Electronic Component Description

VEHICLE SPEED SENSOR





The vehicle speed sensor is a magnetic inductive pickup that relays vehicle speed information to the PCM. The PCM uses this information in order to control shift timing, line pressure, and TCC apply and release.
The vehicle speed sensor mounts in the case at the speed sensor rotor, which is pressed onto the differential. An air gap of 0.27 - 1.57 mm (0.011 - 0.062 inch) occurs between the sensor and the teeth on the speed sensor rotor. The sensor consists of a permanent magnet surrounded by a coil of wire. As the differential rotates, an AC signal is induced in the vehicle speed sensor. Higher vehicle speeds induce a higher frequency and a higher voltage measurement at the sensor.
Sensor resistance should measure between 981 - 1471 ohms at 20°C (68°F). Output voltage will vary with vehicle speed from a minimum of 0.5 volts AC at 25 RPM, to 200 volts at 1728 RPM.

AUTOMATIC TRANSMISSION INPUT SPEED SENSOR





The input speed sensor is a magnetic inductive pickup that relays input speed information to the PCM. The PCM uses A/T input speed information in order to control line pressure, TCC apply and release, and transmission shift patterns. This information is also used in order to calculate the appropriate operating gear ratios and TCC slippage.
The vehicle speed sensor mounts on the transmission case under the channel plate and next to the drive sprocket. An air gap of 0.08 - 2.12 mm (0.0032 - 0.834 inch) occurs between the sensor and the teeth on the drive sprocket. The sensor consists of a permanent magnet surrounded by a coil of wire. As the turbine shaft drives the drive sprocket, an AC signal is induced in the input speed sensor. Higher vehicle speeds induce a higher frequency and voltage measurement at the sensor.
Sensor resistance should measure between 893 - 1127 ohms at 20°C (68°F). Output voltage will vary with the vehicle speed from a minimum of 0.5 volts AC at 300 RPM to 200 volts at 6000 RPM.

1-2 AND 2-3 SHIFT SOLENOID VALVES








The shift solenoid valves are two identical, normally open, electronic exhaust valves that control upshifts and downshifts in all forward gear ranges. These shift solenoid valves work together in a combination of On and Off sequences in order to control the positions of the 1-2, 2-3, and 3-4 shift valve trains. The PCM monitors numerous inputs in order to determine the appropriate solenoid state combination and the transmission gear for the vehicle operating conditions.





The PCM energizes the shift solenoids by providing a ground to the solenoid's electrical circuit. This sends a current through the coil winding of the solenoid, thereby creating a magnetic field. The magnetic: field repels the plunger inside the solenoid. This seats the solenoid metering all against the fluid inlet port. This action prevents the exhaust of fluid through the solenoid and provides an increase in fluid pressure at the end of the shift valves. This fluid pressure initiates an upshift by moving the shift valves. Refer to the oil flow diagrams for a complete description of the hydraulic control of the shift valves for each gear range. Shift Solenoid resistance should measure between 19 - 24 ohms when measured at 20°C (68°F) and between 24 - 31 ohms when measured at 88°C (190°F). The shift solenoid valves should energize when the voltage is greater than 7.5 volts. The shift solenoid valves should de-energize when the voltage is less than one volt.

PRESSURE CONTROL SOLENOID VALVE





The Pressure Control Solenoid Valve (PC Sol. Valve) is a precision electronic pressure regulator that controls transmission line pressure based on current flow through its coil windings. As current flow is increased, the magnetic field which is produced by the coil moves the solenoid's plunger further away from the exhaust port. Opening the exhaust port decreases the output fluid pressure, which is regulated by the PC Sol. Valve. This ultimately decreases line pressure.
The PCM controls the PC Sol. Valve based upon various inputs including throttle position, fluid temperature, MAP sensor, and gear state. The PCM controls the PC Sol. Valve on a positive duty cycle at a fixed frequency of 292.5 Hz (cycles per second). Duty cycle is defined as the percentage of time when current flows through the solenoid coil during each cycle. A higher duty cycle provides a greater current flow through the solenoid. The high (positive) side of the PC Sol. Valve electrical circuit at the PCM controls the PC Sol. Valve operation. The PCM provides a ground path for the circuit, monitors average current, and continuously varies the PC Sol. Valve duty cycle in order to maintain the correct average current flowing through the PC Sol. Valve.





The Pressure Control Solenoid Valve resistance should measure between 3.5 - 4.6 ohms when measured at 20°C (68°F).

TORQUE CONVERTER CLUTCH PWM SOLENOID





The TCC solenoid is a normally closed, Pulse Width Modulation (PWM) solenoid which is used to control the apply and release of the converter clutch. The PCM operates the solenoid with a negative duty cycle at a fixed frequency of 32 Hz in order to control the rate of TCC apply/release. The solenoid's ability to ramp the TCC apply and release pressures results in a smoother TCC operation. When the vehicle's operating conditions are appropriate to apply the TCC, The PCM immediately increases the duty cycle to approximately 22%. The PCM then ramps the duty cycle up to a maximum of 98% in order to achieve full TCC apply pressure. The rate at which the PCM increases the duty cycle controls the TCC apply. Similarly, the PCM also ramps down the TCC solenoid duty cycle in order to control TCC release.
Some operating conditions prevent or enable TCC apply under various conditions. Refer to Automatic Transmission Fluid Temperature Sensor. Also, if the PCM receives a high voltage signal from the brake switch, signaling that the brake pedal has been depressed, the PCM immediately releases the TCC.
Minimum TCC duty cycle for EC3-equipped vehicles is 22% for maximum line pressure and 43% for minimum line pressure. The TCC PWM will typically be 40 - 60% at full apply. Your results may vary.

AUTOMATIC TRANSMISSION FLUID PRESSURE MANUAL VALVE POSITION SWITCH





The Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) is attached to the valve body, and consists of six fluid pressure switches. Three of the fluid pressure switches (PND4, Low, and Reverse) are normally open, while the other three (D3, D2, and TCC Release) are normally closed. These six switches indicate the position of the manual valve. The PCM uses this information in order to control line pressure, TCC apply, and release and shift solenoid operation.
The Release pressure switch is a normally closed pressure switch. This switch is used as a diagnostic tool in order to confirm that the TCC is actually Off when the PCM issues the command to turn the switch Off.





Each fluid pressure switch produces either an Open or a Ground to the PCM depending upon the presence of fluid pressure at the switches. The sequence of open and closed switches produces a combination of voltage readings that are monitored by the PCM. The PCM measures the TFP Val. Position Sw. signal voltage from each pin to ground and compares this voltage to a combination chart which is stored in PCM memory. If the PCM does not recognize the switch sequence, then a diagnostic code will be set as a result. A diagnostic code may also be set if the TFP Val. Position Sw. sequence indicates a gear range selection that conflicts with other sensory inputs to the PCM.
Resistance should be measured with the engine running. When the transmission pass-through connector is disconnected from the vehicle harness and the engine is running, then multiple diagnostic codes will be set. Clear these codes when you have finished with this procedure.

AUTOMATIC TRANSMISSION FLUID TEMPERATURE SENSOR





The temperature sensor is a negative temperature coefficient thermistor (temperature sensitive resistor) that provides information to the PCM regarding the transmission fluid temperature. The temperature sensor clips on to the valve body, and is replaced as a part of the A/T wiring harness. The sensor monitors pressurized main line pressure from the inside of the valve body in order to determine the operating temperature of the transmission fluid.
The internal electrical resistance of the sensor varies in relation to the operating temperature of the transmission fluid. The PCM sends a 5-volt reference signal to the temperature sensor and the PCM measures the voltage drop in the electrical circuit. A lower fluid temperature creates a higher resistance in the temperature sensor, thereby measuring a higher voltage signal.
The PCM measures this voltage as another input in order to help control line pressure, shift schedules, and TCC apply. when the transmission fluid temperature reaches 130°C (266°F), the PCM enters hot mode. Above this temperature the PCM modifies the transmission shift schedules and the TCC apply in an attempt to reduce the fluid temperature by reducing the transmission heat generation. During hot mode the PCM applies the TCC at all times in Third and Fourth gears. Also, the PCM performs the 2-3 and the 3-4 shifts earlier in order to help reduce fluid heat generation.
The PCM stays in hot mode until the temperature drops below 120°C (248°F).