Automatic Transmission Fluid Pressure Manual Valve Position Switch Assembly
The automatic transmission fluid pressure (TFP) manual valve position switch assembly is attached to the control valve body. This assembly contains three fluid pressure switches and the automatic transmission fluid temperature 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 release pressure switch is used as a diagnostic tool to confirm that the TCC is actually OFF when it has been commanded OFF by the 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 the switches. The sequence of open and closed switches produces a combination of voltage readings. The TCM monitors these readings.
The TCM measures TFP manual valve position switch signal voltage from each pin to ground and compares the voltage to a TFP manual valve position switch combination table stored in the TCM memory. If the TCM does not recognize the switch sequence, a diagnostic code will be set as a result. A diagnostic code may also set if the TFP manual valve position switch sequence indicates a gear range selection that conflicts with other sensory inputs to the TCM.
On hybrid applications there is a fourth pressure siwtch that is noramlly open. This switch is monitored by the ECM to determine if the transmission has line pressure from either the transmission or the auxiliary transmission pump.
| Range Indicator | Fluid Pressure | Circuit | ||
|---|---|---|---|---|
| REV | DR | B | C | |
| 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 |
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Valid combinations for circuits B and C are shown in the table. LOW means that the switch is grounded with a resistance less than 50 ohms at 0 volts; HI means that the switch is open with a resistance greater than 50 K ohms at 12 volts.
Note that resistance should be measured with the engine running. When the transmission's pass through connector is disconnected from the vehicle harness while the engine is running, multiple diagnostic codes will set. Clear these codes when you are finished with this procedure.