Code No. U1102: ASC timeout
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- If diagnosis code No. U1102 is set, diagnose the CAN bus lines.
- When replacing the ECU, always check that the SRS circuit is normal.
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FUNCTION
If signal from the ASTC-ECU cannot be received for 500 milliseconds or more, the SRS-ECU will set diagnosis code No. U1102.
TROUBLE JUDGEMENT
Because of the CAN-B bus circuit malfunction, if SRS-ECU becomes unable to perform the normal data transmission, SRS-ECU determines that an abnormality is present.
PROBABLE CAUSES
- Malfunction of CAN bus line
- Malfunction of hydraulic unit assembly (integrated with ASTC-ECU)
- Malfunction of SRS-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics
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Use the M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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 Go to Step 2.
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 Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting  ). On completion, go to Step 5.
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STEP 2. Check the M.U.T.-III Diagnosis code for other systems
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Check whether the ASTC-ECU sets a diagnosis code.
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Q.
Is the diagnosis code set?
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Diagnose the ASTC-ECU. Refer to GROUP 35C, Troubleshooting .
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Go to Step 3.
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STEP 3. Check whether the diagnosis code is set again.
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Check again if the diagnosis code is set in the SRS-ECU.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
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(3)On completion, check whether the diagnosis code is set again.
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Q.
Is the diagnosis code set?
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Replace the hydraulic unit assembly (integrated with ASTC-ECU). After replacing the ECU, carry out the CAN bus diagnostics. Then go to Step 4.
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A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the ASTC-ECU and the SRS-ECU (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
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STEP 4. Check whether the diagnosis code is set again.
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Check again if the diagnosis code is set in the SRS-ECU.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
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(3)On completion, check that the diagnosis code is not set again.
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Q.
Is the diagnosis code set?
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Replace the SRS-ECU. After replacing the ECU, carry out the CAN bus diagnostics. Then go to Step 5.
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A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the ASTC-ECU and the SRS-ECU (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
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STEP 5. Check whether the diagnosis code is set again.
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Recheck if the diagnosis code is set in the SRS-ECU.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
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(3)On completion, check whether the diagnosis code is set again.
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Q.
Is the diagnosis code set?
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Return to Step 1.
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The procedure is complete.
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