Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic
| Gear Selector Position | Signal A | Signal B | Signal C |
|---|---|---|---|
| Park/Neutral | HI | LOW | HI |
| Reverse | LOW | LOW | HI |
| Drive 4 | HI | LOW | LOW |
| Drive 3 | HI | HI | LOW |
| Drive 2 | HI | HI | HI |
| Drive 1 | LOW | HI | HI |
| Invalid | LOW | HI | LOW |
| Invalid | LOW | LOW | LOW |
| (1) HI = Ignition voltage; LOW = 0 voltage. | |||
| (1) | HI = Ignition voltage; LOW = 0 voltage. |
Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic (1)
Transmission Fluid Checking Procedure
- Start the engine and operate the vehicle for 15 minutes or until the transmission fluid reaches an operating temperature of 82-93°C (180-200°F).
- Park the vehicle on a level surface.
- With your foot on the brake, move the shift lever through each gear range. Pause for about 3 seconds in each range, ending in Park.
- Apply the parking brake and let the engine idle for 3 minutes.
- Remove the transmission fluid level indicator. Wipe the indicator clean. Reinsert the indicator. Give the indicator a full twist in order to close.
- Wait 3 seconds and remove the indicator.
- Read both sides of the indicator. The fluid must be within the hot cross-hatched area using the lowest level reading.
Scheme 534
Scheme 535
Cooler Flow Check and Flushing Steps
- Machine Set-up
- Determine Minimum Flow Rate
- Back Flush
- Forward Flush
- Flow Test
- Code Recording Procedure
- Cleanup
- Tools Required
- Preparation
- Back Flush
- Forward Flush
- Flow Check
- Clean-up
Automatic Transmission Fluid Temperature Sensor
The automatic transmission fluid temperature (TFT) sensor is part of the automatic transmission fluid pressure (TFP) manual valve position switch. The TFT sensor is a resistor, or thermistor, which changes value based on temperature. The sensor has a negative-temperature coefficient. This means that as the temperature increases, the resistance decreases and as the temperature decreases, the resistance increases.
The PCM supplies a 5-volt reference signal to the TFT sensor and measures the voltage drop in the circuit. When the transmission fluid is cold, the sensor resistance is high and the PCM detects high signal voltage. As the fluid temperature warms to a normal operating temperature, the resistance becomes less and the signal voltage decreases. Refer to TFT Sensor Specifications for a complete comparison of sensor resistance, temperature and signal voltage.
The PCM uses the TFT sensor information to control shift quality and TCC application.
Scheme 536
The transmission range (TR) switch is part of the park/neutral position (PNP) and backup lamp switch assembly, which is externally mounted on the transmission manual shaft. The TR switch contains four internal switches that indicate the transmission gear range selector lever position. The PCM supplies ignition voltage to each switch circuit. As the gear range selector lever is moved, the state of each switch may change, causing the circuit to open or close. An open circuit or switch indicates a high voltage signal. A closed circuit or switch indicates a low voltage signal. The PCM detects the selected gear range by deciphering the combination of the voltage signals. The PCM compares the actual voltage combination of the switch signals to a TR switch combination chart stored in memory.
Scheme 537
The transmission electrical connector is an important part of the transmission operating system. Any interference with the electrical connection can cause the transmission to set diagnostic trouble codes or affect proper operation.
The following items can affect the electrical connection
- Bent pins in the connector from rough handling during connection and disconnection
- Wires backing away from the pins or coming uncrimped, in either the internal or the external wiring harness
- Dirt contamination entering the connector when disconnected
- Pins in the internal wiring connector backing out of the connector or pushed out of the connector during reconnection
- Transmission fluid leaking into the connector, wicking up into the external wiring harness and degrading the wire insulation
- Moisture intrusion in the connector
- Low pin retention in the external connector from excessive connection and disconnection of the wiring connector assembly
- Pin corrosion from contamination
- Damaged connector assembly
Remember the following points
- In order to remove the connector, squeeze the two tabs toward each other and pull straight up without pulling by the wires.
- Limit twisting or wiggling the connector during removal. Bent pins can occur.
- Do not pry the connector off with a screwdriver or other tool.
- Visually inspect the seals to ensure that they are not damaged during handling.
- In order to reinstall the external wiring connector, first orient the pins by lining up the arrows on each half of the connector. Push the connector straight down into the transmission without twisting or angling the mating parts.
- The connector should click into place with a positive feel and/or noise.
- Whenever the transmission external wiring connector is disconnected from the internal : harness and the engine is operating, DTCs will set. Clear these DTCs after reconnecting the external connector.
