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Home >> Lexus >> 2000 >> SC 400 >> Repair and Diagnosis >> Brakes >> Traction Control >> Anti-Lock - W/Traction Control >> Diagnostic Tests >> DTC 31-34: Speed Sensor Circuit >> Circuit Description

Circuit Description

Speed sensor detects wheel speed at each wheel and sends an AC signal to ABS/TRAC ECU as 48-tooth rotor passes a permanent magnet sensor. Frequency of AC signal changes with wheel speed. DTCs are set when ABS/TRAC ECU detects no input from speed sensors with vehicle traveling at 6 MPH or more for 15 seconds or more.

DTCs are also set when momentary interruption of speed sensor signal occurs at least 7 times during a driving cycle (after ignition is turned on and before ignition is turned off). DTCs are also set when speed sensor signals fluctuate abnormally with vehicle traveling at 12 MPH or more.

If trouble occurs in speed sensor circuit, ABS/TRAC ECU performs a fail safe function, turning off current to ABS solenoid relay and prohibiting ABS/TRAC control. Possible causes are:

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