C1278

DTC C1278/78 Abnormal Change in Output Signal of Rear Speed Sensor LH (Test Mode DTC)

DESCRIPTION

DTC Detection Condition:

The speed sensors detect wheel speed and transmit the signals to the ECU. These signals are used for control of the ABS control system. Each of the front and rear rotors have 48 serrations. When the rotors rotate, the magnetic field generated by the permanent magnet in the speed sensor induces an AC voltage.

Since the frequency of this AC voltage changes in direct proportion to the speed of the rotor, the frequency is used by the ECU to detect the speed of each wheel.

When foreign matter adheres to the speed sensor tip or speed sensor rotor, or the rotor teeth are chipped, these DTCs are output. An abnormal waveform input from the sensor determines these conditions. These DTCs may be detected when a malfunction occurs in the connector terminals or wire harness of the speed sensor circuit.

DTCs C1275/75 to C1278/78 can be deleted when the speed sensor sends a vehicle speed signal or the Test Mode ends. DTCs from C1275/75 to C1278/78 are output only in the Test Mode.

HINT:
- DTCs C1235/35 and C1275/75 are for the front speed sensor RH.
- DTCs C1236/36 and C1276/76 are for the front speed sensor LH.
- DTCs C1238/38 and C1277/77 are for the rear speed sensor RH.
- DTCs C1239/39 and C1278/78 are for the rear speed sensor LH.

Wiring Diagram:

Step 1-2:

Step 2(Continued)-3:

Step 4:

Step 5-6:

Step 6(Continued)-9:

Step 9(Continued):

INSPECTION PROCEDURE

NOTE: When replacing the brake actuator assembly, perform zero point calibration. Programming and Relearning

HINT: When C0200/31, C0205/32, C0210/33, or C0215/34 is output together with C1235/35, C1236/36, C1238/ 38, or C1239/39, inspect and repair the trouble areas indicated by C0200/31, C0205/32, C0210/33, or C0215/34 first.