SRS Air Bag Diagnosis
DTC U1073: Bus OffCAUTION:
- If DTC U1073 is set in the SRS-ECU, diagnose the CAN main bus line.
- Whenever the ECU is replaced, ensure that the communication circuit is normal.
DTC SET CONDITION
DTC U1073 will be stored when the SRS-ECU ceases CAN communication (bus off) and then resumes the communication when the ignition switch is turned to the "LOCK" (OFF) position. However, if the vehicle condition return to normal, DTC number U1073 will be automatically erased, and the SRS warning light will switch off.
TECHNICAL DESCRIPTION (COMMENT)
The wiring harness wire or connectors may have loose, corroded, or damage terminals, or terminals pushed back in the connector, or the SRS-ECU may be defective.
TROUBLESHOOTING HINTS
- Defective connector(s) or wiring harness
- Malfunction of the SRS-ECU
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: 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 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 2.
NO : Repair the CAN bus lines (Refer to Controlled Area Network (CAN), precautions on how to repair the can bus lines).
STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
1. Connect scan tool MB991958 to the data link connector
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the check result satisfactory?
YES : There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to general (body and Chassis), How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).
NO : Replace the A/C-ECU. On completion, check that the DTC is not reset.