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DTC U0251: AWC time-out error (Local CAN)
DTC U0440: AWC communication error in AWC (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.(Refer to , , , and .)

CIRCUIT OPERATION
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 U0251
  • Signals sent from AWC-ECU to ASC-ECU cannot be received for a specified period.
DTC U0440
  • Signals sent from AWC-ECU to ASC-ECU have an error.
DTC U0435
  • A brake control request of outside the specified range is output by AWC-ECU.

PROBABLE CAUSES

  • Wiring harness or connector failure in special CAN bus lines (Local CAN) between ASC-ECU and AWC-ECU
  • 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 A

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?
Go to Step 3.
Repair the CAN bus lines. (Refer to GROUP 54C - Troubleshooting .) After repairing the CAN bus line, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line

Q. Is DTC U0251, U0440 or U0435 set?
Go to Step 3.
This diagnosis is complete.

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

Q. Is other DTC set?
Troubleshoot the relevant diagnostic trouble code, and then go to Step 8.
Go to Step 4.

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

Q. Is the check result normal?
Go to Step 5.
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 AWC-ECU connector terminal No. 9, between A-05 ASC-ECU connector terminal No. 19 and C-46 AWC-ECU connector terminal No. 10

  • Open or short circuit check of communication circuit

Q. Is the check result normal?
Go to Step 6.
Repair the wiring harness, and then go to Step 8.

STEP 6. Check whether the DTC is reset.

Q. Are DTC U0251, U0440, and U0435 set?
Replace the AWC-ECU. (Refer to GROUP 22A - Manual Transaxle, AWC-ECU .) Then go to Step 7.
Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)

STEP 7. Check whether the DTC is reset.

Q. Is DTC U0251, U0440 or U0435 set?
Replace the hydraulic unit (incorporates in ASC-ECU). (Refer to .) Then go to Step 8.
The procedure is complete.

STEP 8. Check whether the DTC is reset.

Q. Is DTC U0251, U0440 or U0435 set?
Return to Step 1.
The procedure is complete.