C1237

BRAKE CONTROL: ANTI-LOCK BRAKE SYSTEM: C1237/37: Speed Sensor Rotor Faulty

DTC C1237/37 - Speed Sensor Rotor Faulty

DESCRIPTION

This code is output when a difference in tire size, foreign matter attached to a speed sensor tip or a sensor rotor, or a missing rotor serration is detected.
This code may be output when a malfunction in the terminal of the speed sensor circuit connector or wire harness is detected.






INSPECTION PROCEDURE

PROCEDURE

1. INSPECT TIRE
(a) Check the size and condition of all 4 tires.
HINT: This DTC is output when tire deformation or a difference in tire size is detected.

OK:
The diameter of all 4 tires and air pressure are the same.
NG -- REPLACE TIRES SO THAT ALL 4 TIRES ARE SAME IN SIZE
OK -- Continue to next step.
2. INSPECT SPEED SENSOR AND SENSOR ROTOR SERRATIONS
(a) INSPECTION USING OSCILLOSCOPE
(1) Disconnect the skid control ECU connector.





(2) Connect the oscilloscope to each speed sensor terminal of the skid control ECU connector.










(3) Check that a waveform is output when the tires are rotated (by the sensor circuit).
OK:
A waveform as shown in the figure should be output.
HINT:
- Each sensor circuit outputs the same waveform without noise.
- As vehicle speed (wheel rotation speed) increases, the width of the waveform narrows and the fluctuation in the output voltage becomes greater.
- When noise is identified in the waveform on the oscilloscope, error signals are generated due to rotor scratches, looseness or foreign matter attached to the speed sensor.

(4) Make sure that the waveform does not change while jiggling a connector or a wire harness.
OK:
The waveform does not change.
HINT: If the waveform changes while jiggling a connector or a wire harness, there may be a malfunction in the connector on the wire harness.

Result:






B -- REPAIR OR REPLACE HARNESS OR CONNECTOR (SKID CONTROL ECU TO SPEED SENSOR)
C -- CHECK OR REPLACE SPEED SENSOR AND SENSOR ROTOR
A -- Continue to next step.
3. RECONFIRM DTC
(a) Clear the DTC.
(b) Start the engine.
(c) Drive the vehicle at the speed of 20 mph (32 km/h) or more for 60 seconds or more.
(d) Check that the same DTC is recorded.
Result:






B -- REPLACE BRAKE ACTUATOR ASSEMBLY
A -- END