Speed Sensors

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Do not rotate the sensor in its retaining bracket. Changing the sensor/bracket orientation may cause improper operation.

There are three speed sensors typically required for use: the engine speed sensor, the turbine speed sensor, and the output speed sensor. The speed sensors provide RPM information to the TCM. The speed ratios between the various sensors allow the TCM to determine the transmission operating range. Speed sensor information is also used to control the timing of clutch apply pressures, resulting in the best possible shift quality. Hydraulic problems are detected by comparing the speed sensor information for the current gear range to that range's speed sensor information stored in the TCM memory. The speed sensors are variable reluctance devices that convert mechanical motion to an AC voltage. Each sensor consists of a wire coil wrapped around a pole piece that is adjacent to a permanent magnet. These elements are contained in a housing that is mounted adjacent to a rotating ferrous member. See Fig 1.

Fig 1: Identifying Speed Sensor

Courtesy of GENERAL MOTORS CORP.