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



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.

STEP 9. Connector check: A-48 ASTC-ECU connector, A-125 front wheel speed sensor (RH) connector.

Q. Is the check result normal?
Go to Step 10.
Repair the defective connector. Then go to Step 13.

STEP 10. Voltage measurement at the A-48 ASTC-ECU connector
(1)Disconnect the A-48 ASTC-ECU connector, the A-125 front wheel speed sensor (RH) connector.
(2)Measure the voltage between the A-48 ASTC-ECU connector terminal No.7 and body earth.
OK: 1V or less

Q. Is the check result normal?
Go to Step 11.
Repair the harness wire. Then go to Step 13.

STEP 11. Resistance measurement at the A-48 ASTC-ECU connector
(1)Disconnect the A-125 front wheel speed sensor (RH) connector, and measure the resistance at the harness connector side.
(2)Disconnect the A-48 ASTC-ECU connector.
(3)Measure the resistance between the A-48 ASTC-ECU connector terminal No.7 and body earth.
OK: No continuity

Q. Is the check result normal?
Go to Step 12.
Repair the harness wire. Then go to Step 13 .

STEP 12. Check whether the diagnosis code is reset.
(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?
Replace the hydraulic unit (integrated with ASTC-ECU) (Refer to .). Then go to Step 13.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions .).

STEP 13. Check whether the diagnosis code is reset.
(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?
Return to Step 1.
This diagnosis is complete.