Code No.C1201:
Wheel speed sensor (FR) (signal short circuit)
caution
If there is any
problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis,
diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table .).
Before replacing the ECU, ensure that the communication circuit is normal.
OPERATION
A toothed ABS rotor generates a voltage pulse as it moves
across the pickup field of each wheel speed sensor.
The wheel speed sensor transmit the frequency of the pulses to the ASTC-ECU.
The hydraulic unit assembly (integrated with ASTC-ECU) modulates the amount of braking force
individually applied to each wheel cylinder.
DIAGNOSIS CODE SET CONDITION
Diagnosis code No.C1201 is set if any abnormal voltage from the wheel speed sensor is
detected without the outputs of the codes No.C1200 or C1202.
PROBABLE CAUSES
Current trouble
Damaged wiring harness and connectors
Teeth lack or clogging of the ABS rotor
Malfunction of the front hub assembly
Noise interference
Wheel speed sensor malfunction
ASTC-ECU malfunction
Past trouble
Carry out diagnosis with particular emphasis on wiring harness and
connector failures between ASTC-ECU and the wheel speed sensor. For diagnosis procedures, refer
to How to treat past trouble (GROUP 00 - How to Cope with Intermittent Malfunctions .).
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnosis
Use M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table .).
On completion, go to Step 2.
STEP 2. Diagnosis code recheck after resetting CAN bus lines
(1)Erase the diagnosis code.
(2)Drive the vehicle at 15 km/h or more.
note
The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 15 km/h
or higher.
Q.
Is the diagnosis code No.C1201 set?
Go to Step 3.
This diagnosis is complete.
STEP 3. M.U.T.-III diagnosis code
Check that the diagnosis codes No.C1200 or C1202 is also set.
Q.
Are the diagnosis codes No.C1200 or C1202 also set?
Perform the diagnosis for the diagnosis codes No.C1200 or C1202 (Refer to , .).
Go to Step 4.
STEP 4. M.U.T.-III data list
Check the following data list (Refer to .).
Item No.02: FR wheel speed sensor
Q.
Is the check result normal?
Go to Step 12.
Go to Step 5.
STEP 5. Check for wheel speed sensor (FR) installation
Check how the wheel speed sensor (FR) is installed correctly (Disconnection of wheel speed
sensor (FR), loose mounting bolt, etc.).
Q.
Is the check result normal?
Go to Step 6.
Reinstall the wheel speed sensor (FR) correctly (Refer to .).
Then go to Step 13.
STEP 6. Check for wheel speed sensor (FR) output current
Refer to .
Q.
Is the check result normal?
Go to Step 7.
Replace the wheel speed sensor (FR) (Refer to .).
Then go to Step 13.
STEP 7. Check the front hub for looseness.
note
If the wheel bearing or front hub or axle shaft bearing are loose, the gap between
the wheel speed sensor and ABS rotor may become excessive.
Check the front hub, which diagnosis code indicates, for looseness. (Refer to GROUP
26, On-vehicle service - Wheel bearing axial play check .).
Q.
Is the check result normal?
Go to Step 8.
Replace the front hub assembly (Refer to GROUP 26, Front axle hub assembly .).
Then go to Step 13.
STEP 8. Check the ABS rotor.
Check the ABS rotor (FR), which diagnosis code indicates, for foreign material or deformation.
Q.
Is the check result normal?
Go to Step 9.
If the ABS rotor (FR) is contaminated with foreign material, clean it. If the
front hub assembly is deformed, replace it (Refer to GROUP 26, Front axle hub assembly .).
Then go to Step 13.
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.).
Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table