GM Service Manual Online
For 1990-2009 cars only

Transmission Fluid Pressure (TFP) Switch Logic

Gear

TFP Switch States

TFP SW1

*TFP SW3

TFP SW4

TFP SW5

Park

High

Low

Low

Low

Reverse

Low

Low

Low

Low

Neutral

High

Low

Low

Low

Drive 1st - Engine Braking

High

High

Low

Low

Drive 1st

High

High

Low

High

Drive 2nd

High

Low

Low

High

Drive 3rd

Low

High

Low

High

Drive 4th

High

High

Low

Low

Drive 5th

Low

High

High

Low

Drive 6th

High

High

High

Low

Drive 6th (Possible additional gear state)

High

Low

High

Low

High = 12V (Switch Open or Pressurized)

Low = 0V (Switch Closed or No Pressure)

Note: All TFP switches are normally closed (NC)

*TFP switch 2 does not exist