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 ).
Whenever ECU is replaced, ensure that the CAN bus lines are normal.
When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor (Refer to , and ).

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.16 and 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 - CAN Bus Diagnosis table ). 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.

	Replace the battery.

STEP 5. Charging system check

Refer to GROUP 16 - Charging System

(2000),

(2200),

(2400) or

(3000).

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)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 pump motor 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 No.16 and body earth, and between terminal No.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 connector terminal No.16 and the body earth, and between the A-03 ASC-ECU connector terminal No.47 and the body earth.

	NO : Repair the defective connector.

STEP 10. Check whether the diagnosis code is reset.

(1)Erase the diagnosis code.

(2)Drive the vehicle at 20 km/h or more.

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. C1073 set?

	Replace the ASC-ECU (Refer to ). Then go to Step 11.

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

STEP 11. Check whether the diagnosis code is reset.

(1)Erase the diagnosis code.

(2)Drive the vehicle at 20 km/h or more.

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. C1073 set?

	Return to Step 1.

	This diagnosis is complete.