Transmission Fluid Pressure Manual Valve Position Switch Assembly

A gear range sensing device called the Transmission Fluid Pressure (TFP) manual valve position switch assembly is used by the PCM to sense which gear range has been selected by the vehicle operator. The TFP manual valve position switch assembly is located on the valve body, and consists of 5 pressure switches combined into one unit. The PCM applies system voltage to the TFP manual valve position switch assembly on 3 separate wires. These 3 circuits are either grounded or open, depending on which gear range has been selected, and on which combination of the 5 switches gave pressure applied to them. See TFP MANUAL VALVE POSITION SWITCH LOGIC  table.

When the vehicle is in Park, with the ignition on and the engine off, the normal state of the TFP manual valve position switch assembly will be DRIVE 2. When the ignition is on and the engine is running, the normal state of the TFP manual valve position switch assembly is in PARK/NEUTRAL.

There are 2 possible combinations of the switches within the pressure switch manifold that do not represent an actual gear range. If the PCM detects either of these combinations, then a DTC sets.

The DTC P1810 sets when the TFP switch indicates the following:

• An illegal gear range.
• DRIVE 4, DRIVE 2 or REVERSE position before and after start-up.
• PARK/NEUTRAL with a ratio greater than 1.05.
• REVERSE with ratio indicating outside of REVERSE.
• DRIVE 4, DRIVE 3, DRIVE 2 or DRIVE 1 with ratio indicating REVERSE.

While DTC P1810 is present, the PCM assumes "D4" for shift pattern, sets line pressure to maximum, freezes shift adapts, and forces TCC on with 4th gear commanded.