Code No.C1861: Power supply low voltage
caution |
- If there is any problem in the CAN bus lines, an incorrect diagnosis code 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.
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OPERATION
Power is supplied to the EPS-ECU from the battery or the ignition switch.
DIAGNOSIS CODE SET CONDITION
The power supply voltage is less than a predetermined voltage stored in the microcomputer, and the microcomputer determines that there is a problem in the power supply system.
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 EPS-ECU, the ETACS-ECU and the fusible link or loose connector contact
- Open circuit between the body earth and the EPS-ECU or loose connector contact
- Malfunction of the EPS-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics
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Use M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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Go to Step 3.
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Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ). On completion, go to Step 2.
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STEP 2. Diagnosis code recheck after resetting CAN bus lines
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Check if the diagnosis code is set.
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Q.
Is diagnosis code C1861 set?
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Go to Step 3.
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This diagnosis is complete.
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STEP 3. Check the battery voltage.
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Start the engine and measure the battery voltage (Refer to GROUP 54A - Battery Test ).
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Q.
Is the check result normal?
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Go to Step 4.
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Check the battery and repair if necessary (Refer to GROUP 54A - Battery Test , GROUP 54A - Battery Removal and Installation ). Then go to Step 10.
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STEP 4. Check the charging system.
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Start the engine and measure the charging system (Refer to GROUP 16 - On-vehicle Service/Alternator Output Line Voltage Drop Test )
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Q.
Is the check result normal?
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Go to Step 5.
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Check the charging system and repair if necessary (Refer to GROUP 16 - Alternator Assembly ). Then go to Step 10.
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STEP 5. Wiring harness check
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(1)Check the wiring harness between the EPS-ECU connector terminal +BB and the fusible link for damage or other problem.
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(2)Check the wiring harness between the junction block connector terminal and the fusible link for damage or other problem.
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(3)Check the wiring harness between the EPS-ECU connector terminal GND and the body earth point for damage or other problem.
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Q.
Is the check result normal?
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Go to Step 6.
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Repair the defective connector(s) or terminal(s), or repair the defective wiring harness. Then go to Step 10.
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STEP 6. Voltage measurement at the junction block connector
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(1)Measure the junction block voltage without disconnecting the connector (by backprobing).
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(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Measure the voltage between the junction block connector terminals. OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 7.
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Check the fusible link or the junction block and repair if necessary. Then go to Step 10.
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STEP 7. Voltage measurement at the EPS-ECU connector
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(1) Measure the EPS-ECU voltage without disconnecting the connector (by backprobing).
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(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Measure the voltage between the EPS-ECU connector terminal IG1 and the EPS-ECU connector terminal GND. OK: Battery voltage
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(4)Measure the voltage between the EPS-ECU connector terminals +BB and GND. OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 8.
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Check the fusible link or the junction block and repair if necessary. Then go to Step 10.
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STEP 8. M.U.T.-III data list
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Check the following data list (Refer to ).
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- Item No. 22: Power relay voltage
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- Item No. 23: Ignition voltage
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Q.
Is the check result normal?
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Go to Step 10.
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Go to Step 9.
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STEP 9. Check whether the diagnosis code is set again.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Check if the diagnosis code is set.
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Q.
Is diagnosis code C1861 set?
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Replace the EPS-ECU (Refer to ). Then go to Step 10.
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions ).
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STEP 10. Check whether the diagnosis code is set again.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Check if the diagnosis code is set.
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Q.
Is diagnosis code C1861 set?
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Return to Step 1.
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This diagnosis is complete.
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