Circuit Description

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The automatic transmission fluid pressure (TFP) manual valve position switch consists of three pressure switches. Two of the switches are normally-open, and determine gear range selection. The third 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 transmission control module (TCM) provides battery voltage on the two range signal circuits. By grounding one or more of the switches with fluid pressure from the manual shift valve, the TCM detects the selected gear range. When the transmission electrical connector is disconnected and the ignition is ON, the ground potential for the range signals from the TCM is removed, and an invalid gear range is indicated. Refer to Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic .

When the TCM detects PARK, NEUTRAL, or a drive gear with a REVERSE ratio, DTC P1818 sets. DTC P1818 is a type B DTC.