Lever Assembly/Manual Shaft Detent With Internal Mode Switch

WARNING: This page is about a different car, the 2003 Buick Regal and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

The lever assembly/manual shaft detent with Internal Mode Switch (IMS) is a sliding contact electrical switch assembly that corresponds to the PRNDL position selected. See Figure and Fig 1 . Each of the PRNDL positions has a unique ground pattern on four wires from the PCM.

The assembly consists of two major components:

The internal mode switch that consists of the housing, which makes up the stationary contacts, and the insulator, which makes up the moving contacts and is secured on the detent lever.
The lever assembly which consists of the manual shaft and the detent lever.

The range detection is accomplished by securing the moving contacts to the detent lever. When the driver selects a PRNDL position, the detent lever inside the transmission rotates. This rotates the insulator which in turn grounds the four wires in a unique pattern for each gear selection, corresponding to the PRNDL position selected. The IMS is electrically connected by five wires (four of which the PCM supplies voltage to and one wire that is a common ground) to the transmission that pass through connector.

Fig 1: Identifying Internal Mode Switch (IMS)

Courtesy of GENERAL MOTORS CORP.