C1271
DTC C1271: Motor drive circuitSolenoid Valve and Motor Power Supply Circuit
CAUTION: If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines.
CAUTION: Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
CAUTION: When I replace hydraulic unit (integrated with TCL/ASC-ECU), Always perform the calibration of steering wheel sensor and yaw rate sensor.
CIRCUIT OPERATION
^ The TCL/ASC-ECU contains the power supply circuit (terminal 1) for the pump motor. The pump motor is energized by the motor relay, which is incorporated in the TCL/ASC-ECU.
^ The motor relay, which is incorporated in the TCL/ASC-ECU, is always off unless the motor solenoid valve check is activated when the vehicle is started.
^ The TCL/ASC-ECU activates the pump motor by turning on the ECU built-in motor relay when the ABS is working.
TCL/ASC DTC SET CONDITIONS
^ When pump motor drive time or a voltage descent of a pump motor switch after drive showed a high value, stop pump motor drive, and this DTC is output.
TROUBLESHOOTING HINTS (The most likely causes for these DTCs are to set are:)
Current trouble
^ Defective battery
^ Charging system failed
^ Damaged wiring harness or connector
^ Malfunction of the hydraulic unit (integrated with TCL/ASC-ECU)
Past trouble
^ Carry out diagnosis with particular emphasis on connector(s) or wiring harness in the power supply circuit (terminal 1) to the TCL/ASC-ECU motor or ground circuit (terminal 16, 47). For diagnosis procedures, refer to "How to cope with past trouble".
DIAGNOSIS
Required Special Tools:
^ MB991958: Scan Tool (M.U.T-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A
^ MB991997: ASC Check Harness
STEP 1. Using scan tool MB991958, diagnose the CAN bus line.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link 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 CAN bus line found to be normal?
YES: Go to Step 3.
NO: Repair the CAN bus line. Then go to Step 2.
STEP 2. Recheck for diagnostic trouble code.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Turn the ignition switch to the "ON" position.
(2) Erase the DTC.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
(4) Turn the ignition switch to the "ON" position.
(5) Check if the DTC is set.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC C1271 set?
YES: Go to Step 3.
NO: The procedure is complete.
STEP 3. Measure the voltage at TCL/ASC-ECU connector A-38.
(1) Disconnect the connector A-38, and connect special tool MB991997 to the wiring harness-side connector.
NOTE: Do not connect special tool MB991997 to the TCL/ASC-ECU.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 1 and ground. It should be approximately 12 volts (battery positive voltage).
Q: Is the voltage approximately 12 volts (battery positive voltage)?
YES: Go to Step 5.
NO: Go to Step 4.
STEP 4. Check TCL/ASC-ECU connector A-38 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is TCL/ASC-ECU connector A-38 damaged?
YES: Repair or replace the damaged component(s). Refer to Harness Connector Inspection. Then go to Step 8.
NO: An open or short circuit may be present in the solenoid valve power supply circuit. Repair the wiring harness between TCL/ASC-ECU connector A-38 terminal 1 and fusible link No. 3. Then go to Step 8.
STEP 5. Measure the resistance at TCL/ASC-ECU connector A38.
(1) Disconnect the connector A-38, and connect special tool MB991997 to the wiring harness-side connector.
NOTE: Do not connect special tool MB991997 to the TCL/ASC-ECU.
(2) Measure the resistance between terminal 16, 47 and ground. It should be 2 ohms or less.
Q: Is the measured resistance 2 ohms or less?
YES: Go to Step 7.
NO: Go to Step 6.
STEP 6. Check TCL/ASC-ECU connector A-38 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is TCL/ASC-ECU connector A-38 damaged?
YES: Repair or replace the damaged component(s). Refer to Harness Connector Inspection. Then go to Step 8.
NO: An open circuit may be present in the ground circuit. Repair the wiring harness between TCL/ASC-ECU connector A-38 terminal 16, 47 and the body ground. Then go to Step 8.
STEP 7. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Turn the ignition switch to the "ON" position.
(2) Erase the DTC
(3) Turn the ignition switch to the "LOCK" (OFF) position.
(4) Turn the ignition switch to the "ON" position.
(5) Check if the DTC is set.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC C1271 set?
YES: Replace the hydraulic unit (integrated with TCL/ASC-ECU). Then go to Step 8.
NO: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points -How to Cope with Intermittent Malfunction.
STEP 8. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Turn the ignition switch to the "ON" position.
(2) Erase the DTC.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
(4) Turn the ignition switch to the "ON" position.
(5) Check if the DTC is set.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC C1271 set?
YES: Go to Step 1.
NO: The procedure is complete.