Transmission Range Sensor: Operation
The Transmission Range Sensor (TRS) communicates shift lever position (SLP) to the PCM as a combination of open and closed switches. Each shift lever position has an assigned combination of switch states (open/closed) that the PCM receives from four sense circuits. The PCM interprets this information and determines the appropriate transmission gear position and shift schedule.
Since there are four switches, there are 16 possible combinations of open and closed switches (codes). Seven of these codes are related to gear position and three are recognized as "between gear" codes. This results in six codes which should never occur. These are called "invalid" codes. An invalid code will result on a DTC, and the PCM will then determine the shift lever position based on pressure switch data. This allows reasonably normal transmission operation with a TRS failure.