Hummer 24244544 Sensor Assembly, Automatic Transmission Input Speed

ISS and OSS sensors are located on the Jeff side of 4LB0-E and 4L85-E automatic transmissions; the ISS sensor near the front of the transmission and the OSS near the rear. ISS and OSS sensors are not used on 4L60-E and 4L65-E automatics, which are equipped instead with a single Vehicle Speed Sensor (VSS). Disconnect the cable from the negative battery terminal. Raise the vehicle and support it securely on jackstands. The ISS and OSS sensors are identical in appearance (and are replaced exactly the same way), so make sure that you've correctly identified the sensor that you wish to replace. Disconnect the electrical connector from the ISS or OSS sensor. To remove an ISS or OSS sensor, disconnect the electrical connector and remove the sensor mounting bolt. Place a drain pan underneath the sensor that you're going to replace. Remove the sensor mounting bolt and pull out the sensor. Installation is the reverse of removal. When you're done, check the transmission fluid level and add fluid as necessary.

There are a variety of electric-shift transfer cases on the models covered and several different combinations of speed sensors are available. The Vehicle Speed Sensor (VSS) sends information to the PCM for the driveability program and is located at the rear output shaft. The procedure for checking and replacement of the output shaft speed sensor is essentially the same as the procedure for the Vehicle Speed Sensor (VSS). A scan tool must be used to access speed sensor data and trouble codes.

The Vehicle Speed Sensor (VSS) is a permanent magnet generator mounted on the transmission. It is triggered by a toothed rotor on the transmission output shaft. As the output shaft rotates, the sensor produces an AC voltage, the frequency of which is proportional to vehicle speed. The PCM uses the sensor input signal for several different engine, transmission and radio control functions. The VSS signal also drives the speedometer on the instrument panel. A defective VSS can cause various driveabilily and transmission problems. To replace it, raise the vehicle and support it securely on jackstands. Disconnect the electrical connector from the VSS, which is located on the right side of the extension housing on automatic transmission models and on the left side of the extension housing on manual transmissions. Remove the mounting bolt and withdraw the VSS from the transmission case. Replace the sensor O-ring and lubricate it with clean transmission fluid. Installation is the reverse of removal.

On 4WD models, the VSS should be unscrewed using a deep socket.

The VSS signal drives the speedometer on the instrument panel.

The VSS is located on the right side of the extension housing.

This manual covers models with various electric-shift transfer cases and different combinations of speed sensors.

The VSS is located at the rear output shaft.

A scan tool is required to access speed sensor data and trouble codes.

This manual covers models with various electric-shift transfer cases and different combinations of speed sensors.

The second speed sensor is located at the rear output shaft.

The VSS is triggered by a toothed rotor on the transmission output shaft.