RAM 3500 HD Truck 2WD L6-6.7L DSL Turbo (2008)
Transmission Position Switch/Sensor: Description and Operation
68RFE Automatic Transmission
Description
DESCRIPTION
The Transmission Range Sensor (TRS) is part of the solenoid module, which is mounted to the top of the valve body inside the transmission.
The Transmission Range Sensor (TRS) has five switch contact pins that:
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Determine shift lever position
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Supply ground to the Starter Relay in Park and Neutral only.
The TRS also has an integrated temperature sensor (thermistor) that communicates transmission temperature to the TCM and PCM.
Operation
OPERATION
The Transmission Range Sensor (TRS) communicates shift lever position to the TCM as a combination of open and closed switches. Each shift lever
position has an assigned combination of switch states (open/closed) that the TCM receives from four sense circuits. The TCM interprets this information
and determines the appropriate transmission gear position and shift schedule.
There are many possible combinations of open and closed switches (codes). Five of these possible codes correspond to valid gear position, there are two
codes for the neutral position and three are recognized as "between gear" codes. This results in many codes which should never occur. These are called
"invalid" codes. An invalid code will result in a DTC, and the TCM will then determine the shift lever position based on pressure switch data. This
allows reasonably normal transmission operation with a TRS failure.
