Scion 89413-32010 Sensor, Transmission Revolution

The Anti-lock Brake System (ABS) available on 1993 and later 80 series vehicles is designed to maintain vehicle steerability, directional stability, and optimum deceleration under severe braking conditions and on most road surfaces by monitoring the rotational speed of each wheel and controlling brake line pressure to prevent wheel lock-up. The actuator assembly includes the master cylinder, an electric hydraulic pump, and four solenoid valves, with the pump providing hydraulic pressure to charge the reservoirs that supply pressure to the braking system. Speed sensors located at each wheel generate electrical pulsations to indicate wheel rotational speed, with front sensors mounted to the steering knuckle and rear sensors bolted to the axle carriers. The ABS computer, mounted under the dashboard, processes information from the wheel speed sensors to control hydraulic line pressure and monitors the system for faults, illuminating an "ABS" light on the dashboard if a problem develops. The ABS system control unit features a self-diagnosis system that detects sensor malfunctions and alerts the driver through the ABS warning light, which should turn off when the engine starts unless a malfunction is present. Diagnostic codes can be accessed by turning the ignition key to the ON position and using a jumper wire to connect specific terminals in the data link connector, with the ABS light indicating the number of flashes corresponding to the diagnostic code. The accompanying tables and charts provide details on the codes for various malfunctions, and after diagnosis, trouble codes can be cleared by depressing the brake pedal multiple times, followed by removing the jumper wire and reinstalling the connector cap, with further action recommended if issues persist.

1. Loosen the wheel lug nuts, raise the vehicle, and support it securely on jackstands. Remove the wheel. 2. Turn the ignition key to the Off position. 3. Disconnect the electrical connector at the sensor. 4. Remove the mounting bolt and carefully pull the sensor out from the knuckle or rear axle assembly. 5. Installation is the reverse of the removal procedure. Tighten the mounting fastener securely. 6. Install the wheel and lug nuts, tightening them securely. Lower the vehicle and tighten the lug nuts to the specified torque.

To remove the VSS, simply disconnect the electrical connector and remove the sensor retaining bolt.

Coat the new O-ring with automatic transmission fluid (ATF).

To check the sensor output, raise the relevant wheel, disconnect the wiring to the ABS sensor, and connect the meter to it. Then, spin the wheel and check that the output voltage is between 1.5 and 2.0 volts, depending on the speed of the wheel.

The VSS produces voltage pulses that are monitored by the Powertrain Control Module (PCM). This information is used to help control the fuel and ignition systems as well as transaxle shifting.

To replace the VSS, first remove the air filter housing. Then, disconnect the electrical connector from the VSS. After that, remove the VSS from the transaxle. Replace the 0-ring by removing the 0-ring from the speed sensor. Finally, installation is the reverse of removal.

Both sensors are located on the left side of the transmission. The input speed sensor is at the front end, near the bellhousing, while the output speed sensor is at the rear, on the extension housing (for 2WD models) or the front left corner of the transfer case (for 4WD models).

Refitting is done in reverse order of the removal procedure.