Code No. C1073 Faulty motor drive circuit








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, Trouble code diagnosis ).

OPERATION

  • ASC-ECU contains the power supply circuit (terminal No. 1) for the pump motor. The pump motor is energised by the motor switch, which is incorporated in ASC-ECU.
  • The pump motor switch, 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 pump motor switch.

DIAGNOSIS CODE SET CONDITIONS
If the pump motor switch voltage drop indicates high value when the pump motor operates or after the operation, the pump motor operation is stopped and this diagnosis code is set.

PROBABLE CAUSES
Current trouble
  • Fusible link malfunction
  • Damaged wiring harness and connectors
  • Abnormality in battery or alternator
  • ASC-ECU malfunction
Past trouble
  • Carry out diagnosis with particular emphasis on wiring harness and connector failures between the power supply circuit (A-03 ASC-ECU connector terminal No. 1) to the ASC-ECU motor and the earth circuit (A-03 ASC-ECU connector terminal No. 47). For diagnosis procedures, refer to How to treat past trouble (GROUP 00 - How to Cope with Intermittent 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 - Troubleshooting ). On completion, go to Step 2.

STEP 2. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. C1073 set?
Go to Step 3.
This diagnosis is complete.

STEP 3. Fusible link check: Check the fusible link No. 26.

Q. Is the check result normal?
Go to Step 4.
Replace the fusible link No. 26.

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.

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).

STEP 6. Voltage measurement at the A-03 ASC-ECU connector

(1)Disconnect the ASC-ECU connector, connect special tool ASC check harness (MB991997) to the harness-side connector, and then measure the voltage at the special tool connector side.
note Do not connect the special tool ASC check harness (MB991997) to ASC-ECU.
(2)Turn the ignition switch to the ON position.
(3)Measure the voltage between the terminal No. 1 and the body earth.
OK: Approximately battery voltage

Q. Is the check result normal?

Go to Step 8.

Go to Step 7.

STEP 7. Connector check: A-03 ASC-ECU connector

Q. Is the check result normal?
The open or short circuit may be present in the solenoid valve power supply circuit. Repair the wiring harness between the A-03 ASC-ECU connector terminal No. 1 and the fusible link No. 26.
NO : Repair the defective connector.

STEP 8. Resistance measurement at A-03 ASC-ECU connector

(1)Disconnect the ASC-ECU connector, connect special tool ASC check harness (MB991997) to the harness-side connector, and then measure the resistance at the special tool connector side.
note Do not connect the special tool ASC check harness (MB991997) to ASC-ECU.
(2)Resistance between terminal 47 and body earth
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Go to Step 10.

Go to Step 9.

STEP 9. Connector check: A-03 ASC-ECU connector

Q. Is the check result normal?
An open circuit may be present in the earth circuit. Repair the wiring harness between the A-03 ASC-ECU terminal No. 47 and the body earth.
NO : Repair the defective connector.

STEP 10. Check whether the diagnosis code is reset.

  • Drive the vehicle at 20 km/h or more.

Q. Is the diagnosis code No. C1073 set?
Replace the ASC-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).