Code No. C1266:
Motor stuck
Code No. C1271: Motor drive circuit
Code No. C1273: Motor drive
circuit stuck off
Code No. C1274: Motor drive circuit stuck on
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 -
CAN Bus Diagnostics Table
).
- 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 (+BM terminal) for
the pump motor. The pump motor is energised by the motor relay, which is incorporated in the
ASC-ECU.
- The motor relay, which is incorporated in the ASC-ECU, is always off unless the
motor solenoid valve check is activated when the vehicle is started.
- The ASC-ECU activates the pump motor by turning on the ECU built-in motor relay when
the ABS/ASC is working.
DIAGNOSIS CODE SET CONDITIONS
These diagnosis codes will be set under the cases below.
Code No. C1266 Motor stuck
- The ECU monitors the voltage, which is created by the pump motor coasting, after
the motor relay is turned off. If the voltage continues only for too short period, the ECU determines
that the pump motor is not running smoothly (i.e. motor seizure), and sets this diagnosis code.
Code No. C1271 Motor drive circuit
- The ECU monitors the power supply voltage to the motor. If the voltage is lower than
a predetermined value, the ECU sets this diagnosis code as a failure in the motor power supply
circuit.
Code No. C1273 Motor drive circuit stuck off
- If the voltage, which is created by the pump motor, is abnormal after the motor
relay is turned on, the ECU determines that the motor relay is stuck off, and sets this diagnosis code.
Code No. C1274 Motor drive circuit stuck on
- If the voltage, which is created by the pump motor, is abnormal after the motor
relay is turned off, the ECU determines that the motor relay is 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 connector(s) or
wiring harness between the power supply circuit (+BM terminal) to the ASC-ECU motor
or earth circuit (GND1 and GND2 terminals). 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. C1266, C1271, C1273 or C1274 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 (Refer to GROUP 54A -
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: 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 +BM 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 ACS-ECU connector +BM 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 +BM 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 ACS-ECU connector +BM 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 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. C1266, C1271, C1273 or C1274 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. C1266, C1271, C1273 or C1274 set?
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Return to Step 3.
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This diagnosis is complete.
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