Speed Sensors

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Speed Sensors

Courtesy of GENERAL MOTORS CORP.

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

There are three speed sensors typically required for use with 1000 Series transmissions. They include 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 conditions are detected by comparing the speed sensor information, for the current range, to the range of the speed sensor information stored in 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.