Engine Control Components

ENGINE CONTROL COMPONENTS

Transmission Range (TR) Sensor

Overview
The TR sensor communicates the gear selector position the driver selects to the PCM. The PCM determines a gear mode based on the TR input and the vehicle speed signal. The PCM then broadcasts a gear mode message over the communication link. The TCM uses the gear mode message to engage the transaxle in the gear the driver selected. The other control modules use the gear mode message to control the rear lamps or a brake shift interlock solenoid. The TR sensor is mounted on the transmission assembly and the sensor shaft is moved by the selector shaft.

Transmission Range (TR) Sensor:

TR Sensor and PCM Interface
The TR sensor is a linear potentiometer device that provides the PCM with a percentage of input voltage proportional to the rotational angle of the sensor shaft. The TR sensor consists of:
- two independent signals (TR-A1 and TR-A2)
- two 5 volt reference lines (TR-VREF1 and TR-VREF2)
- two signal return lines (TR-RTN1 and TR-RTN2)

The TR-A1 signal has a positive voltage slope, meaning the voltage increases when the sensor angle increases. The typical TR voltage ranges from approximately 0.7 volt in the PARK position to approximately 3.8 volts in the LOW gear position. The TR-A2 signal has a negative voltage slope. Voltage decreases as the sensor angle increases. The typical voltage for the TR-A2 is approximately 4.3 volts in the PARK position to approximately 1.2 volts in the LOW gear position.

The TR-VREF circuits are bussed together internal to the TR sensor, and both TR-RTN circuits are bussed together internal to the TR sensor. One of the TR-VREF and one of the TR-RTN circuits are dedicated signals from the PCM. This design of redundant signals protects against an open circuit condition.

Voltage Versus Angle And Gear Selected Chart:

If the PCM detects a concern in one of TR signal inputs, it uses the other TR signal to determine what gear the driver selects. If the PCM detects one or more TR signals that are invalid, the PCM:
- allows the vehicle to travel in the DRIVE or LOW gear position if the vehicle was driving forward at a significant speed when the concern was detected.
- allows the vehicle to travel in REVERSE gear if the vehicle was driving backwards at a significant speed when the concern was detected.
- broadcasts gear mode - NEUTRAL over the communication link when vehicle speed decreases to 8 km/h (5 mph).
- sets the DTC and illuminates the malfunction indicator lamp (MIL).

Universal Heated Oxygen Sensor (HO2S)
The universal HO2S, sometimes referred to as a wide band oxygen sensor, uses the typical HO2S combined with a current controller in the PCM to infer an air/fuel ratio relative to the stoichiometric air/fuel ratio. This is accomplished by balancing the amount of oxygen ions pumped into or out of a measurement chamber within the sensor. The typical HO2S within the universal HO2S is used to detect the oxygen content of the exhaust gas in the measurement chamber. The oxygen content inside the measurement chamber is maintained at the stoichiometric air/fuel ratio by pumping oxygen icons into and out of the measurement chamber. As the exhaust gasses get richer or leaner, the amount of oxygen that must be pumped in or out to maintain a stoichiometric air/fuel ratio in the measurement chamber varies in proportion to the air/fuel ratio. The amount of current required to pump the oxygen ions into or out of the measurement chamber is used to measure the air/fuel ratio. The measured air/fuel ratio is actually the output from the current controller in the PCM and not a signal that comes directly from the sensor.

The universal HO2S also uses a self-contained reference chamber to make sure an oxygen differential is always present. The oxygen for the reference chamber is supplied by pumping small amounts of oxygen ions from the measurement chamber into the reference chamber. The universal HO2S does not need access to outside air.

Part to part variance is compensated for by placing a resistor in the connector. This resistor is used to trim the current measured by the current controller in the PCM.

Embedded with the sensing element is the universal HO2S heater. The heater allows the engine to enter closed loop operation sooner. The heating element heats the sensor to a temperature of 780°C (1,436°F). The VPWR circuit supplies voltage to the heater. The PCM controls the heater on and off by providing the ground to maintain the sensor at the correct temperature for maximum accuracy.

Variable Voltage Controller
The variable voltage controller is located within the transaxle. The variable voltage controller is a bi-directional voltage boost converter that couples the high voltage traction battery to the transaxle's generator motor and traction motor. The variable voltage controller steps up voltage output to maximize motor and generator efficiency. If there is a concern, the transaxle control module (TCM) will bypass the variable voltage controller and set a diagnostic trouble code (DTC).