fail Safe, Back Up Function
  • The EPS-ECU is in motor control output limit state, turns on the electric steering warning display, and sets DTC C1540.
 
 
 
TROUBLESHOOTING HINTS
  • Defective battery
  • Charging system failed
  • Malfunction of the EPS-ECU
 
 
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), check whether the other DTC is set.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position 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) Use scan tool (M.U.T.-IIISE) to check that other DTC is set in the ECU corresponding to the relevant diagnosis.
Is other DTC set?
Troubleshoot for the relevant DTC.
Go to Step 2.
 
STEP 2. Battery check
Refer to GROUP 54A - Battery Test .
Is the battery in good condition?
Go to Step 3.
Replace the battery (Refer to GROUP 54A - Battery ).
 
STEP 3. Charging system check
Refer to GROUP 16 - On-vehicle Service/Generator Output Line Voltage Drop Test .
Is the charging system in good condition?
Go to Step 4.
Repair or replace the charging system component(s) (Refer to GROUP 16 - Generator ).
 
STEP 4. Using scan tool (M.U.T.-IIISE), check the data list.
Check the following data list (Refer to ).
  • Item No. 33: System1 PIG voltage
  • Item No. 34: System2 PIG voltage
  • Item No. 35: IG voltage
Is the check result normal?
Go to Step 5.
Replace the EPS-ECU (Refer to ).
 
STEP 5. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
(1) Engine start
(2) Check if the DTC is set.
Is the DTC C1540 set?
Replace the EPS-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions ).