Code No.C1861: Low voltage at ASTC-ECU power supply









caution If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Diagnose the CAN bus lines before the diagnosis codes (Refer to GROUP 54C - CAN Bus Diagnostics Table .).

OPERATION



  • The ASTC-ECU is energized by the ignition switch (IG1) through multi-purpose fuse No.15 and the ASTC-ECU terminal 25.
  • Power supply for control solenoid valve and linear valve are supplied to the ASTC-ECU terminal 1 via fusible link 21.
  • Power supply for ABS motor is supplied to the ASTC-ECU terminal 13 via fusible link 22.
  • The wheel speed sensors are energised via ASTC-ECU terminal No. 25.

DIAGNOSIS CODE SET CONDITION



PROBABLE CAUSES




  • Battery abnormality
  • Charging system failed
  • Damaged wiring harness or connector
  • Malfunction of the hydraulic unit assembly (integrated with ASTC-ECU)
  • Battery terminal looseness

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 .). On completion, 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 the diagnosis code No.C1861 set?
Go to Step 3.
This diagnosis is complete.

STEP 3. Check the fusible link No.21, No.22 or the fuse No.15.
Visually check for open circuit in the fusible link No.21, No.22 or the fuse No.15.

Q. Is the check result normal?
Go to Step 4.
Replace the fusible link or fuse. Then go to Step 10.

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 10.

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 10.

STEP 6. Connector check: A-48 ASTC-ECU connector, C-207 junction block connector, C-210 junction block connector, C-307 ignition switch (IG1) connector

Q. Is the check result normal?
Go to Step 7.
NO : Repair the damaged connector. Then go to Step 10.

STEP 7. Resistance measurement at A-48 ASTC-ECU connector
(1)Disconnect the C-210 junction block connector.
(2)Disconnect the fusible link No.21 and No.22.
(3)Disconnect the A-48 ASTC-ECU connector, and measure at the wiring harness-side connector.
(4)Measure the resistance between the A-48 ASTC-ECU connector terminal No.1, No.13, No.25 and the body earth.
OK: No continuity

Q. Is the check result normal?
Go to Step 8.
The short circuit may be present in the power supply circuit. Repair the wiring harness between the A-48 ASTC-ECU connector terminal No.1, No.13, No.25 and the fusible link No.21, No.22, the C-210 junction block connector terminal No.8. Then go to Step 10.

STEP 8. Voltage measurement at A-48 ASTC-ECU connector
(1)Disconnect the A-48 ASTC-ECU connector.
(2)Turn the ignition switch to the "ON" position.
(3)Measure the resistance between the A-48 ASTC-ECU connector terminal No.1, No.13, No.25 and the body earth.
OK: Battery voltage

Q. Is the check result normal?
Go to Step 9.
The open circuit may be present in the power supply circuit. Repair the wiring harness between the A-48 ASTC-ECU connector terminal No.1, No.13, No.25 and the fusible link No.21, No.22, the C-210 junction block connector terminal No.8. Then go to Step 10.

STEP 9. Check whether the diagnosis code is reset.
(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 the diagnosis code No. C1861 set?
Replace the hydraulic unit (integrated with ASTC-ECU) (Refer to .). Then go to Step 10.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions .).

STEP 10. Check whether the diagnosis code is reset.
(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 the diagnosis code No. C1861 set?
Return to Step 1.
This diagnosis is complete.