Code No.C1278: Solenoid valve relay (open circuit)
Code No.C1279: Solenoid valve relay (short circuit)





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



DIAGNOSIS CODE SET CONDITIONS



Code No. C1278
  • When the solenoid valve relay monitor judges that the solenoid valve relay is turned "ON" although it actually is turned "OFF"
Code No. C1279
  • When the solenoid valve relay monitor judges that the solenoid valve relay is turned "OFF" although it actually is turned "ON"

PROBABLE CAUSES




  • Fusible link malfunction
  • Damaged wiring harness or connector
  • Malfunction of the hydraulic unit assembly (integrated with ASTC-ECU)

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)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.

Q. Are the diagnosis codes No.C1278 or C1279 set?
Go to Step 3.
The procedure is complete.

STEP 3. Connector check: A-48 ASTC-ECU connector

Q. Is the check result normal?
Go to Step 4.
Repair or replace the damaged component(s). Then go to Step 9.

STEP 4. Fusible link check: Check the fusible link No.21

Q. Is the check result normal?
Go to Step 6.
Go to Step 5.

STEP 5. Resistance measurement at A-48 ASTC-ECU connector
(1)Remove the fusible link No.21.
(2)Disconnect the A-48 ASTC-ECU connector.
(3)Measure the resistance between the A-48 ASTC-ECU connector terminal No.1 and body earth.
OK: No continuity

Q. Is the check result normal?
Replace the fusible link No.21. Then go to Step 9.
Repair the wiring harness between the fusible link No.21 and the A-48 ASTC-ECU connector terminal No.1. Then replace the fusible link No.21. Then go to Step 9.

STEP 6. Voltage measurement at A-48 ASTC-ECU connector
(1)Disconnect the A-48 ASTC-ECU connector.
(2)Measure the voltage between the A-48 ASTC-ECU connector terminal No.1 and the body earth.
OK: Battery voltage

Q. Is the check result normal?
Go to Step 7.
The open circuit may be present in the solenoid valve power supply circuit. Repair the wiring harness between the fusible link No.21 and the A-48 ASTC-ECU connector terminal No.1. Then go to Step 9.

STEP 7. Resistance measurement at A-48 ASTC-ECU connector
(1)Disconnect the A-48 ASTC-ECU connector.
(2)Measure the resistance between the A-48 ASTC-ECU connector terminal No.12 and the body earth, and between the terminal No.24 and body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?
Go to Step 8.
The open circuit may be present in the earth circuit. Repair the wiring harness between the A-48 ASTC-ECU connector terminal No.12 and the body earth, and between the A-48 ASTC-ECU connector terminal No.24 and the body earth. Then go to Step 9.

STEP 8. Check whether the diagnosis code is reset.
(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 that the ABS warning lamp, Brake warning lamp, ASTC indicator lamp and ASTC OFF indicator lamp goes out.
(6)Check if the diagnosis code is set.
(7)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Are the diagnosis code No.C1278 or C1279 set?
Replace the hydraulic unit assembly (integrated with ASTC-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 reset.
(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 that the ABS warning lamp, Brake warning lamp, ASTC indicator lamp and ASTC OFF indicator lamp goes out.
(6)Check if the diagnosis code is set.
(7)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Are the diagnosis code No.C1278 or C1279 set?
Go to Step 1.
This diagnosis is complete.