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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 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 for energization.
 
 
 
TROUBLE JUDGMENT
Check Conditions
  • The ETACS power supply circuit system DTC is not set.
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 EPS-ECU tapers the motor control and illuminates the electric power steering warning display, then sets DTC No. C1541.
 
 
 
TROUBLESHOOTING HINTS
  • Malfunction of CAN bus line
  • Defective 12V Starter Battery
  • 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 ground and the EPS-ECU or loose connector contact
  • Malfunction of the ETACS-ECU
  • Malfunction of the EPS-ECU
 
 
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
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 C1541 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 8.
Go to Step 5.
 
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 on the power supply mode of the electric motor switch.
(3) Measure the voltage between the EPS-ECU connector (IG1 terminal) and the EPS-ECU connector (GND terminal) or body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
(4) Turn off the power supply mode of the electric motor switch.
(5) Measure the voltage between the EPS-ECU connector (+BB terminal) and the EPS-ECU connector (GND terminal) or body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Is the check result normal?
Go to Step 8.
Go to Step 6.
 
STEP 6. Check of short to power supply, short to ground, and open circuit in +BB line between fusible link and EPS-ECU connector.
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 ground, and open circuit in IG1 line between EPS-ECU connector and ETACS-ECU connector.
Is the check result normal?
Go to Step 8.
Repair the connector(s) or wiring harness.
 
STEP 8. 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 C1541 set?
Replace the EPS-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions ).