Gear Switches

WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

The automatic Transmission Fluid Pressure (TFP) manual valve position switch consists of six pressure switches. Five of the switches are normally-open, and determine gear range selection. The sixth switch is normally-closed, and detects Torque Converter Clutch (TCC) release fluid pressure. The TFP manual valve position switch also contains the automatic Transmission Fluid Temperature (TFT) sensor. These components are combined into one unit, attached to the control valve body. The PCM provides battery voltage on the three range signal circuits. By grounding one or more of the switches with fluid pressure from the manual shift valve, the PCM detects the selected gear range. When you disconnect the transmission electrical connector and the ignition switch is in RUN position, the ground potential for three range signals from the PCM will be removed, and an invalid gear range will be indicated.