COde No.C1861 Power supply voltage abnormality (low voltage)


caution
  • If the electric power steering-ECU sets diagnosis code No.C1861, diagnose the CAN bus lines. If there is any fault in the CAN bus lines, an incorrect diagnosis code may be set.
  • Whenever the ECU is replaced, ensure that the communication circuit is normal.


DIAGNOSIS CODE SET CONDITIONS

  • 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.
    • Criteria for judging malfunction
    • Power supply voltage is less than 9 V

PROBABLE CAUSES

  • Defective battery
  • Charging system failed
  • Malfunction of the electric power steering-ECU
  • Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. Check the battery voltage.
Start the engine and measure the battery voltage.

Q. Does the voltage measure 10 V or more?
Go to Step 2.
Check the battery and the charging system and repair if necessary (Refer to GROUP 54A - Battery - Battery Test or GROUP 16 - On-vehicle Service - Regulated Voltage Test ).

STEP 2. Check the voltage in the power supply line.
Disconnect connector B-105 and measure the voltage.

  • Between connector B-105 terminal 22 and body earth
OK: System voltage

Q. Is the measurement value normal?
Go to Step 3.
Check the wiring harness wires and connectors between fusible link No.4 and electric power steering-ECU connector B-105 and repair if necessary.

STEP 3. Check the resistance in the earth line.
Disconnect connector B-105 and measure the resistance.

  • Between connector B-105 terminal 21 and body earth
OK: Continuity exists (2 Ω or less)

Q. Is the measurement value normal?
Go to Step 4.
Check the wiring harness wires and connectors between body earth and electric power steering-ECU connector B-105 and repair if necessary.

STEP 4. Check whether the diagnosis code is reset.

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Check if the diagnosis code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.
(7)Disconnect M.U.T.-III.

Q. Is diagnosis code C1861 set?

Replace the electric power steering-ECU (Refer to ).

The malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .