Part 2

ENGINE CONTROL COMPONENTS

Fan Control

PCM Output State For Cooling Fan Speeds:

The hybrid vehicle uses a relay controlled fan system. The PCM monitors certain parameters (engine coolant temperature, vehicle speed, A/C ON/OFF status, and A/C pressure) to determine engine cooling fan needs. The PCM controls the fan operation through the low fan control (LFC), medium fan control (MFC), and high fan control (HFC) outputs.

For 3-speed fans, although the PCM output circuits are called low, medium, and high fan control (FC), cooling fan speed is controlled by a combination of these outputs. Refer to the table.

Fuel Injectors

Fuel Injectors:

CAUTION: Do not apply battery positive voltage (B+) directly to the fuel injector electrical connector terminals. The solenoids may be damaged internally in a matter of seconds.

The fuel injector is a solenoid operated valve that meters fuel flow to the engine. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open.

The fuel injector is normally closed, and is operated by VPWR from the electronic engine control (EEC) power relay. The ground signal is controlled by the PCM.

The injector is the deposit resistant injection (DRI) type and does not have to be cleaned. However, it can be flow checked and, if found outside of specification, a new fuel injector should be installed.

Fuel Pump (FP) Module

Electronic Returnless Fuel Pump (FP) Module:

The FP module is a device that contains the fuel pump and sender assembly. The fuel pump is located inside the FP module and supplies fuel through the FP module manifold to the engine and FP module jet pump. The jet pump continuously refills the reservoir with fuel, and a check valve located in the manifold outlet maintains system pressure when the fuel pump is not energized. A flapper valve located in the bottom of the reservoir allows fuel to enter the reservoir and prime the fuel pump during the initial fill.

Fuel Rail Pressure Temperature (FRPT) Sensor

Fuel Rail Pressure Temperature (FRPT) Sensor:

The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail and sends these signals to the PCM. The sensor uses the intake manifold vacuum as a reference to sense the pressure difference between the fuel rail and the intake manifold. A fuel return line to the fuel tank is not used in this type of fuel system. The relationship between fuel pressure and fuel temperature is used to determine the possible presence of fuel vapor in the fuel rail. Both pressure and temperature signals are used to control the speed of the fuel pump. The speed of the fuel pump maintains fuel rail pressure by keeping fuel in its liquid state. The dynamic range of the fuel injectors increases because of the higher rail pressure, which allows the injector pulse width to decrease.

Fuel Tank Isolation Valve (FTIV)

Fuel Tank Isolation Valve (FTIV):

The FTIV is a PCM-controlled solenoid that isolates the fuel tank from the rest of the EVAP system. The FTIV is a normally open valve allowing the flow of vapors from the fuel tank to the electronic EVAP canister purge valve and the EVAP canister. Whenever it is desired to isolate the fuel tank from the rest of the EVAP system, the PCM provides a variable duty cycle signal (between 0% and 100%) to the solenoid which controls the FTIV operation.

Fuel Tank Pressure (FTP) Sensor

Fuel Tank Pressure (FTP) Sensor:

The FTP sensor is used to measure the fuel tank pressure during the EVAP leak check monitor.

Generator Shut Down (GSDN)
The PCM keeps the generator motor inverter enabled by continuously toggling the GSDN output. Typical output frequency varies between 49 and 75 Hz at 50% duty cycle. The PCM also broadcasts a redundant not shutdown message to the TCM over the communication link. When a concern condition is detected, the PCM stops generating this frequency signal and broadcasts a shutdown message to the TCM over the communication link. The TCM then disables the generator motor inverter and sets an appropriate DTC. In the event of GSDN circuit failure, the PCM still broadcasts a not shutdown message but the hard wire signal frequency is out of expected range. The TCM then disables the generator motor inverter and sets the appropriate DTC.

Heated Oxygen Sensor (HO2S)

Typical Heated Oxygen Sensor (HO2S):

The HO2S detects the presence of oxygen in the exhaust and produces a variable voltage according to the amount of oxygen detected. A high concentration of oxygen (lean air/fuel ratio) in the exhaust produces a voltage signal less than 0.4 volt. A low concentration of oxygen (rich air/fuel ratio) produces a voltage signal greater than 0.6 volt. The HO2S provides feedback to the PCM indicating air/fuel ratio in order to achieve a near stoichiometric air/fuel ratio of 14.7:1 during closed loop engine operation. The HO2S generates a voltage between 0.0 and 1.1 volts.

Embedded with the sensing element is the HO2S heater. The heating element heats the sensor to temperatures of 800°C (1,400°F). At approximately 300°C (600°F) the engine can enter closed loop operation. The VPWR circuit supplies voltage to the heater and the PCM turns on the heater by providing the ground when the proper conditions occur. The heater allows the engine to enter closed loop operation sooner. The use of this heater requires that the HO2S heater control be duty cycled to prevent damage to the heater.

Heater Pump

Heater Pump:

The heater pump is required to maintain engine coolant flow to the heater core for passenger compartment heating when the engine is not running. The PCM commands the heater pump on by energizing the heater pump control relay (HPCR).

The pump is commanded on when the following conditions are met:
- The key is in the ON/START position.
- The engine coolant temperature is above a minimum threshold 0°C (32°F) nominal.
- The inferred ambient temperature is below a calibrated value 32°C (9O°F) nominal.
- The engine speed is below a calibrated threshold (nominal 4,000 RPM) including engine OFF.
- The climate control mode switch is in any position other than OFF.

The pump is off when the climate control mode switch is set to OFF.

Ignition Switch Position Run (ISP-R)
The ISP-R provides the PCM with a VBAT input signal from the ignition switch, indicating that the key is in either the ON or START position. When the operator turns the key to the OFF or ACC position, the internal combustion engine immediately ceases to provide power. The PCM coordinates the power down sequence by controlling the power sustain circuit and issuing the correct commands to shut down the electrical system in an orderly fashion. The PCM maintains power to the TCM through the power sustain circuit until the power down sequence is complete. The TBCM is always powered directly from the low voltage battery which permits wake-up when the vehicle is off.

Ignition Switch Position Run/Start (ISP-RS)
The ISP-RS provides the PCM with a VBAT input signal from the ignition switch, indicating the key is in the START position.

Immediate Shut Down (ISDN) 1 and 2
The TCM receives the redundant ISDN1 and ISDN2 signals from the high voltage traction battery. Under normal operating conditions the TCM monitors both ISDN circuits for low voltage battery voltage. If at any time during normal operation the TCM detects voltage drop on both ISDN circuits, the electronically controlled continuously variable transaxle (CVT) immediately stops delivering any torque, reduces operating voltage to under 50 volts, and discharges the high voltage capacitors. This action disables the vehicle until the key is cycled OFF and ON. The voltage drop on both ISDN circuits is usually a result of some other concern in the hybrid electric system, and DTCs indicating root cause may be stored in other modules. If the voltage drop is detected on only one of the ISDN circuits, the TCM continues its operation and stores the appropriate DTC. The voltage drop on only 1 of the ISDN circuits usually indicates an open ISDN circuit.

Intake Air Temperature (IAT) Sensor

Integrated Intake Air Temperature (IAT) Sensor:

The IAT sensor is integrated into the mass air flow (MAF) sensor. It is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and the resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.

A thermistor type sensor is considered a passive sensor. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in the total current flow.

Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The IAT provides air temperature information to the PCM. The PCM uses the air temperature information as a correction factor in the calculation of fuel, and ignition timing.

Knock Sensor (KS)
The KS is a tuned accelerometer on the engine which converts engine vibration to an electrical signal. The PCM uses this signal to determine the presence of engine knock and to retard spark timing.

Manifold Absolute Pressure (MAP) Sensor

Manifold Absolute Pressure (MAP) Sensor:

The MAP sensor uses a piezo-resistive silicon sensing element to provide a voltage proportional to the absolute pressure in the intake manifold.

The MAP sensor is part of the exhaust gas recirculation (EGR) system. The PCM uses information from the MAP sensor, throttle position (TP) sensor, mass air flow (MAF) sensor, cylinder head temperature (CHT) sensor and crankshaft position (CKP) sensor to determine how much exhaust gas is introduced into the intake manifold.

Mass Air Flow (MAF) Sensor

Mass Air Flow (MAF) Sensor:

The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire causes it to cool. This hot wire is maintained at 200°C (392°F) above the ambient temperature as measured by a constant cold wire. If the hot wire electronic sensing element must be replaced, then the entire assembly must be replaced. Replacing only the element may change the air flow calibration.

The current required to maintain the temperature of the hot wire is proportional to the volume of air flow. The MAF sensor then outputs an analog voltage signal to the PCM proportional to the intake air mass. The PCM calculates the required fuel injector pulse width in order to provide the desired air/fuel ratio.

The MAF sensor is located between the air cleaner and the throttle body inside the air cleaner assembly.

Motor Electronics Coolant Temperature (MECT) Sensor

Motor Electronics Coolant Temperature (MECT):

The MECT sensor is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and the resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature. A thermistor type sensor is considered a passive sensor. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor. The MECT provides motor electronics coolant system temperature information to the PCM. The PCM uses this information for determining when to activate the cooling system fans and indicate over-temperature.

Motor Electronics Cooling Pump (MECP)

Motor Electronics Cooling Pump:

Motor Electronics Coolant Flow:

The motor electronics cooling system is required to maintain an acceptable temperature for the transaxle and the DC/DC converter. The system temperature is monitored by the motor electronics coolant temperature (MECT) sensor, which is an input to the PCM. The PCM commands the MECP using the MECP relay. The MECP is commanded on whenever the traction battery contactors are closed. The coolant in the system flows in a loop from the MECP, to the DC/DC converter, to the top hose port of the motor electronics radiator, out of the motor electronics radiator bottom hose port, into the transaxle, and back into the MECP. The cooling system has a degassing system built into the loop that bleeds air/gases into the coolant reservoir.

Motor Shut Down (MSDN)
The PCM keeps the traction motor inverter enabled by continuously toggling the MSDN output. Typical output frequency varies between 49 and 75 Hz at 50% duty cycle. The PCM also broadcasts a redundant not shutdown message to the TCM over the communication link. When a concern condition is detected, the PCM stops generating this frequency signal and broadcasts a shutdown message to the TCM over the CAN communication link. The TCM then disables the traction motor inverter and sets an appropriate DTC. In the event of MSDN circuit failure, the PCM still broadcasts a not shutdown message but the hard wire signal frequency is out of expected range. The TCM then disables the traction motor inverter and sets the appropriate DTC.

Power Sustain Relay (PSR)

NOTE: The injectors and ignition coils are powered through a dedicated coil/injector relay so that the engine stops running when the key is turned to the OFF position.

The PSR is wired in parallel with the electronic engine control (EEC) power relay. The PCM and the TCM use the PSR to keep the modules powered. The PCM and TCM must be powered to complete the normal power down sequence, after the key is turned to the OFF or ACCY position. When the key is cycled from the OFF to ON or the ON/START position, the PCM smart driver grounds the PSR circuit. The PSR coil is energized and it closes the contacts of the PSR supplying the modules with the B+ power. The PSR coil stays energized after the key is turned to the OFF or the ACCY position until normal power down sequence is successfully completed. The PCM monitors the PSR output for an open and short circuit condition. The PSR circuit short to ground condition keeps the modules powered at all times and it may cause an excessive key off load on the low voltage system.

Throttle Actuator Control (TAC) Motor
The TAC is a DC motor controlled by the PCM (requires 2 wires). The gear ratio from the motor to the throttle plate shaft is 17:1. The motor housing is integrated into the main housing. Two springs are used; one is used to close the throttle (main spring) and the other is in a plunger assembly that results in a default angle when no power is applied. The force of the plunger spring is 2 times stronger than the main spring. The default angle is usually set to result in a top vehicle speed of 48 km/h (30 mph) Typically this throttle angle is 7 to 8 degrees from the hard stop angle. The closed throttle plate hard stop is used to prevent the throttle from binding in the bore (~0.75 degree). This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle.

Torque Of Generator-AC (TGAC) Signal
The TCM calculates an AC generator torque from an AC current measured by the current sensor which is located inside the transaxle. The TGAC is a 50% duty cycle signal which the TCM sends to the PCM over the TGAC circuit. The TCM also broadcasts a redundant generator torque message to the PCM over the communication link. The typical TGAC signal ranges from 200 Hz to 400 Hz, where 300 Hz is equal to 0 Nm (0 lb ft) of torque, 200 Hz is equal to 250 Nm (185 lb ft) of negative torque, and 400 Hz is equal to 250 Nm (185 lb ft) of positive torque. The PCM uses the generator torque value as an input to the energy management control strategy, the torque monitor strategy, and the regenerative brake torque limits strategy. In the event of TGAC circuit failure the PCM initiates limited operating strategy (LOS) shutdown mode which disables the vehicle. The PCM also stores an appropriate DTC.

Torque Of Motor-AC (TMAC) Signal
The TCM calculates an AC traction motor torque from an AC current measured by the current sensor which is located inside the transaxle. The TMAC is a 50% duty cycle signal which the TCM sends to the PCM using the TMAC circuit. TCM also broadcasts a redundant traction motor torque message to the PCM over the communication link. The typical TMAC signal ranges from 200 Hz to 400 Hz, where 300 Hz is equal to 0 Nm (0 lb ft) of torque, 200 Hz is equal to 250 Nm (185 lb ft) of negative torque, and 400 Hz is equal to 250 Nm (185 lb ft) of positive torque. Positive torque is perceived as vehicle acceleration and negative torque is perceived as braking. The PCM uses the traction motor torque value as an input to the energy management control strategy, the torque monitor strategy, and the regenerative brake torque limits strategy. In the event of TMAC circuit failure the PCM�initiates limited operating strategy (LOS) shutdown mode which disables the vehicle. The PCM also stores an appropriate DTC.

Transmission Range (TR) Sensor

Overview

Transmission Range (TR) Sensor:

The TR sensor communicates the gear selector position that 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 that 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 at the base of the gear selector assembly and the sensor shaft is moved by the selector.

TR Sensor and PCM Interface

Voltage Versus Angle And Gear Selected Chart:

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:
- 3 independent (TR-A1, TR-A2 and TR-A3) signals.
- 2 5-volt reference (TR-VREF1 and TR-VREF2) lines.
- 2 signal return (TR-RTN1 and TR-RTN2) lines.

The TR-A1 signal has a negative voltage slope, meaning the voltage decreases when the sensor angle increases. The typical TR voltage ranges from approximately 4.3 volts in the PARK position to approximately 0.6 volt in the LOW gear position. The TR-A2 and the TR-A3 signals both have a positive voltage slope. Voltages increase as the sensor angle increases. The typical voltage for the TR-A2 is about 1 volt in the PARK position to about 4.4 volts in the LOW gear position. The typical voltage for the TR-A3 is about 0.6 volts in the PARK position to about 4.05 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 in 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.

If the PCM detects a concern in one of TR signal inputs, it uses the other 2 TR signals to determine what gear the driver selects. If the PCM detects 2 or more TR signals that are invalid, the PCM:
- allows the vehicle to travel in DRIVE position 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 indicator.