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 ).
Before replacing the ECU, ensure that the communication circuit is normal.

OPERATION

The ABS-ECU is energised by the ignition switch (IG1) through J/B fuse.
Power supply for ABS solenoid valve is supplied to the ABS-ECU via fusible link.
Power supply for ABS motor is supplied to the ABS-ECU via fusible link.
The wheel speed sensors are energised via ABS-ECU.

DIAGNOSIS CODE SET CONDITION

This code is set if the solenoid valve power supply circuit drops abnormally.

PROBABLE CAUSES

Damaged wiring harness or connector
Battery abnormality
Charging system failed
ABS-ECU malfunction
Battery terminal looseness
Fusible link malfunction

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis

Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

	Go to Step 3.

	Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ). Then go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines

(1)Erase the diagnosis code.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Turn the ignition switch to the "ON" position.

(4)Check if the diagnosis code is set.

Q. Is diagnosis code No.C1861 set?

	Go to Step 3.

	This diagnosis is complete.

STEP 3. Check the fusible link or the fuse.

Visually check for open circuit in the fusible link or the fuse.

Q. Is the check result normal?

	Go to Step 4.

	Replace the fusible link or fuse. Then go to Step 9.

STEP 4. Battery check

Refer to GROUP 54A - Battery Test

Q. Is the battery in good condition?

	Go to Step 5.

	Charge or replace the battery. Then go to Step 9.

STEP 5. Charging system check

Refer to GROUP 16 - Charging System

Q. Is the charging system in good condition?

	Go to Step 6.

	Repair or replace the charging system component(s). Then go to Step 9.

STEP 6. Resistance measurement at ABS-ECU connector

(1)Disconnect the junction block connector.

(2)Disconnect the fusible link.

(3)Disconnect the ABS-ECU connector, and measure at the wiring harness-side connector.

(4)Measure the resistance between the ABS-ECU connector +BV, +BM, IG1 terminal and the body earth.
OK: No continuity

Q. Is the check result normal?

	Go to Step 7.

	The short circuit may be present in the power supply circuit. Repair the damaged connector or the wiring harness between the ABS-ECU connector +BV, +BM, IG1 terminal and the fusible link, the junction block connector terminal. Then go to Step 9.

STEP 7. Voltage measurement at ABS-ECU connector

(1)Disconnect the ABS-ECU connector.

(2)Turn the ignition switch to the "ON" position.

(3)Measure the resistance between the ABS-ECU connector +BV, +BM, IG1 terminal and the body earth.
OK: Battery voltage

Q. Is the check result normal?

	Go to Step 8.

	The open circuit may be present in the power supply circuit. Repair the damaged connector or the wiring harness between the ABS-ECU connector +BV, +BM, IG1 terminal and the fusible link, the junction block connector terminal. Then go to Step 9.

STEP 8. Check whether the diagnosis code is set again.

(1)Erase the diagnosis code.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Turn the ignition switch to the "ON" position.

(4)Check if the diagnosis code is set.

Q. Is diagnosis code No. C1861 set?

	Replace the hydraulic unit [(integrated with ABS-ECU) Refer to ]. Then go to Step 9.

	Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions ).

STEP 9. Check whether the diagnosis code is set again.

(1)Erase the diagnosis code.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Turn the ignition switch to the "ON" position.

(4)Check if the diagnosis code is set.

Q. Is diagnosis code No. C1861 set?

	Return to Step 1.

	This diagnosis is complete.