DTC C1237/37 Speed Sensor Rotor Faulty

for Preparation Click here

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.

DTC No.	DTC Detecting Condition	Trouble Area
C1237/37	When any of the following is detected: Wheel speed difference between the wheels. Wheel sensor signal failure. ABS control continues for 60 sec. or more.	Brake actuator assembly (skid control ECU) Speed sensor rotor (Front) Rear axle hub and bearing assembly Speed sensor Speed sensor circuit Tire and wheel size Tire deformation

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

Check the condition of each related circuit connector before troubleshooting (Click here).

1.CHECK TIRES

Check the size and condition of all 4 tires (Click here).
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.

REPLACE TIRES SO THAT ALL 4 TIRES ARE THE SAME SIZE

OK

2.INSPECT SPEED SENSOR AND SENSOR ROTOR SERRATIONS

Disconnect the skid control ECU connector.

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

Terminals:

Connector	Circuit
A25-5 (FL+) - A25-6 (FL-)	Front left speed sensor
A25-10 (FR+) - A25-9 (FR-)	Front right speed sensor
A25-7 (RL+) - A25-17 (RL-)	Rear left speed sensor
A25-19 (RR+) - A25-8 (RR-)	Rear right speed sensor

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:
1. Each sensor circuit outputs the same waveform without noise.
2. As vehicle speed (wheel rotation speed) increases, the width of the waveform narrows and the output voltage becomes greater.
3. 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.

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.

Connect the connector.

Go to step 4

OK

3.RECONFIRM DTC

Clear the DTC (Click here).

Start the engine.

Drive the vehicle at a speed of 32 km/h (20 mph) or more for 60 seconds or more.

Check if the same DTC is recorded (Click here).
HINT:
Reinstall the sensors, connectors, etc. and restore the vehicle to its prior condition before rechecking for DTCs.

Result:

Condition
Proceed to
DTC is not output
A
DTC is output
B

REPLACE BRAKE ACTUATOR ASSEMBLY (Click here)

CHECK FOR INTERMITTENT PROBLEMS (SYMPTOM SIMULATION) (Click here)

4.CHECK SPEED SENSOR ROTOR

Check the speed sensor rotor.
Front Speed Sensor Rotor: (Click here)
Rear Speed Sensor Rotor: (Click here)
OK:
No scratches or foreign matter on the rotors.
NOTICE:
Check the speed sensor signal after the cleaning/replacement (Click here).

CLEAN OR REPLACE SPEED SENSOR ROTOR

OK

5.CHECK SPEED SENSOR TIP

Remove each speed sensor.

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 (Click here).

Install the speed sensor.

CLEAN OR REPLACE SPEED SENSOR

OK

6.INSPECT EACH SPEED SENSOR

Disconnect each speed sensor connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance:

FRONT:

Tester Connection	Condition	Specified Condition
A14-1 (FL+) - A14-2 (FL-)	Always	1.4 to 1.8 kΩ at 20°C (68°F)
A14-1 (FL+) - Body ground	Always	10 kΩ or higher
A14-2 (FL-) - Body ground	Always	10 kΩ or higher
A35-1 (FR+) - A35-2 (FR-)	Always	1.4 to 1.8 kΩ at 20°C (68°F)
A35-1 (FR+) - Body ground	Always	10 kΩ or higher
A35-2 (FR-) - Body ground	Always	10 kΩ or higher

REAR:

Tester Connection	Condition	Specified Condition
g1-1 (RL+) - g1-2 (RL-)	Always	Below 2.2 kΩ
g1-1 (RL+) - Body ground	Always	10 kΩ or higher
g1-2 (RL-) - Body ground	Always	10 kΩ or higher
f1-1 (RR+) - f1-2 (RR-)	Always	Below 2.2 kΩ
f1-1 (RR+) - Body ground	Always	10 kΩ or higher
f1-2 (RR-) - Body ground	Always	10 kΩ or higher

Connect the connector.
NOTICE:
Check the speed sensor signal after replacement (Click here).

REPLACE EACH SPEED SENSOR

OK

7.CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU TO EACH SPEED SENSOR)

Disconnect the skid control ECU connector.