Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Transaxle Fluid Pressure (TFP) Switch Assembly: Notes
The transaxle fluid pressure (TFP) switch assembly is attached to the control valve body. This assembly contains three fluid pressure switches and the transaxle fluid temperature (TFT) sensor.
Two of the fluid pressure switches are normally open. These are used to indicate the position of the manual valve. The TCM uses this information to control line pressure, TCC apply and release and shift solenoid operation.
The TCC pressure release switch is used as a diagnostic tool to confirm that TCC is actually OFF when it has been commanded OFF by TCM. This switch is normally closed.
Each fluid pressure switch produces either an open or a ground to the TCM depending on the presence of fluid pressure at switches. The sequence of open and closed switches produces a combination of voltage readings. The TCM monitors these readings.
The TCM measures TFP switch signal voltage from each pin to ground and compares voltage to a TFP switch combination table stored in TCM memory. If the TCM does not recognize TFP switch sequence, a diagnostic code will be set as a result. A diagnostic code may also set if the TFP switch sequence indicates a gear range selection that conflicts with other sensor inputs to the TCM.
| Range Indicator | Fluid Pressure | Circuit | ||
|---|---|---|---|---|
| REV | DR | B (1225) |
C (1226) |
|
| Park/Neutral | 1 | 1 | HI | HI |
| Reverse | 1 | 0 | HI | LOW |
| Overdrive | 0 | 1 | LOW | HI |
| Manual Third | 0 | 1 | LOW | HI |
| Manual Second | 0 | 1 | LOW | HI |
| Manual First | 0 | 1 | LOW | HI |
|
||||
Valid combinations for circuits B (1225) and C (1226) are shown in table. LOW means that the switch is grounded with a resistance less than 50 ohms at 0 volts; HI means that switch is open with a resistance greater than 50 K ohms at 12 volts.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.