Lever Assembly-Manual Shaft Detent with Internal Mode Switch

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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. 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, the insulator, which makes up the moving contacts and is secured on the detent lever. See Fig 1.
The lever assembly which consists of the manual shaft and a 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 pass through connector.

Fig 1: Identifying Manual Shaft Detent With Internal Mode Switch

Courtesy of GENERAL MOTORS CORP.