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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 diagnostic trouble code may be stored. 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 steering wheel sensor and the G and yaw rate sensor (Refer to and ).
 
 
OPERATION
  • The ASC-ECU contains the power supply circuit (+BM terminal) for the pump motor. The pump motor is energized 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.
 
 
DIAGNOSTIC TROUBLE CODE SET CONDITIONS
These diagnostic trouble codes will be stored 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 stores this diagnostic trouble 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 stores this diagnostic trouble 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 stores this diagnostic trouble 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 stores this diagnostic trouble code.
 
 
PROBABLE CAUSES
Current trouble
  • Battery failure
  • Damaged harness wires and connectors
  • Malfunction of 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 ground circuit (GND1 and GND2 terminals). For diagnosis procedures, refer to How to treat past trouble (GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).
 
 
DIAGNOSIS
STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.
Use the scan tool MB991958 to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 3.
Repair the CAN bus line. (Refer to GROUP 54C - CAN Bus Trouble Symptom Chart .) On completion, go to Step 2.
 
STEP 2. Diagnostic trouble code recheck after resetting CAN bus lines
Is diagnostic trouble code No. C1266, C1271, C1273 or C1274 stored?
Go to Step 3.
This diagnosis is complete.
 
STEP 3. Check the battery.
Refer to GROUP 54A - Battery Test .
Is the battery in good condition?
Go to Step 4.
Charge or replace the battery. Then go to Step 7.
 
STEP 4. Measure the resistance at the ASC-ECU connector.
(1) Connector check: ASC-ECU connector
(2) Disconnect the connector and measure at the wiring harness side.
(3) Measure the resistance between +BM terminal and body ground.
OK: No continuity
Is the check result normal?
Go to Step 5.
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 7.
 
STEP 5. Measure the voltage at the ASC-ECU connector.
(1) Disconnect the connector and measure at the wiring harness side.
(2) Measure the voltage between +BM terminal and body ground.
OK: Battery voltage
Is the check result normal?
Go to Step 6.
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 7 .
 
STEP 6. Measure the resistance at the ASC-ECU connector.
(1) Disconnect the connector and measure at the wiring harness side.
(2) Measure the resistance between terminals GND1 or GND2 and body ground.
OK: Continuity exists (2 Ω or less).
Is the check result normal?
Go to Step 7.
An open circuit may be present in the ground circuit. Repair the wiring harness wires between ASC-ECU connector terminal GND1 or GND2 and body ground. Then go to Step 7.
 
STEP 7. Diagnostic trouble code recheck
Check again if the diagnostic trouble code is stored.
(1) Erase the diagnostic trouble code.
(2) Ignition switch: LOCK (OFF) position to ON
(3) Drive the vehicle until the vehicles speed reaches 20 km/h.
Is diagnostic trouble code No. C1266, C1271, C1273 or C1274 stored?
Replace the hydraulic unit (integrated with ASC-ECU). (Refer to .)
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).