Anti-Lock Brake System
BRAKE CONTROL: ANTI-LOCK BRAKE SYSTEM: C1237/37: Speed Sensor Rotor Faulty
DTC C1237/37 - Speed Sensor Rotor Faulty
DESCRIPTION
The skid control ECU measures the speed of each wheel by receiving signals from the speed sensor.
These signals are used for recognizing that all 4 wheels are operating properly.
Therefore, all wheel signals must be equal.
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT: Check the condition of each related circuit connector before troubleshooting Electronic Circuit Inspection Procedure.
PROCEDURE
1. CHECK TIRES
(a) Check the size and condition of all 4 tires Component Tests and General Diagnostics.
HINT: This DTC is output when tire deformation or a difference in tire size is detected.
OK:
The diameters of all 4 tires and air pressure are the same.
NG -- REPLACE TIRES SO THAT ALL 4 TIRES ARE THE SAME SIZE
OK -- Continue to next step.
2. INSPECT SPEED SENSOR AND SENSOR ROTOR SERRATIONS
(a) Disconnect the skid control ECU connector.
(b) Connect the oscilloscope to each speed sensor terminal of the skid control ECU connector.
Terminals:
(c) 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 output voltage becomes greater.
- When noise is identified in the waveform on the oscilloscope, the erratic signals are generated due to rotor scratches, looseness or foreign matter attached to the speed sensor.
(d) 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 or the wire harness.
(e) Connect the connector.
NG -- CHECK SPEED SENSOR ROTOR
OK -- Continue to next step.
3. RECONFIRM DTC
(a) Clear the DTC ABS (Antilock Brake System).
(b) Start the engine.
(c) Drive the vehicle at a speed of 20 mph (32 km/h) or more for 60 seconds or more.
(d) Check if the same DTC is recorded ABS (Antilock Brake System).
HINT: Reinstall the sensors, connectors, etc. and restore the vehicle to its prior condition before rechecking for DTCs.
Result:
B -- REPLACE BRAKE ACTUATOR ASSEMBLY
A -- CHECK FOR INTERMITTENT PROBLEMS (SYMPTOM SIMULATION)
4. CHECK SPEED SENSOR ROTOR
(a) Check the speed sensor rotor.
Front Speed Sensor Rotor: Removal
Rear Speed Sensor Rotor: Removal
OK:
No scratches or foreign matter on the rotors.
NOTICE: Check the speed sensor signal after the cleaning/replacement Test Mode Procedure.
NG -- CLEAN OR REPLACE SPEED SENSOR ROTOR
OK -- Continue to next step.
5. CHECK SPEED SENSOR TIP
(a) Remove each speed sensor.
(b) Check the speed sensor tip.
OK:
No scratches or foreign matter on the sensor tip.
NOTICE: Check the speed sensor signal after the cleaning/replacement Test Mode Procedure.
(c) Install speed sensor.
NG -- CLEAN OR REPLACE SPEED SENSOR
OK -- Continue to next step.
6. INSPECT EACH SPEED SENSOR
(a) Disconnect each speed sensor connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:
FRONT
REAR
(c) Connect the connector.
NOTICE: Check the speed sensor signal after replacement Test Mode Procedure.
NG -- REPLACE EACH SPEED SENSOR
OK -- Continue to next step.
7. CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU TO EACH SPEED SENSOR)
(a) Disconnect the skid control ECU connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:
FRONT
REAR
(c) Connect the connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (SKID CONTROL ECU TO EACH SPEED SENSOR)
OK -- Continue to next step.
8. RECONFIRM DTC
(a) Clear the DTC ABS (Antilock Brake System).
(b) Start the engine.
(c) Drive the vehicle at the speed of 20 mph (32 km/h) or more for at least 60 seconds.
(d) Check if the same DTC is recorded ABS (Antilock Brake System).
HINT: Reinstall the sensors, connectors, etc. and restore the vehicle to its prior condition before rechecking for DTCs.
Result:
B -- REPLACE BRAKE ACTUATOR ASSEMBLY
A -- CHECK FOR INTERMITTENT PROBLEMS (SYMPTOM SIMULATION)