Code No. C1266 Abnormality in pump motor (stuck)
Code No. C1273 Abnormality in pump motor relay (stuck off)
Code No. C1274 Abnormality in pump motor relay (stuck on)







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 ASC-ECU contains the power supply circuit (terminal No.1) for the motor pump. The motor pump is energised by the pump relay, which is incorporated in the ASC-ECU.
  • The motor relay, which is incorporated in ASC-ECU, is always off unless the motor solenoid valve check is activated when the vehicle is started.
  • ASC-ECU activates the pump motor by turning on the ECU built-in motor relay when the ABS is working.

DIAGNOSIS CODE SET CONDITIONS
These diagnosis codes will be set under the cases below:
Code No.C1266
  • The ECU monitors the voltage, which is created by the pump motor coasting, after the motor relay is turned off. If the voltage continues only for too short period, the ECU determines that the pump motor is not running smoothly (i.e. motor seizure), and sets this diagnosis code.
Code No.C1273
  • If the voltage, which is created by the pump motor, is abnormal after the motor relay is turned on, the ECU determines that the motor relay is stuck off, and sets this diagnosis code.
Code No.C1274
  • If the voltage, which is created by the pump motor, is abnormal after the motor relay is turned off, the ECU determines that the motor relay is stuck on, and sets this diagnosis code.

PROBABLE CAUSES
Current trouble
  • Damaged wiring harness and connectors
  • ASC-ECU malfunction
Past trouble
  • Carry out diagnosis with particular emphasis on connector(s) or wiring harness in the power supply circuit (terminal No.1) to the ASC-ECU motor and earth circuit (terminal No.13 and No.38).For diagnosis procedures, refer to How to treat past trouble (GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
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. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No.C1266, C1273 or C1274 set?
Go to Step 3.
This diagnosis is complete.

STEP 3. Auxiliary battery check
Refer to GROUP 54A - Battery Test .

Q. Is the battery in good condition?
Go to Step 4.
Charge or replace the auxiliary battery. Then go to Step 10.

STEP 4. Connector check: A-14 ASC-ECU connector

Q. Is the check result normal?
Go to Step 5.
NO : Repair the defective connector. Then go to Step 10.

STEP 5. Fusible link check: Check the fusible link No.22.
Visually check for open circuit in the fusible link No.22.

Q. Is the check result normal?
Go to Step 7.
Go to Step 6.

STEP 6. Resistance measurement at A-14 ASC-ECU connector
(1)Disconnect the ASC-ECU connector, connect special tool ABS check harness (MB992335) to the harness-side connector, and then measure the resistance at the special tool connector side.
note Do not connect the special tool ABS check harness (MB992335) to ASC-ECU.

(2)Measure the resistance between the terminal No.1 and the body earth.
OK: No continuity

Q. Is the check result normal?

Replace the fusible link No.22. Then go to Step 10.

The short circuit may be present in the power supply circuit. Repair the wiring harness between the A-14 ASC-ECU connector terminal No.1 and the fusible link No.22, and then replace the fusible link No.22. Then go to Step 10.

STEP 7. Voltage measurement at the A-14 ASC-ECU connector
(1)Disconnect the ASC-ECU connector, connect special tool ABS check harness (MB992335) to the harness-side connector, and then measure the voltage at the special tool connector side.
note Do not connect the special tool ABS check harness (MB992335) to ASC-ECU.

(2)Measure the voltage between the terminal No.1 and the body earth.
OK: Approximately system voltage

Q. Is the check result normal?

Go to Step 8.

The open circuit may be present in the power supply circuit. Repair the wiring harness between the A-14 ASC-ECU connector terminal No.1 and the fusible link No.22. Then go to Step 10.

STEP 8. Resistance measurement at A-14 ASC-ECU connector
(1)Disconnect the ASC-ECU connector, connect special tool ABS check harness (MB992335) to the harness-side connector, and then measure the resistance at the special tool connector side.
note Do not connect the special tool ABS check harness (MB992335) to ASC-ECU.

(2)Measure the resistance between the terminal No.13 and the body earth, and between the terminal No.38 and the body earth
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Go to Step 9.

An open circuit may be present in the earth circuit. Repair the wiring harness between the A-14 ASC-ECU connector terminal No.13 and the body earth, and between the A-14 ASC-ECU connector terminal No.38 and the body earth. Then go to Step 10.

STEP 9. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h or higher.

Q. Is the diagnosis code No.C1266, C1273 or C1274 set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ). Then go to Step 10.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).

STEP 10. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h or higher.

Q. Is the diagnosis code No.C1266, C1273 or C1274 set?
Return to Step 1.
This diagnosis is complete.