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DTC C1541 Power supply voltage too low
 
 
 
 
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 for energization.
 
 
 
TROUBLE JUDGMENT
Check Conditions
  • During engine running.
Judgment 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 electric power steering-ECU tapers the motor control and illuminates the electric power steering warning symbol, then sets DTC 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 electric power steering-ECU, the ETACS-ECU and the fusible link or loose connector contact
    • Open circuit between the body ground and the electric power steering-ECU or loose connector contact
  • Malfunction of the ETACS-ECU
  • Malfunction of the electric power steering-ECU
 
 
 
 
DIAGNOSIS
STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.
Use scan tool to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54C - Diagnosis/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 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 - On-vehicle Service/Battery Test ).
Is the check result normal?
Go to Step 4.
Check the battery and repair if necessary (Refer to GROUP 54A - Battery Charging , Battery ). Then go to Step 11.
 
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 11.
 
STEP 5. Check the following connector.
Check the connectors below for improper engagement, terminal damage or terminal drawn in the connector case.
  • C-144 and C-145 electric power steering-ECU connector
  • C-408 and C-417 ETACS-ECU connector
  • C-127, C-146 and C-147 intermediate connector
  • C-04 joint connector
  • No.34 and No.35 fusible link
  • Body ground point
Is the connectors and terminals in good condition?
Go to Step 6.
Repair the defective connector(s) or terminal(s). Then go to Step 11.
 
STEP 6. Wiring harness check
(1) Check the wiring harness between the C-145 electric power steering-ECU connector terminal No.11 and the fusible link No.35 for damage or other problem.
(2) Check the wiring harness between the C-144 electric power steering-ECU connector terminal No.1, the C-146 intermediate connector terminal No.3, the C-127 intermediate connector terminal No.9, the C-04 joint connector terminal No.5, the C-04 joint connector terminal No.11 and the C-417 ETACS-ECU connector terminal No.5 for damage or other problem.
(3) Check the wiring harness between the C-408 ETACS-ECU connector terminal No.1 and the fusible link No.34 for damage or other problem.
(4) Check the wiring harness between the C-145 electric power steering-ECU connector terminal No.12 and the body ground point and the C-147 intermediate connector terminal No.2 for damage or other problem.
Is the wiring harness in good condition?
Go to Step 7.
Repair the defective wiring harness. Then go to Step 11.
 
STEP 7. Voltage measurement at the ETACS-ECU connector
(1) Measure the ETACS-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 C-408 ETACS-ECU connector terminal No.1 and the C-417 ETACS-ECU connector terminal No.5.
OK: Approximately system voltage
Is the check result normal?
Go to Step 8.
Check the fusible link or the ETACS-ECU and repair if necessary (Refer to GROUP 54A - ETACS ).Then go to Step 11.
 
STEP 8. Voltage measurement at the electric power steering-ECU connector
(1) Measure the electric power steering-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 C-144 electric power steering-ECU connector terminal No.1 and the C-145 electric power steering-ECU connector terminal No.12.
OK: Approximately system voltage
(4) Measure the voltage between the C-145 electric power steering-ECU connector terminals No.11 and No.12.
OK: Approximately system voltage
Is the check result normal?
Go to Step 9.
Check the fusible link or the ETACS-ECU and repair if necessary (Refer to GROUP 54A - ETACS ).Then go to Step 11.
 
STEP 9. Using scan tool MB991958, check the 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 11.
Go to Step 10.
 
STEP 10. 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 C1541 set?
Replace the electric power steering-ECU (Refer to ).Then go to Step 11.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
 
STEP 11. 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 C1541 set?
Return to Step 1.
This diagnosis is complete.