U0251

DTC U0251: AWC time-out error (Local CAN)

DTC U0440: AWC communication error (Local CAN)

DTC U0435: AWC signal abnormality (Local CAN)





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.
^ Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
^ When the hydraulic unit (integrated with ASC-ECU) is replaced, always perform the calibration of steering wheel sensor, G and yaw rate sensor, brake fluid pressure sensor, cut valve, and inlet valve.

CIRCUIT OPERATION
S-AWC-ECU outputs the signal to ASC-ECU via the special CAN bus lines (Local CAN).

DTC SET CONDITIONS
These diagnostic trouble codes will be set under the cases below.

DTC UO251
^ Signals sent from S-AWC-ECU to ASC-ECU cannot be received for a specified period.

DTC U0440
^ Signals sent from S-AWC-ECU to ASC-ECU have an error.

DTC U0435
^ brake control request of outside the specified range is output by S-AWC-ECU.

PROBABLE CAUSES
^ Wiring harness or connector failure in special CAN bus lines (Local CAN) between ASC-ECU and S-AWC-ECU
^ S-AWC-ECU malfunction
^ ASC-ECU malfunction

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

STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.
Using scan tool MB991958, diagnose the CAN bus lines.

Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. After repairing the CAN bus line, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line

Q: Are DTC UO251, U0440, and U0435 set?
YES: Go to Step 3.
NO: This diagnosis is complete.

STEP 3. Diagnostic trouble code check of other systems using scan tool
Using scan tool MB991958, check if a diagnostic trouble code is set in S-AWC-ECU.

Q: Is other DTC set?
YES: Troubleshoot the relevant diagnostic trouble code, and then go to Step 8.
NO: Go to Step 4.

STEP 4. Connector check: A-05 ASC-ECU connector, C-46 S-AWC-ECU connector, C-47 intermediate connector, C-50 joint connector

Q: Is the check result normal?
YES: Go to Step 5.
NO: Repair the connector, and then go to Step 8.

STEP 5. Wiring harness check between A-05 ASC-ECU connector terminal No. 18 and C-46 S-AWC-ECU connector terminal No. 9, between A-05 ASC-ECU connector terminal No. 19 and C-46 S-AWC-ECU connector terminal No. 10
^ Open or short circuit check of communication circuit

Q: Is the check result normal?
YES: Go to Step 6.
NO: Repair the wiring harness, and then go to Step 8.

STEP 6. Check whether the DTC is reset.

Q: Are DTC UO251, U0440, and U0435 set?
YES: Replace the S-AWC-ECU. Then go to Step 7.
NO: Intermittent malfunction.

STEP 7. Check whether the DTC is reset.

Q: Are DTC UO251, U0440, and U0435 set?
YES: Replace the hydraulic unit (incorporates in ASC-ECU). Then go to Step 8.
NO: The procedure is complete.

STEP 8. Check whether the DTC is reset.

Q: Are DTC UO251, U0440, and U0435 set?
YES: Return to Step 1.
NO: The procedure is complete.