Code No.C1276: Valve system

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 54F, CAN bus-line diagnostic flow

OPERATION

The ABS-ECU contains the power supply circuit (terminal 1) for the solenoid valve. The solenoid valve is energised by the valve relay, which is incorporated in the ABS-ECU.
The valve relay, which is incorporated in the ABS-ECU, is always energising the solenoid valve 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

These diagnosis codes will be set under the cases below.

The ABS-ECU monitors the power supply voltage to the solenoid valve. If the voltage is lower than the predetermined value, the ECU sets this diagnosis code as a failure in the valve relay circuit.

PROBABLE CAUSES

The most likely causes for these diagnosis codes to set are:

Damaged wiring harness or connector
Malfunction of the hydraulic unit (integrated with ABS-ECU)

DIAGNOSIS

STEP 1. M.U.T.-III CAN bus diagnostics

caution

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

(1)Connect M.U.T.-III to the 16-pin diagnosis connector.
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the check result normal?

Go to Step 3.

Repair the CAN bus line (Refer to GROUP 54F, CAN bus line Diagnostic flow

). Then go to Step 2.

STEP 2. 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.

(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. Is code No.C1276 set?

Go to Step 3.

The procedure is complete.

STEP 3. Voltage measurement at ABS-ECU connector A-03.

(1)Disconnect the connector A-03, and connect special tool ABS Check Harness (MB991974) to the wiring harness-side connector.

note

Do not connect special tool ABS Check Harness (MB991974) to the ABS-ECU.

(2)Turn the ignition switch to the "ON" position.
(3)Measure the voltage between terminal 1 and earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 5.

Go to Step 4.

STEP 4. Check ABS-ECU connector A-03 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is the check result normal?

An open or short circuit may be present in the solenoid valve power supply circuit. Repair the wiring harness between ABS-ECU connector A-03 terminal 1 and fusible link No.3. Then go to Step 8.

Repair or replace the damaged component(s). Then go to Step 8.

STEP 5. Measure the resistance at ABS-ECU connector A-03.

(1)Disconnect the connector A-03, and connect special tool ABS Check Harness (MB991974) to the wiring harness-side connector.

note

Do not connect special tool ABS Check Harness (MB991974) to the ABS-ECU.

(2)Measure the resistance between terminal 26 and earth.
OK: 2 ohm or less

Q. Is the result normal?

Go to Step 7.

Go to Step 6.

STEP 6. Check ABS-ECU connector A-03 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is the result normal?

An open circuit may be present in the earth circuit. Repair the wiring harness between ABS-ECU connector A-03 terminal 26 and the body earth. Then go to Step 8.

Repair or replace the damaged component(s). Then go to Step 8.

STEP 7. Check whether the diagnosis code is reset.

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)Check if the diagnosis code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is code No.C1276 set?

Replace the hydraulic unit (integrated with ABS-ECU). Then go to Step 8.

It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction

STEP 8. Check whether the diagnosis code is reset.

Q. Is code No.C1276 set?

Go to Step 1.

The procedure is complete.