Code No.C1521 Vehicle speed sensor input malfunction


caution
  • If the electric power steering-ECU sets diagnosis code No.C1521, diagnose the CAN bus lines. If there is any fault in the CAN bus lines, an incorrect diagnosis code may be set.
  • Whenever the ECU is replaced, ensure that the communication circuit is normal.




DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set in the following case:

  • If the system receives an abnormal vehicle speed signal and the microprocessor determines that the vehicle speed measurement system is defective.
    • Criteria for judging malfunction
    • The vehicle speed is 30 km/h or more and the vehicle speed signal is 0 km/h

PROBABLE CAUSES

  • Defective wire(s) or connector(s) in the wiring harness between the ABS-ECU and the wheel speed sensor
  • Defective wire(s) or connector(s) in the wiring harness between the TCL/ASC-ECU and the wheel speed sensor
  • Malfunction of the wheel speed sensor or vehicle speed detection encoder
  • Defective power supply to the ABS-ECU
  • Defective power supply to the TCL/ASC-ECU
  • Malfunction of the ABS-ECU
  • Malfunction of the TCL/ASC-ECU
  • Malfunction of the electric power steering-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
(1)Connect M.U.T.-III to the 16-pin diagnosis 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 check result normal?

Go to Step 2.

Repair the CAN bus line (Refer to GROUP 54C - CAN bus line Diagnostic flow ). Then go to Step 2.

STEP 2. M.U.T.-III other system diagnosis code

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Check that an ABS system or TCL/ASC system diagnosis code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is an ABS system diagnosis code set?

Diagnose the ABS or TCL/ASC (Refer to GROUP 35B - Troubleshooting - Check chart for diagnosis code or GROUP 35C - Troubleshooting - Check chart for diagnosis code ).

Go to Step 3.

STEP 3. Check whether the diagnosis code is reset.

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Recheck whether diagnosis code C1521 is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is diagnosis code C1521 set?

Replace the electric power steering-ECU (Refer to ). Then go to Step 4.

The malfunction is intermittent. 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 reset.

caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Recheck whether diagnosis code C1521 is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.
(7)Disconnect M.U.T.-III.

Q. Is diagnosis code C1521 set?

Replace the hydraulic unit (Integrated with ABS-ECU or TCL/ASC) (Refer to GROUP 35B - ABS - Hydraulic Unit or GROUP 35C - TCL/ASC - Hydraulic Unit ).

This diagnosis is complete.