Code No. C1276:
Valve power supply circuit
Code No. C1278: Valve power circuit stuck off
Code
No. C1279: Valve power circuit stuck on
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- 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
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- 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 G and yaw rate sensor and the steering wheel sensor (Refer to and ).
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OPERATION
- The ASC-ECU contains the power supply circuit (+BV terminal) for
the solenoid valve. The solenoid valve is energised by the valve relay, which is incorporated
in the ASC-ECU.
- The valve relay, which is incorporated in the ASC-ECU, is always ON except for during
the initial check at ignition switch is turned "ON" as well as for during the system check that
is periodically repeated. While the system is active, the power is supplied to the solenoid
valve at all times.
DIAGNOSIS CODE SET CONDITIONS
These diagnosis codes will be set under the cases below.
Code No. C1276 Valve power supply circuit
- The 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 power supply circuit.
Code No. C1278 Valve power circuit stuck off
- When the solenoid valve is not energised even after the solenoid valve relay is turned
ON, the ECU determines that the solenoid valve relay stuck OFF and sets this diagnosis code.
Code No. C1279 Valve power circuit stuck on
- When the solenoid valve is energised even after the solenoid valve relay is turned
OFF, the ECU determines that the solenoid valve relay stuck ON and sets this diagnosis code.
PROBABLE CAUSES
Current trouble
- Battery failure
- Damaged harness wires and connectors
- Malfunction of the hydraulic unit assembly (integrated with ASC-ECU)
Past trouble
- Carry out diagnosis with particular emphasis on wiring harness and
connector failures in the power supply circuit (+
BV terminal) to ASC-ECU solenoid
valve or earth circuit (terminals GND1 and GND2). For diagnosis procedures, refer to How to
treat past trouble (GROUP 00 -
How to Use Troubleshooting/Inspection Service Points).
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STEP 1. M.U.T.-III CAN bus diagnosis.
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Use the M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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 Go to Step 3.
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 Repair the CAN bus line (Refer to GROUP 54C -
Troubleshooting ).
On completion, go to Step 2.
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STEP 2. Diagnosis code recheck after resetting CAN bus lines.
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Q.
Is diagnosis code No. C1276, C1278 or C1279 set?
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Go to Step 3.
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This diagnosis is complete.
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STEP 3. Check the battery.
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Refer to GROUP 54A -
Battery Test.
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Q.
Is the battery in good condition?
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Go to Step 4.
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Charge or replace the battery. Then go to Step 8.
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STEP 4. Measure the resistance at the ASC-ECU connector.
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(1)Connector check: hydraulic unit assembly (integrated with ASC-ECU) connector.
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(2)Disconnect the connector and measure at the wiring harness side.
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(3)Measure the resistance between +BV terminal and body earth.
OK: No continuity
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Q.
Is the check result normal?
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Go to Step 5.
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The power supply circuit may be short. Repair the wiring harness wires or connectors
between the hydraulic unit assembly (integrated with ASC-ECU) connector +BV terminal and
the fusible links, or replace the fusible links. Then go to Step 8.
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STEP 5. Measure the voltage at the ASC-ECU connector.
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(1)Disconnect the connector and measure at the wiring harness side.
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(2)Measure the voltage between +BV terminal and body earth.
OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 6.
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The power supply circuit may be open. Repair the wiring harness wires or connectors
between the hydraulic unit assembly (integrated with ASC-ECU) connector +BV terminal and
the fusible links. Then go to Step 8.
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STEP 6. Measure the resistance at the ASC-ECU connector.
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(1)Disconnect the connector and measure at the wiring harness side.
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(2)Measure the resistance between terminals GND1 or GND2 and body earth.
OK: Continuity exists (2 Ω
or less).
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Q.
Is the check result normal?
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Go to Step 7.
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An open circuit may be present in the earth circuit. Repair the wiring harness
wires between hydraulic unit assembly (integrated with ASC-ECU) connector terminal GND1 or GND2
and body earth. Then go to Step 8.
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STEP 7. Check whether the diagnosis code is set again.
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(1)Turn the ignition switch to the "ON" position.
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(2)Turn the ignition switch to the "LOCK" (OFF) position.
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(3)Drive the vehicle at 20 km/h or more.
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Q.
Is diagnosis code No. C1276, C1278 or C1279 set?
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Replace the hydraulic unit assembly (integrated with ASC-ECU) (Refer to ).
Then go to Step 8.
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The trouble can be an intermittent malfunction (Refer to GROUP 00 -
How
to Cope with Intermittent Malfunction).
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STEP 8. Check whether the diagnosis code is set again.
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(1)Turn the ignition switch to the "ON" position.
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(2)Turn the ignition switch to the "LOCK" (OFF) position.
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(3)Drive the vehicle at 20 km/h or more.
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Q.
Is diagnosis code No. C1276, C1278 or C1279 set?
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Return to Step 3.
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This diagnosis is complete.
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