Code No.C1273: Pump motor driver circuit malfunction

OPERATION

The ABS/Active stability control system-ECU contains the power supply circuit (terminal No.45) for the motor pump. The motor pump is energised by the pump relay, which is incorporated in the ABS/Active stability control system-ECU.
The pump relay, which is incorporated in the ABS/Active stability control system-ECU, is always energising the motor pump unless the initial check is in progress when the ignition switch is turned on, or the recurrent system check is in progress.

DIAGNOSIS CODE SET CONDITIONS

The ABS/Active stability control system-ECU monitors the voltage which is produced by the rotation of the pump motor after turning on the motor relay. If this voltage is not created, the system determines that the motor relay is stuck off, and sets the diagnosis code.

PROBABLE CAUSES

Damaged wiring harness or connector
Malfunction of the hydraulic unit (integrated with ABS/Active stability control system-ECU)

DIAGNOSIS PROCEDURE

STEP 1. Connector check: A-06 ABS/Active stability control system-ECU connector

Q. Is the check result normal?

Go to Step 2.

Repair the defective connector.

STEP 2. Voltage measurement at the A-06 ABS/Active stability control system-ECU connector.

(1)Disconnect the A-06 ABS/Active stability control system-ECU connector, and connect special tool ABS Check Harness (MB991984) to the wiring harness-side connector.

note

Connect special tool ABS Check Harness (MB991984) to the ABS/Active stability control system-ECU.

(2)Measure the voltage while the Actuator Test is activating one of the valves (The voltage is created for three seconds after the Actuator Test is carried out).

(3)Voltage between special tool ABS Check Harness (MB991984) connector terminal No.45 and body earth
OK: more than 10 V

Q. Is the check result normal?

Go to Step 3.

Repair the wiring harness.

STEP 3. Resistance measurement at the A-06 ABS/Active stability control system-ECU connector.

(1)Disconnect the A-06 ABS/Active stability control system-ECU connector, and connect special tool ABS Check Harness (MB991984) to the wiring harness-side connector.

note

Do not connect special tool ABS Check Harness (MB991984) to the ABS/Active stability control system-ECU.

(2)Resistance between special tool ABS Check Harness (MB991984) connector terminal No.46 and body earth
OK: 5 Ω or less

Q. Is the check result normal?

Go to Step 4.

Repair the wiring harness.

STEP 4. Check whether the diagnosis code is reset.

caution

Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.

Check again if the diagnosis code is set.
(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)When driving at a constant speed of 15 km/h.
(6)Check if the diagnosis code is set.
(7)Turn the ignition switch to the "LOCK" (OFF) position.
(8)Disconnect M.U.T.-III.

Q. Is code No.C1273 set?

Replace the hydraulic unit (integrated with ABS/Active stability control system-ECU). Then perform the variant coding and write the VIN data (Refer to GROUP 00, Precautions Before Service - How to Perform Variant Coding

The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction