C1277
BRAKE CONTROL: ELECTRONICALLY CONTROLLED BRAKE SYSTEM: C1235/35: Foreign Object is Attached on Tip of Front Speed Sensor RH
DTC C1235/35 - Foreign Object is Attached on Tip of Front Speed Sensor RH
DTC C1236/36 - Foreign Object is Attached on Tip of Front Speed Sensor LH
DTC C1238/38 - Foreign Object is Attached on Tip of Rear Speed Sensor RH
DTC C1239/39 - Foreign Object is Attached on Tip of Rear Speed Sensor LH
DTC C1275/75 - Abnormal Change in Output Signal of Front Speed Sensor RH (Test Mode DTC)
DTC C1276/76 - Abnormal Change in Output Signal of Front Speed Sensor LH (Test Mode DTC)
DTC C1277/77 - Abnormal Change in Output Signal of Rear Speed Sensor RH (Test Mode DTC)
DTC C1278/78 - Abnormal Change in Output Signal of Rear Speed Sensor LH (Test Mode DTC)
DESCRIPTION
The speed sensor detects wheel speed and sends the appropriate signals to the ECU. These signals are used to control the ABS control system. The front and rear rotors have 48 serrations respectively.
When the rotors rotate, the magnetic field emitted by the permanent magnet in the speed sensor generates 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 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 C1275/75 to C1278/78 are output only in the Test Mode.
HINT:
- DTC C1235/35 is for the right front speed sensor.
- DTC C1236/36 is for the left front speed sensor.
- DTC C1238/38 is for the right rear speed sensor.
- DTC C1239/39 is for the left rear speed sensor.
WIRING DIAGRAM
INSPECTION PROCEDURE
NOTE: When replacing the skid control ECU, perform initialization of linear solenoid valve and calibration Initialization.
PROCEDURE
1. INSPECT SENSOR AND SENSOR ROTOR SERRATIONS
(a) Connect the oscilloscope to terminals S38-32 (FR+) and S38-22 (FR-), S41-28 (FL+) and S41-22 (FL-), S40-31 (RR+) andS40-23 (RR-) or S39-35 (RL+) andS39-27 (RL-) of the skid control ECU.
(b) Drive the vehicle at approximately 19 mph (30 km/h), and check the signal waveform.
OK:
A waveform as shown in the figure should be output.
- As the vehicle speed (wheel revolution speed) increases, a cycle 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 the speed sensor rotor's scratches, looseness or foreign matter attached to it.
Result:
D -- INSPECT SPEED SENSOR ROTOR
C -- INSPECT SPEED SENSOR TIP
B -- REPAIR OR REPLACE HARNESS OR CONNECTOR
A -- Continue to next step.
2. RECONFIRM DTC
(a) Clear the DTC Reading and Clearing Diagnostic Trouble Codes.
(b) Turn the ignition switch on.
(c) Drive the vehicle at the speed of 12 mph (20 km/h) or more for 60 seconds or more.
(d) Check that the same DTC is recorded Reading and Clearing Diagnostic Trouble Codes.
HINT: Reinstall the sensors, connectors, etc. and restore the previous vehicle conditions before rechecking for DTCs.
Result:
B -- REPLACE SKID CONTROL ECU
A -- END
3. INSPECT SPEED SENSOR TIP
(a) Remove the axle hub and speed sensor Removal, Removal).
(b) Check the sensor tip.
OK:
No scratches or foreign matter on the sensor tip.
NOTE: Check the speed sensor signal after the replacement Test Mode Procedure.
NG -- CLEAN OR REPLACE SPEED SENSOR
OK -- Continue to next step.
4. INSPECT SPEED SENSOR ROTOR
(a) Remove the axle hub and speed sensor rotor Removal, Removal).
(b) Check the sensor rotor serrations.
OK:
No scratches, missing teeth or foreign matter on the rotors.
HINT: If there is foreign matter in the rotor, remove it and check the output waveform after reassembly.
NOTE: Check the speed sensor signal after the replacement Test Mode Procedure.
NG -- CLEAN OR REPLACE SPEED SENSOR ROTOR
OK -- REPLACE SPEED SENSOR