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 - Troubleshooting ).
Whenever ECU is replaced, ensure that the CAN bus lines are normal.
When the hydraulic unit assembly (integrated with ASTC-ECU) is replaced, always carry out the calibration of the steering wheel sensor and the G sensor (Refer to ).
OPERATION
The ASTC-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 ASTC-ECU.
The motor relay, which is incorporated in the ASTC-ECU, is always off unless the motor solenoid valve check is activated when the vehicle is started.
The ASTC-ECU activates the pump motor by turning on the ECU built-in motor relay when the ABS/ASTC 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 ASTC-ECU)
Past trouble
Carry out diagnosis with particular emphasis on connector(s) or wiring harness between the power supply circuit (+BM terminal) to the ASTC-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 ).
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnosis
Use the M.U.T.-III to diagnose the CAN bus lines.
Q.
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. Diagnosis code recheck after resetting CAN bus lines
Q.
Is diagnosis code No. C1266, C1271, C1273 or C1274 set?
Go to Step 3.
This diagnosis is complete.
STEP 3. Check the battery.
Refer to GROUP 54A - Battery Test .
Q.
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 ASTC-ECU connector.
(1)Connector check: ASTC-ECU connector
(2)Disconnect the connector and measure at the wiring harness side.
(3)Measure the resistance between +BM terminal and body earth. OK: No continuity
Q.
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 ASTC-ECU connector.
(1)Disconnect the connector and measure at the wiring harness side.
(2)Measure the voltage between +BM terminal and body earth. OK: Battery voltage
Q.
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 ASTC-ECU connector.
(1)Disconnect the connector and measure at the wiring harness side.
(2)Measure the resistance between terminals GND1 or GND2 and body earth. OK: Continuity exists (2 Ω or less).
Q.
Is the check result normal?
Go to Step 7.
An open circuit may be present in the earth circuit. Repair the wiring harness wires between ASTC-ECU connector terminal GND1 or GND2 and body earth. Then go to Step 7.
STEP 7. Diagnosis code recheck
Check again if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition switch: "LOCK" (OFF) position to "ON"
(3)Drive the vehicle until the vehicles speed reaches 20 km/h.
Q.
Is diagnosis code No. C1266, C1271, C1273 or C1274 set?
Replace the hydraulic unit assembly (integrated with ASTC-ECU) (Refer to ).
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).