Code No.U0121 ABS/ASC CAN timeout
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- If diagnosis code No. U0121 is set, be sure to diagnose the CAN bus line.
- When replacing the ECU, always check that the communication circuit is normal.
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OPERATION
The clearance warning control unit sets diagnosis code No.U0121 when it cannot receive signals from the ASTC-ECU.
TROUBLE JUDGEMENT
If the communication with ASTC-ECU cannot be established for 2500 ms or more.
PROBABLE CAUSES
- Malfunction of CAN bas line
- Malfunction of ASTC-ECU power supply circuit
- Malfunction of ASTC-ECU
- Malfunction of clearance warning control unit
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics.
Use the M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting 
).
STEP 2. Check the M.U.T.-III Diagnosis code for other system.
Check if diagnosis code No. U0121 is set in the combination meter.
Q.
Is the diagnosis code set?
Go to Step 3.
Go to Step 4.
STEP 3. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the clearance warning control unit.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Check if the diagnosis code is set.
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Q.
Is the diagnosis code set?
Replace the ASTC-ECU (Refer to GROUP 35C - Hydraulic unit ).
A poor connection, open circuit, or other intermittent malfunction in the CAN bus line between the clearance warning control unit and the ASTC-ECU. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .)
STEP 4. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the clearance warning control unit.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Check if the diagnosis code is set.
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Q.
Is the diagnosis code set?
Replace the clearance warning control unit (Refer to ).
A poor connection, open circuit, or other intermittent malfunction in the CAN bus line between the clearance warning control unit and the ASTC-ECU. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .)