Engine Controls - Description & Operation (Hybrid): Other Ford C-MAX II

VECI Decal

Each vehicle has a VECI decal containing emission control information that applies specifically to the vehicle and engine. The specifications on the decal are critical to repairing emissions systems.

Scheme 8

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Engine And Evaporative Emission System Information

Manufacturers must use a standardized system for identifying their individual engine families. The engine family group and the evaporative family name consists of 12 characters each.

Both the engine family group and the evaporative family name are listed in the box on the emission decal as indicated in the area marked as engine evaporative family information. The first line contains the engine size and the 12 character engine family group. The second line contains the 12 character evaporative family name information. Both the engine family group and the evaporative family name are specific to the vehicle. Please refer to the Engine Family Group and the Evaporative Family Name worksheet for decoding information.

Scheme 11

VECI ACRONYM DEFINITIONS

CARB: California Air Resource Board

CARB LEV: Low Emission Vehicle

CARB TLEV: Transitional Low Emission Vehicle

CARB ULEV: Ultra Low Emission Vehicle

CARB ZEV: Zero Emission Vehicle

EPA: Environmental Protection Agency

EVAP: Evaporative Emission

GVW: Gross Vehicle Weight

GVWR: Gross Vehicle Weight Rating, curb weight plus payload.

LDV: Light Duty Vehicle, generally passenger cars and light trucks under 6, 000 pounds GVWR.

MY: Model Year

OBD: On Board Diagnostic

ORVR: On Board Refueling Vapor Recovery

SULEV: Super Ultra Low Emission Vehicle

Tier 0: California and Federal regulations effective prior to Tier 1 phase in dates.

Tier 1: California regulations beginning with 1993 model year and Federal regulations beginning with 1994 model year.

LEV: Low Emission Vehicle

ZEV: Zero Emission Vehicle

PZEV: Partial Zero Emission Vehicle

ULEV: Ultra Low Emission Vehicle

ILEV: Inherently Low Emission Vehicle

Accelerator Pedal Position (APP) Sensor

There are two pedal position signals in the sensor. Both signals, APP1 and APP2, have a positive slope (increasing angle, increasing voltage), but are offset and increase at different rates. The two pedal position signals make sure the PCM receives a correct input even if one signal has a concern. The PCM determines if a signal is incorrect by calculating where it should be, inferred from the other signals. If a concern is present with one of the circuits the other input is used. There are two reference voltage circuits, two signal return circuits, and two signal circuits between the PCM and the APP sensor assembly. The pedal position signal is converted to pedal travel degrees (rotary angle) by the PCM. The software then converts these degrees to counts, which is the input to the torque based strategy. For additional information, refer to ELECTRONIC THROTTLE CONTROL (ETC) SYSTEM .

Scheme 12

Ambient Air Temperature (AAT) Sensor

The AAT sensor is a thermistor device in which resistance changes with temperature. The 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.

Thermistor type sensors are considered passive sensors. 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 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 AAT sensor provides ambient air temperature information to the PCM for the temperature sensor correlation tests. The PCM also communicates the AAT sensor information to all other modules on the controller area network (CAN).

Scheme 13

Brake Pedal Position (BPP) Switch

The BPP switch is a normally open switch that, when closed, sends a signal to the PCM when the brake pedal is applied. The PCM strategy uses this signal input to aid the PCM in determining the correct function and operation of the vehicle cruise control, the electronic throttle control (ETC), and the transmission and regenerative braking systems. The BPP switch is hardwired to the PCM and supplies positive battery voltage when the brake pedal is applied. When the brake pedal is released, the BPP switch opens and no battery voltage input is sent to the PCM.

Scheme 14

Brake Pressure Switch

The brake pressure switch is integrated with the brake pedal position (BPP) switch. When the brake pedal is applied, the normally closed brake pressure switch opens the circuit.

The normally closed brake pressure switch, along with the normally open BPP switch, is used by the PCM strategy for a brake pedal rationality test. The PCM strategy looks for each switch to change states when the brake pedal is applied and released. If a failure occurs in one or both of the brake pedal inputs a diagnostic trouble code is set and the PCM misfire on board diagnostic (OBD) monitor is disabled.

Camshaft Position 11 (CMP11) Sensor

The CMP11 sensor is a Hall effect sensor that detects the position of the camshaft. The CMP11 sensor identifies when piston number 1 is on its compression stroke. A signal is then sent to the PCM and used for synchronizing the sequential firing of the fuel injectors. The PCM also uses the CMP11 signal to select the correct ignition coil to fire.

Scheme 15

Coil On Plug (COP)

The COP is part of the distributorless ignition system. The COP eliminates the need for secondary spark plug wires which improves reliability. The COP is the source of the high voltage which is used to generate the spark by the spark plug. There is 1 COP for each cylinder. The COP is mounted directly to the spark plugs. The function of the COP is to convert low voltage into high voltage in excess of 40, 000 volts.

The COP consists of primary and secondary windings. The primary winding is energized by the VPWR circuit. The PCM coil driver circuit is connected to the primary winding as well. The secondary winding is connected to the spark plug. The current flowing through the primary winding generates the magnetic field across both windings. The PCM activates the coil driver circuit by opening it. The instant the circuit opens the magnetic field collapses, inducing current flow in the secondary winding.

The COP has three different modes of operation: engine crank, engine running, and CMP failure mode effects management (FMEM).

Scheme 16

Crankshaft Position (CKP) Sensor

The CKP sensor is a hall effect sensor mounted on the engine block adjacent to a trigger wheel located on the crankshaft. By monitoring the crankshaft mounted trigger wheel, the CKP is the primary sensor for ignition information to the PCM. The trigger wheel has a total of 58 teeth spaced 6 degrees apart with 2 empty spaces. As the crankshaft rotates, the CKP sensor produces a sharp square wave and it detects the missing teeth when the expected change in the output signal is not produced within the expected time duration. By monitoring the trigger wheel, the CKP sensor signal indicates the crankshaft position and speed information to the PCM. By monitoring the missing teeth, the CKP sensor is also able to identify piston travel in order to synchronize the ignition system and provide a way of tracking the angular position of the crankshaft relative to a fixed reference. The PCM also uses the CKP signal to calculate engine RPM, fuel timing, fuel quantity, duration of the fuel injection and to determine if a misfire has occurred by measuring rapid decelerations between trigger wheel teeth.

Scheme 17

Cylinder Head Temperature (CHT) Sensor

Note. If the CHT sensor is removed from the cylinder head for any reason it must be replaced with a new sensor.

The CHT sensor is a thermistor device in which resistance changes with the temperature. The resistance of a thermistor decreases as 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.

Thermistor type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so varying the resistance of the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor (pull-up resistor) in 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 CHT sensor is installed in the cylinder head and measures the metal temperature. The CHT sensor provides complete engine temperature information and is used to infer coolant temperature. If the CHT sensor conveys an overheating condition to the PCM, the PCM initiates a fail-safe cooling strategy based on information from the CHT sensor. A cooling system concern, such as low coolant or coolant loss, could cause an overheating condition. As a result, damage to major engine components could occur. Using both the CHT sensor and fail-safe cooling strategy, the PCM prevents damage by allowing air cooling of the engine and limp home capability. For additional information, refer to POWERTRAIN CONTROL SOFTWARE for Fail-Safe Cooling Strategy.

Scheme 18

Electric Exhaust Gas Recirculation (EEGR) Valve

The EEGR valve is a water cooled motor and valve assembly. The motor is commanded to move in 52 discrete steps as it acts directly on the EEGR valve. The position of the valve determines the rate of EGR. The internal spring works to close the valve against the motor opening force.

Typical EEGR Valve

Scheme 19

Electronic Throttle Body (ETB) Throttle Position Sensor

The ETB throttle position sensor has two signal circuits in the sensor for redundancy. The redundant ETB throttle position signals are required for increased monitoring. The first ETB throttle position sensor signal (TP1) has a negative slope (increasing angle, decreasing voltage) and the second signal (TP2) has a positive slope (increasing angle, increasing voltage). The two ETB throttle position sensor signals make sure the PCM receives a correct input even if one signal has a concern. There is one reference voltage circuit and one signal return circuit for the sensor. The reference voltage circuit and the signal return circuit is shared with the reference voltage circuits and signal return circuits used by the APP sensor. For additional information, refer to the description of the ELECTRONIC THROTTLE CONTROL (ETC) SYSTEM .

Scheme 20

Evaporative Emission (EVAP) Leak Detection Control Module

The EVAP leak detection control module is mounted behind the fuel tank, near the EVAP canister and consists of a vacuum pump, a pressure sensor, a 0.02" reference orifice and a switching valve. The vacuum pump is used to apply a vacuum across the reference orifice and to apply a vacuum on the EVAP system for the EVAP leak check monitor. The 0.02" reference orifice is used to obtain a reference check for leak detection every time the EVAP monitor runs. The pressure sensor is used to determine the vacuum level across the reference orifice and for the EVAP leak detection monitor. The EVAP leak detection control module is vented to atmosphere through the switching valve and allows for purging during engine operation and refueling.

Typical EVAP Leak Detection Control Module

Scheme 21

Evaporative Emission (EVAP) Purge Valve

The EVAP purge valve is located in the fuel vapor line near the top of the engine. The PCM controlled EVAP purge valve controls the flow of fuel vapors from the EVAP canister to the intake manifold during engine operation. The EVAP purge valve is a normally closed valve. The PCM outputs a duty cycle between 0% and 100% to control the EVAP purge valve.

Typical EVAP Purge Valve

Scheme 22

Evaporative Emission (EVAP) Vapor Blocking Valve

The EVAP vapor blocking valve is mounted behind the fuel tank, near the EVAP canister. The EVAP vapor blocking valve is a normally open valve allowing the flow of vapors from the fuel tank to the EVAP purge valve and the EVAP canister. The PCM closes the vapor blocking valve whenever it is desired to isolate the fuel tank from the rest of the EVAP system.

Typical EVAP Vapor Blocking Valve

Scheme 23

Fan Control

The PCM monitors certain parameters (such as engine coolant temperature, vehicle speed, A/C on/off status, A/C pressure) to determine engine cooling fan needs.

The PCM controls the fan speed and operation using a duty cycle output on the FCV circuit. The fan controller (located at or integral to the engine cooling fan assembly) receives the FCV command and operates the cooling fan at the speed requested (by varying the power applied to the fan motor).

FCV DUTY CYCLE OUTPUT FROM PCM (NEGATIVE DUTY CYCLE)

Fuel Injectors

Note. Do not apply battery positive (B+) voltage 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 a 12 volt source from the PCM relay. The ground signal is controlled by the PCM.

The injector is the deposit resistant injector (DRI) type and does not have to be cleaned. Install a new fuel injector if the flow is checked and found to be out of specification.

Typical Fuel Injector

Scheme 24

Fuel Tank Isolation Valve

The fuel tank isolation valve is mounted behind the fuel tank, near the EVAP canister. The fuel tank isolation valve is a PCM controlled solenoid that isolates the fuel tank from the rest of the EVAP system. The fuel tank isolation valve is a normally closed valve blocking the flow of vapors from the fuel tank to the EVAP purge valve and the EVAP canister. This prevents the canister from becoming saturated causing hydrocarbons (HC) to be released into the atmosphere in a situation where the engine does not run during a drive cycle. The PCM opens the fuel tank isolation valve during refueling. The fuel tank isolation valve will automatically open to relieve excess pressure or vacuum if the fuel tank pressure or vacuum reaches a maximum calibrated value.

Typical Fuel Tank Isolation Valve

Scheme 25

Fuel Tank Pressure (FTP) Sensor

The FTP sensor is used to measure the fuel tank pressure. For plug in vehicles, the FTP sensor is located in the fuel vapor line between the fuel tank and the fuel tank isolation valve. For all others, the FTP sensor is located in the fuel vapor line between the fuel tank and the vapor blocking valve.

Scheme 26

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

The HO2S heater is embedded with the sensing element. The heating element heats the sensor to a temperature of 800°C (1, 472°F). At approximately 300°C (572°F) the engine enters closed loop operation. The VPWR circuit supplies voltage to the heater. The PCM turns the heater ON by providing the ground when the correct conditions occur. The heater allows the engine to enter closed loop operation sooner. The use of this heater requires the HO2S heater control to be duty cycled, to prevent damage to the heater.

Scheme 27

Intake Air Temperature (IAT) Sensor

The IAT sensor is integrated into the mass airflow (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 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 sensor 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.

Scheme 28

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.

Scheme 29

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor measures intake manifold absolute pressure. The PCM uses information from the MAP sensor to measure how much exhaust gas is introduced into the intake manifold.

Scheme 30

Mass Airflow (MAF) Sensor

The MAF sensor provides a signal to the PCM proportional to the intake air mass. The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. The hot wire is maintained at a constant temperature above ambient. Air passing over the hot wire cools the wire. The current required to maintain the temperature of the hot wire is proportional to the airflow. The PCM calculates the required fuel injector pulse width in order to provide the desired air to fuel ratio.

The MAF sensor is a digital sensor that provides an output signal of varying frequency. The signals time period is proportional to the flow rate crossing the sensor. The greater the airflow the shorter the time period. The time period varies from 1480 microseconds at a low flow or idle condition, to 106 microseconds at a high flow rate condition.

The MAF/IAT sensor is located in the intake air tube between the air filter housing and the throttle body.

Motor Electronics Cooling System (MECS) Pump

The motor electronics cooling system is required to maintain an acceptable operating temperature for the TCM. The TCM commands the MECS pump and operation using the MECSP circuit. The pump (located near the radiator) receives the MECSP command. The MECS pump is commanded on for a calibrated time when the vehicle is first started to degas the MECS system. The coolant in the system flows in a loop from the MECS pump, to the TCM, and then into the MECS radiator bottom hose port, out of the top hose port of the MECS radiator, and back into the MECS pump. The cooling system has a degassing system that is connected in parallel between the MECS radiator and the MECS pump. The degassing system bleeds air or gases into the degas reservoir.

Scheme 31

Throttle Actuator Control (TAC) Motor

The TAC motor is a DC motor controlled by the PCM. The motor housing is integrated into the main housing. An internal spring is used to return the throttle plate to a default position. The default position is typically a throttle angle of 7 to 8 degrees from the hard stop angle. The closed throttle plate hard stop prevents the throttle from binding in the bore. This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle. For additional information, refer to the ELECTRONIC THROTTLE CONTROL (ETC) SYSTEM .

Transmission Range (TR) Sensor

The TR sensor is a linear potentiometer device that provides the PCM with an input voltage proportional to the gear selected. The PCM determines a gear mode based on the TR input. The PCM then broadcasts a gear mode message over the controller area network (CAN). The PCM uses the gear mode message to engage the transmission 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 located inside the transmission assembly.

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

1. 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.
2. allows the vehicle to travel in REVERSE gear if the vehicle was driving backwards at a significant speed when the concern was detected.
3. broadcasts gear mode - NEUTRAL over the communication link when vehicle speed decreases to 8 km/h (5 mph).
4. sets the DTC and illuminates the malfunction indicator lamp (MIL).

Scheme 32

Universal Heated Oxygen Sensor (HO2S)

The universal HO2S, sometimes referred to as a wideband oxygen sensor, uses the typical HO2S combined with a current controller in the PCM to infer an air to fuel ratio relative to the stoichiometric air to fuel ratio. This is accomplished by balancing the amount of oxygen ions pumped in or out of a measurement chamber within the sensor. The typical HO2S within the universal HO2S detects the oxygen content of the exhaust gas in the measurement chamber. The oxygen content inside the measurement chamber is maintained at the stoichiometric air to fuel ratio by pumping oxygen ions in 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 to fuel ratio in the measurement chamber varies in proportion to the air to fuel ratio. The amount of current required to pump the oxygen ions in or out of the measurement chamber is used to measure the air to fuel ratio. The measured air to 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 trims the current measured by the current controller in the PCM.

The universal HO2S heater is embedded with the sensing element allowing the engine to enter closed loop operation sooner. The heating element heats the sensor to a temperature of 780°C to 830°C (1, 436°F to 1, 526°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.

Scheme 33

Modifications to OBD Vehicles

Modifications or additions to the vehicle may cause incorrect operation of the OBD system. Aftermarket antitheft systems, cellular telephones, and radios must be carefully installed. Do not install these devices by tapping into or running wires close to the powertrain control system wires or components.

Fuel Pump Control Module

The fuel pump control module receives a duty cycle signal from the PCM and controls the fuel pump operation in relation to this duty cycle. The PCM requests low or high speed fuel pump operation depending on engine fuel demand. The fuel pump control module controls the fuel pump by switching the fuel pump power circuit on and off at the required duty cycle. The fuel pump control module sends diagnostic information to the PCM on the fuel pump monitor circuit. For additional information on the fuel pump control and the fuel pump monitor, refer to FUEL SYSTEM .

Ignition Switch Position Run (ISP-R)

The ISP-R circuit provides the PCM with a 12 volt input signal indicating the ignition is in the ON position. The ISP-R circuit is open when the when the vehicle is turned off, indicating to the PCM to begin the power down sequence.

Powertrain Control Module (PCM)

The center of the electronic engine control (EEC) system is a microprocessor called the PCM. The PCM receives input from sensors and other electronic components. Based on information received and programmed into its memory, the PCM generates output signals to control various relays, solenoids, and actuators. The hybrid vehicle uses a 128 pin PCM which has three separate electrical harness connectors.

Scheme 34

PCM Location

Refer to the Electronic Engine Controls article for the location of the PCM.

Powertrain Control Module (PCM) Keep Alive Memory (KAM)

The PCM stores information about vehicle operating conditions in the KAM and then uses this information to compensate for component variability. The KAM remains powered when the ignition is in the OFF position so the information is not lost. Refer to RESETTING THE KEEP ALIVE MEMORY (KAM) , for additional information.

Vehicle Buffered Power (VBPWR)

The VBPWR is a PCM supplied voltage source that supplies regulated voltage (10 to 14 volts) to vehicle sensors that run off 12 volts but cannot withstand VPWR voltage variations. It is regulated to VPWR minus 1.5 volts and is voltage limited to protect the sensors.

Vehicle Power (VPWR)

The VPWR is the primary source of PCM voltage, the VPWR is switched through the PCM power relay and is controlled by the PCM.

Reference Voltage (VREF)

The VREF is a positive voltage (about 5 volts) that is output by the PCM. This is a consistent voltage that is used by the three wire sensors.

Signal Return (SIGRTN)

The SIGRTN is a dedicated ground circuit used by sensors.

Power Ground (PWRGND)

The PWRGND is a dedicated ground circuit for VPWR voltage circuit.

Brake Over Accelerator

The brake over accelerator feature may not be active during low speed operating conditions. This enables unique drive maneuvers such as trailer tow, boat launch and retrieval or operation in hilly environments where the operator may require the application of both the accelerator pedal and the brake pedal during low speed maneuvering. The brake over accelerator feature will be active at speeds greater than 16 km/h (10 mph).

In the event the accelerator pedal becomes entrapped, such as by an object lodging the pedal, the brake over accelerator feature will reduce engine power when the brake pedal is applied.

The hybrid vehicles achieve a result similar to the brake over accelerator feature by reducing power if the brakes are applied while the accelerator pedal is pressed.

Operators that rest a foot on the brake pedal when also applying the accelerator pedal may activate the brake over accelerator feature. The brake activation is detected by the PCM from the electrical brake switch. In addition to brake over accelerator comments, the customer may bring the vehicle in for repair to address concerns such as a hesitation/stumble or a lack/loss of power. In the event of a hesitation/stumble or a lack/loss of power concern, carry out normal vehicle diagnostics for the appropriate symptom code. If the brake over accelerator feature is suspect, the BRKOVR_ACTION, BRKOVRD_POSS and DIST_BRKOVRD PIDs will display a brake over accelerator event occurred.

In the event the brake over accelerator feature is suspected as the cause of the customer concern, explain to the customer the details of the override system as described above. Additionally, make sure the customer is aware that resting a foot on the brake pedal while driving may cause the activation of this feature. This also results in activation of the brake lights on the vehicle while driving. For additional information refer to the Owners Literature.

Computer Controlled Shutdown

The PCM energizes the PCM power relay, by grounding the PCMRC circuit. After the ignition is in the OFF, ACC or LOCK position, the PCM stays powered up until the engine shutdown occurs and other conditions have been met.

The PCM initiates logic which will lead to powering down the PCM power relay. After this logic is initiated, the following conditions must be met for the PCM power relay to be depowered

1. The ignition is OFF.
2. The gear selector position is in PARK.
3. The EVAP leak check monitor is complete.
4. The vehicle speed is below a calibrated threshold.
5. The PCM power relay diagnostic is complete.
6. The electric water pump is OFF.

Deceleration Fuel Shut Off (DFSO)

During a DFSO event the PCM disables the fuel injectors. A DFSO event occurs during closed throttle deceleration; similar to exiting a freeway. This strategy improves fuel economy and allows for increased rear heated oxygen sensor (HO2S) concern detection.

Engine RPM Limiter

The PCM disables some or all of the fuel injectors whenever an engine RPM or vehicle over speed condition is detected. The purpose of the engine RPM or vehicle speed limiter is to prevent damage to the powertrain. The vehicle exhibits a rough running engine condition, and the PCM stores a diagnostic trouble code (DTC) P0219. Once the engine returns to the normal operating mode. No repair is required. However, the technician should clear the DTCs and inform the customer of the reason for the DTC.

Excessive wheel slippage may be caused by sand, gravel, rain, mud, snow, ice, or excessive and sudden increase in RPM while in NEUTRAL or while driving.

Fail Safe Cooling Strategy

The fail safe cooling strategy is only activated by the PCM when an overheating condition has been identified. This strategy provides engine temperature control when the cylinder head temperature exceeds certain limits. The cylinder head temperature is measured by the cylinder head temperature (CHT) sensor. For additional information about the CHT sensor, refer to ENGINE CONTROL COMPONENTS .

A cooling system failure, such as low coolant or coolant loss, could cause an overheating condition. As a result, damage to major engine components could occur. Along with a CHT sensor, the fail safe cooling strategy is used to prevent damage by allowing air cooling of the engine. This strategy allows the vehicle to be driven safely for a short time with some loss of performance when an overheat condition exists.

Engine temperature is controlled by alternating the number of disabled fuel injectors, allowing all cylinders to cool. When the fuel injectors are disabled, the respective cylinders work as air pumps, and this air is used to cool the cylinders. The more fuel injectors that are disabled, the cooler the engine runs, but the engine has less power.

A wide open throttle (WOT) delay is incorporated if the cylinder head temperature is exceeded during WOT operation. At WOT, the injectors function for a limited amount of time allowing the customer to complete a passing maneuver.

Before injectors are disabled, the fail safe cooling strategy alerts the customer to a cooling system problem by illuminating the instrument panel cluster (IPC) temperature light and setting DTC P1285. Depending on the vehicle, other indicators such as an audible chime or warning lamp, can be used to alert the customer of fail safe cooling. If overheating continues, the strategy begins to disable the fuel injectors, DTC P1299 is stored in the PCM memory, and a malfunction indicator lamp (MIL) illuminates. If the overheating condition continues and a critical temperature is reached, all fuel injectors are turned OFF and the engine is disabled.

Failure Mode Effects Management

Failure mode effects management (FMEM) is an alternate system strategy in the PCM designed to maintain engine operation if one or more sensor inputs fail.

When a sensor input is perceived to be out of limits by the PCM, an alternative strategy is initiated. The PCM substitutes a fixed value and continues to monitor the incorrect sensor input. If the suspect sensor operates within limits, the PCM returns to the normal engine operational strategy.

All FMEM sensors display a sequence error message on the scan tool. The message may or may not be followed by key ON, engine OFF (KOEO) or continuous memory DTCs when attempting key ON, engine running (KOER) self test mode.

Flash Electrically Erasable Programmable Read Only Memory (EEPROM)

The flash EEPROM is an integrated circuit within the PCM. This integrated circuit contains the software code required by the PCM to control the powertrain. One feature of the EEPROM is that it can be electrically erased and then reprogrammed without removing the PCM from the vehicle. If a software change is required to the PCM, the module no longer needs to be replaced, but can be reprogrammed using a scan tool.

Short Term Fuel Trim

If the heated oxygen sensors (HO2S) are warmed up and the PCM determines the engine can operate near stoichiometric air to fuel ratio (14.7:1 for gasoline), the PCM goes into closed loop fuel control mode. Since an oxygen sensor can only indicate rich or lean, the fuel control strategy must constantly adjust the desired air to fuel ratio rich and lean to get the oxygen sensor to switch around the stoichiometric point. If the times between switches are the same, then the system is actually operating at stoichiometry. The desired air to fuel control parameter is called short term fuel trim (SHRTFT1) where stoichiometry is represented by 0%. Richer (more fuel) is represented by a positive number and leaner (less fuel) is represented by a negative number. Normal operating range for short term fuel trim is +/- 25%. Sometimes the calibration can run the system slightly lean or rich of stoichiometry. This practice is referred to as using bias. For example, the fuel system can be biased slightly rich during closed loop fuel to help reduce NOx.

Values for SHRTFT1 may change a great deal on a scan tool when the engine is operated at different RPM and load points. This is because SHRTFT1 reacts to fuel delivery variability that can change as a function of engine RPM and load. Short term fuel trim values are not retained after the engine is turned off.

Long Term Fuel Trim

While the engine is operating in closed loop fuel, the short term fuel trim corrections can be learned by the PCM as long term fuel trim (LONGFT1) corrections. These corrections are stored in keep alive memory (KAM) in tables that are referenced by engine speed and load. Learning the corrections in KAM improves both open loop and closed loop air to fuel ratio control. Advantages include

1. short term fuel trim does not have to generate new corrections each time the engine goes into closed loop
2. long term fuel trim corrections can be used both while in open loop and closed loop modes

Long term fuel trim is represented as a percentage, just like short term fuel trim, however it is not a single parameter. There is a separate long term fuel trim value that is used for each RPM and load point of engine operation. Long term fuel trim corrections may change depending on the operating conditions of the engine (RPM and load), ambient air temperature, and fuel quality (% alcohol or oxygenates). When viewing the LONGFT1 PID, the values may change a great deal as the engine is operated at different RPM and load points. The LONGFT1 PID displays the long term fuel trim correction that is currently being used at that RPM and load point.

High Speed Controller Area Network (CAN)

The high speed CAN is based on SAE J2284, ISO-11898 and is a serial communication language protocol used to transfer messages between electronic modules. Two or more signals can be sent over one CAN circuit allowing two or more electronic modules to communicate with each other. This communication network operates at 500 kilobytes per second (kb/sec) and allows the electronic modules to share their information messages.

Included in these messages is diagnostic data that is output over the CAN+ and CAN-lines to the data link connector (DLC). The diagnostic data such as self-test DTCs or parameter identifiers (PIDs) can be accessed with the scan tool. Information on scan tool equipment is described in DIAGNOSTIC METHODS .

Failure Type Byte

The failure type byte is designed to describe the specific failure associated with the basic DTC. For example, a failure type byte of 1C means circuit voltage out of range, 73 means actuator stuck closed. When combined with a basic component DTC, it allows one basic DTC to describe many types of failures.

For example, P0110:1C-AF means intake air temperature (IAT) sensor circuit voltage out of range. The base DTC, P0110, means intake air temperature sensor circuit, while the failure type byte 1C means circuit voltage out of range. This DTC structure was designed to allow manufacturers to more precisely identify different kinds of faults without always having to define new DTC numbers.

The PCM does not use failure type bytes and always sends a failure type byte of 00 (no sub type information). This is because OBD-II regulations require manufacturers to use two byte DTCs for generic scan tool communications. Additionally, the OBD-II regulations require the two byte DTCs to be very specific, so there is no additional information that the failure type byte could provide.

A list of failure type bytes is defined by SAE J2012 but is not described here because the PCM does not use the failure type byte.

Status Byte

The status byte is designed to provide additional information about the DTC, such as when the DTC failed, when the DTC was last evaluated, and if any warning indication has been requested. Each of the eight bits in the status byte has a precise meaning that is defined in ISO 14229.

The protocol is that bit seven is the most significant and left most bit, while bit zero is the least significant and right most bit.

Multiplexing

The increased number of modules on the vehicle necessitates a more efficient method of communication. Multiplexing is a method of designating a system for sending two or more signals simultaneously over a single circuit. In an automotive application, multiplexing is used to allow two or more electronic modules to communicate simultaneously over a single media. Typically this media is a twisted pair of wires. The information or messages that can be communicated on these wires consists of commands, mode status, or data. The advantage of using multiplexing is to reduce the weight of the vehicle by reducing the number of redundant components and electrical wiring.

Multiplexing Implementation

The multiplexing can be implemented by using a communication language protocol such as CAN. Vehicle network protocols such as CAN allow module-to-module communication to become possible. This communication allows several modules to share information within the vehicle network. The hybrid vehicle uses a high-speed CAN protocol for its powertrain communication. For more information about the entire communication network, refer to the Module Communications article.

Vehicle Speed From The Anti-Lock Brake System (ABS) Module

The ABS module calculates wheel speed from the front two wheel speed sensors and sends this information to the PCM through the communication network.

Vehicle Speed From The TCM

The TCM calculates traction motor speed from the traction motor resolvers and combines it with (PCM stored) tire size and axle ratio data to determine vehicle speed. This calculation is then sent to the PCM over the communication network.

Vehicle Speed From Engine And Generator Speed

The TCM calculates generator speed from the generator resolvers and sends this information to the PCM. The PCM combines input information from the generator speed and engine speed along with tire size and gear ratio to calculate a vehicle speed.

The PCM strategy cross checks all the inputs to determine if they agree with one another.

Battery Energy Control Module (BECM)

Refer to the High Voltage Traction Battery article for more information on BECM and for BECM diagnostics.

High Voltage Cables

The high voltage cables connect the high voltage traction battery to the TCM and the electric A/C motor. The harness is orange and contains high voltage positive and negative wires.

High Voltage Interlock (HVIL) Circuit

Refer to the High-Voltage Traction Battery article for the high voltage interlock system description and diagnostics.

Hybrid Electric Indicators

The hybrid electric warning indicators alert the driver that a hybrid electric system concern is detected. There are 3 indicators dedicated to the hybrid electric system

1. over temperature indicator
2. powertrain malfunction indicator (wrench)
3. hazard indicator

Over Temperature Indicator

The over temperature indicator illuminates when the engine, TCM, or DC/DC converter detect an over temperature condition. If any of the temperatures exceed their threshold value, the fail safe cooling status changes status to ON, and the control module that detected the concern stores a DTC and broadcasts a controller area network (CAN) message to the instrument panel cluster (IPC), which illuminates the indicator. The over temperature indicator is turned OFF when the temperature returns below the threshold value.

Powertrain Malfunction Indicator (Wrench)

The powertrain malfunction indicator (wrench) illuminates when a concern within the hybrid electric system is detected and a repair is needed. When the concern is present, the control module that detected the concern stores the DTC and broadcasts a CAN message to the IPC which turns the indicator ON.

The powertrain malfunction indicator (wrench) is turned OFF when the concern is no longer present and the ignition is cycled. If the powertrain malfunction indicator (wrench) flashes at the once per second rate, it indicates that the vehicle is in the engine running diagnostic mode. Refer to DIAGNOSTIC MODES for engine running diagnostic mode. The powertrain malfunction indicator (wrench) illuminates for 3 seconds during IPC prove out when the ignition is cycled from the OFF to the ON position.

Hazard Indicator (Red Triangle)

The hazard indicator illuminates when a severe concern within the hybrid electric system is detected and continued use of the vehicle is likely to cause damage to the system or to the vehicle. When the concern is present, the control module detects, sets the DTC and broadcasts a CAN message to the IPC which turns the indicator ON.

The hazard indicator is turned OFF when the concern is no longer present and the ignition is cycled. If the hazard indicator flashes at the once per second rate, it indicates the vehicle is in the engine cranking diagnostic mode. Refer to DIAGNOSTIC MODES for engine cranking diagnostic mode.

Low Voltage Battery Power

The low voltage battery is used as a low voltage energy storage. The battery is charged by the DC/DC converter. Refer to the High Voltage Converter/Inverter article for more information on the DC/DC converter.

Transmission Control Module (TCM)

Note. The TCM is also known as the secondary on board diagnostic module C (SOBDMC). Select SOBDMC on the scan tool for access to TCM functions.

The microprocessor that controls operation of the transmission is called the TCM. The TCM is a stand alone module. The TCM receives a variety of controller area network (CAN) messages and hardwired signals from modules connected to the CAN. Based on information received, the TCM makes a decision on how to control the operation of the generator motor or the traction motor. In case of a concern, the TCM is able to detect and store the appropriate DTC. The DTCs can be retrieved from the TCM by carrying out an on demand or continuous memory self test. The TCM can be reprogrammed. The TCM controls the motor electronics cooling system pump as well as the electric auxiliary heater and transmission auxiliary oil pump (plug in vehicles only).

TCM Keep Alive Memory (KAM)

The TCM stores data in the KAM (a memory integrated circuit chip) about vehicle operating conditions, and then uses this data to compensate for component variability. The KAM remains powered when the ignition is turned OFF so the data is not lost.

Variable Voltage Controller

The variable voltage controller is located within the TCM. The variable voltage controller is a bi-directional voltage converter that couples the high voltage traction battery to the transmission's generator motor and traction motor. The variable voltage controller can step up voltage output to maximize motor and generator efficiency; and can also step down the high voltage bus voltage to the charge the high voltage battery. If there is a concern, the TCM bypasses the variable voltage controller and sets a DTC.

The VPWR is the primary source of TCM power. The VPWR is switched through the TCM power relay and is controlled by the TCM.

The VREF is a positive voltage (about 5 volts) that is output by the TCM. This is a consistent voltage that is used by the three wire sensors.

The SIGRTN is a dedicated ground circuit used by sensors.

The PWRGND is a dedicated ground circuit for VPWR voltage circuit.

Creep Mode

The hybrid electric system delivers torque to the wheels to mimic the creep mode normally found on vehicles equipped with an automatic transmission. The TCM commands a predetermined amount of torque to be delivered to the output shafts of the electronically controlled transmission. This torque is delivered from the combination of the internal combustion engine, the traction motor, or the generator motor. The maximum creep speed in forward or reverse direction is about 6 km/h (4 mph). The creep speed may vary slightly if ambient temperature, altitude, relative humidity, engine temperature, or weight of the vehicle changes.

Driving Modes

There are five fundamental operating modes in the hybrid electric system

1. series mode
2. electric mode
3. positive split mode
4. negative split mode
5. engine cranking mode

Series Mode

The system operates in this mode when the engine is running and the vehicle is not moving. This is the preferred mode whenever the high voltage traction battery is charging, passenger compartment temperature control, high voltage traction battery temperature control or catalyst warm up is necessary.

Electric Mode

The system operates in this mode when the vehicle is propelled by the electrical power stored in the high voltage traction battery. The torque is supplied to the output shafts by the traction motor. This is the preferred mode whenever the desired torque is low and can be produced more efficiently by the electrical system than the engine. The electric mode is also used in reverse because the engine can deliver torque only in a forward direction.

Electric Mode

Scheme 35

Positive Split Mode

The system operates in this mode when the engine is running and powering the generator motor which produces the electricity. The power from the engine is split between the path through the generator motor and the path to the output shafts of the vehicle. The electricity produced by the generator motor charges the high voltage traction battery or powers the traction motor. In this mode the traction motor can operate as a motor or as a generator to make up the difference between engine torque and desired torque at the wheels. This mode is preferred whenever the traction battery needs to be charged or at moderate loads at low speeds.

Positive Split Mode

Scheme 36

Negative Split Mode

The system operates in this mode when the engine is running but the generator motor is reducing the engine speed. This mode is never preferred but occurs if the engine is running, the vehicle speed is high, the high voltage traction battery is charged.

Negative Split Mode

Scheme 37

Engine Cranking Mode

The generator motor provides the engine cranking function to start or restart the internal combustion engine. When the PCM requests the engine cranking mode, the generator motor rapidly accelerates the engine speed up to about 950 RPM in about 0.3 seconds. When the engine speed reaches a calibrated speed the PCM commands the delivery of fuel and spark at the appropriate time.

Engine Cranking Mode

Scheme 38

Limited Operating Strategy (LOS) Modes

The PCM may initiate one or more of the LOS modes for some hybrid electric system concerns. The objective of the LOS modes are to manage vehicle operation after one or more of the following systems are disabled due to a concern

1. engine
2. transmission
3. high voltage traction battery
4. regenerative brake system

Some LOS modes limit the vehicle capability to a limp home condition. Other LOS modes fully disable the vehicle. The PCM initiates the appropriate LOS mode depending on the severity of the concern that was detected.

Normal Power Down Sequence

The TCM must conduct a normal power down sequence. Whenever the ignition is turned to the OFF or ACC position, modules powered up by the ISP-R circuit immediately shut down. However the PCM, TCM, and the battery energy control module (BECM) stay on, until the power down sequence is complete. The PCM and TCM stay powered by controlling their own dedicated power relays. The BECM is powered directly from the low voltage battery which permits wake-up function when the vehicle is off. During the power down sequence the TCM

1. requests the PCM to cut power to the injectors and ignition coils (engine shut down).
2. disables the high voltage inverters.
3. requests the BECM to disable the DC/DC converter.
4. requests the BECM to open the high voltage contactors.
5. discharges the high voltage inverter capacitors.
6. opens the TCM power relay.

If the power down sequence does not execute correctly, it is considered an abnormal shut down which may result in the PCM, the TCM and the BECM storing DTCs.

Power Up Sequence

The TCM conducts a power up sequence every time the ignition is turned from the OFF to the START position, if the gear selector is in PARK or NEUTRAL. During the power up sequence the TCM

1. initializes and begins controller area network (CAN) communications with the PCM and the BECM.
2. requests the BECM to close the high voltage contactors.
3. illuminates the green ready indicator indicating the vehicle is ready to drive in electric, gasoline, or a combination of electric and gasoline modes.
4. if required, requests the PCM to start the internal combustion engine. The internal combustion engine will not start if the gear selector is in NEUTRAL. The internal combustion engine starts if it is required for cabin heating, windshield defrost or the outside temperatures are low. The internal combustion engine also starts if the high voltage battery charge is low.

If a concern is detected during the power up sequence, the TCM may initiate LOS mode and store a DTC.

Regenerative Braking

The regenerative braking is a software strategy and is controlled by the anti-lock brake system (ABS) module, the TCM, and the BECM. Regenerative braking is the ability to capture and store a portion of the energy that would be lost as heat during a braking event. When the driver applies the brakes, the TCM determines how much negative torque (braking force) the traction motor should provide in addition to the friction brakes. Depending on the high voltage traction battery state of charge, the amount of negative torque provided by traction motor can vary between 0 and 100 percent. The traction motor then becomes a generator, which causes the energy to flow into the high voltage traction battery. The TCM strategy smoothly blends regenerative and friction brake effort to make the dual brake operation transparent to the driver.

Regenerative Braking

Scheme 39

Vehicle System Controller (VSC)

The PCM, the TCM and the BECM are connected to a high speed controller area network (CAN) to exchange information messages. The VSC is a software function integrated inside the TCM, and is responsible for vehicle system operation, generating and sending commands to initiate appropriate actions such as LOS modes when concern is detected. The TCM also stores DTCs along with the freeze frame PID related to the LOS action that was initiated.

MALFUNCTION INDICATOR LAMP (MIL)

The MIL notifies the driver the PCM has detected an on board diagnostic (OBD) emission related component or system concern. When this occurs, an OBD DTC sets.

1. The MIL is located in the instrument panel cluster (IPC) and is labeled CHECK ENGINE, SERVICE ENGINE SOON or the international standards organization (ISO) standard engine symbol.
2. The MIL is illuminated during the IPC prove out for approximately 4 seconds.
3. The MIL remains illuminated after IPC prove out if: an emission related concern and DTC exists. the PCM does not send a control message to the IPC.
4. If the MIL remains off during the bulb check, there is: an instrument cluster concern. an instrument cluster wiring concern.
5. To turn OFF the MIL after a repair, a reset command from the scan tool must be sent, or 3 consecutive drive cycles must be completed without a concern.
6. For any MIL concern, refer to «QT1 CARRY OUT THE NETWORK TEST»(ref-609000-S03592003642014041200000) .
7. If the MIL flashes at a steady rate, a severe misfire condition may exist.
8. The MIL flashes after a period of time with the ignition ON engine OFF, unless the OBD inspection/maintenance (I/M) readiness indicators indicate all of the OBD monitors have completed since the last keep alive memory (KAM) reset or since the PCM DTCs have been cleared.

Scheme 40

Catalytic Converter

A catalyst is a material that remains unchanged when it initiates and increases the speed of a chemical reaction. A catalyst also enables a chemical reaction to occur at a lower temperature. The concentration of exhaust gas products released to the atmosphere must be controlled. The catalytic converter assists in this task. It contains a catalyst in the form of a specially treated ceramic honeycomb structure saturated with catalytically active precious metals. As the exhaust gases come in contact with the catalyst, they are changed into mostly harmless products. The catalyst initiates and speeds up heat producing chemical reactions of the exhaust gas components so they are used up as much as possible.

Light Off Catalyst

As the catalyst heats up, converter efficiency rises rapidly. The point at which conversion efficiency exceeds 50% is called catalyst light off. For most catalysts this point occurs at 246°C to 301°C (475°F to 574°F). The light off catalyst is located close to the exhaust manifold and lights off faster and reduces emissions quicker than the catalyst located under the body. Once the catalyst lights off, it quickly reaches the maximum conversion efficiency for that catalyst.

Exhaust System

The purpose of the exhaust system is to convey engine emissions from the exhaust manifold to the atmosphere. Engine exhaust emissions are directed from the engine exhaust manifold to the catalytic converter through the front exhaust pipe. A universal HO2S is mounted on the front exhaust pipe before the catalyst. The catalytic converter reduces the concentration of CO, unburned HCs, and NO x in the exhaust emissions to an acceptable level. The reduced exhaust emissions are directed from the catalytic converter past another HO2S mounted in the rear exhaust pipe and then on into the muffler. Finally, the exhaust emissions are directed to the atmosphere through an exhaust tailpipe.

Underbody Catalyst

The underbody catalyst is located after the light off catalyst. The underbody catalyst is inline with the light off catalyst. For an exact configuration of the catalyst and exhaust system, refer to the Exhaust System article.

Exhaust Manifold/Runners

The exhaust manifold runners collect exhaust gases from the engine cylinders.

Exhaust Pipes

Exhaust pipes serve as guides for the flow of exhaust gases from the engine exhaust manifold through the catalytic converter and the muffler. The pipes are usually treated with an anti corrosive coating agent during manufacturing to increase the life of the product.

The HO2S provides the PCM with voltage and frequency information related to the oxygen content of the exhaust gas. For additional information on the HO2S, refer to ENGINE CONTROL COMPONENTS .

Muffler

The muffler reduces the level of noise produced by the engine, and it also reduces the noise produced by exhaust gases as they travel from the catalytic converter to the atmosphere. Mufflers are usually treated with an anti corrosive coating agent during manufacturing to increase the life of the product.

Evaporative Emission (EVAP) System

The EVAP system consists of an EVAP leak detection control module, EVAP canister, EVAP purge valve, fuel tank, capless fuel tank filler pipe, fuel tank isolation valve (plug in vehicles), vapor blocking valve (all others) fuel tank pressure (FTP) sensor, fuel vapor hoses, intake manifold hose assembly, and the PCM.

For plug in vehicles, the fuel tank side of the fuel tank isolation valve is normally sealed by the closed fuel tank isolation valve that blocks the flow of vapors from the fuel tank to the EVAP canister. This system only allows fuel vapors into the EVAP canister during refueling.

For all others, the normally open vapor blocking valve only isolates the fuel tank from the rest of the EVAP system as necessary for EVAP leak check monitoring.

During the EVAP leak check monitor, the PCM controls the EVAP leak detection control module to seal the EVAP canister from the atmospheric pressure by closing the switching valve and applying the target vacuum in the EVAP system by turning ON the vacuum pump. Operation of the system is as follows

1. The FTP sensor monitors the fuel tank pressure and continuously transmits an input signal to the PCM.
2. For plug in vehicles, the normally closed fuel tank isolation valve is a PCM controlled valve that blocks the flow of vapors from the fuel tank to the EVAP canister. The PCM opens the fuel tank isolation valve to allow fuel vapors to the EVAP canister during refueling. For all others, the normally open vapor blocking valve is a PCM controlled solenoid. The PCM closes the vapor blocking valve when it is necessary to isolate the fuel tank from the rest of the EVAP system for EVAP leak check monitoring.
3. The EVAP leak detection control module is used to seal the EVAP system from the atmosphere and apply a vacuum on the EVAP system for EVAP leak check monitoring. A vacuum pump inside the EVAP leak detection control module applies a vacuum on EVAP system as needed during the EVAP leak check monitor. The pressure sensor internal to the EVAP leak detection control module monitors the system during the EVAP leak check monitor.
4. The EVAP purge valve is used to control the purge flow during engine running conditions.
5. For plug in vehicles, the EVAP canister is used on the sealed EVAP system to collect fuel vapors during refueling only. For all others, the EVAP canister is used to collect fuel vapors during any vehicle conditions.
6. A valve inside the fuel tank mounted fuel vapor tube assembly prevents liquid fuel from entering the EVAP canister and the EVAP purge valve under any vehicle altitude, handling, or rollover condition.

Scheme 41

Electric Exhaust Gas Recirculation (EEGR) System

The EEGR system consists of an electric motor EGR valve integrated assembly, a PCM, and connecting wiring. The EEGR valve is activated by an electric stepper motor. Engine coolant is routed through the assembly. A manifold absolute pressure (MAP) sensor is also required. For additional information on the EGR system components, refer to ENGINE CONTROL COMPONENTS . Operation of the system is as follows

1. The EEGR system receives signals from the cylinder head temperature (CHT) sensor, throttle position (TP) sensor, mass airflow (MAF) sensor, crankshaft position (CKP) sensor, and the MAP sensor to provide information on engine operating conditions to the PCM. The engine must be warm, stable, and running at a moderate load and RPM before the EEGR system is activated. The PCM deactivates the EEGR during idle, extended wide open throttle (WOT), or whenever a concern is detected in an EEGR component or EGR required input.
2. The PCM calculates the desired amount of EGR for a given set of engine operating conditions.
3. The PCM in turn outputs signals to control the EEGR motor to move (advance or retract) a calibrated number of discrete steps. The electric stepper motor directly actuates the EEGR valve, independent of engine vacuum. The EEGR valve is commanded from 0 to 52 discrete steps to get the EGR valve from a fully closed to a fully open position. The position of the EGR valve determines the EGR flow.
4. A MAP sensor measures variations in manifold pressure as exhaust gas recirculation is introduced into the intake manifold. Variations in EGR being used correlate to the MAP signal (increasing EGR increases manifold pressure values).

Scheme 42

Mechanical Returnless Fuel System (MRFS) - Dual Speed

The dual speed MRFS uses a fuel tank with reservoir, the fuel pump, the fuel pump control module, the fuel pressure regulator, the fuel filter, the fuel supply line, the fuel rail, and fuel injectors. For additional information on the fuel system components, refer to ENGINE CONTROL COMPONENTS . Operation of the system is as follows

1. The fuel delivery system is enabled during crank or running mode once the PCM receives a crankshaft position (CKP) sensor signal.
2. The fuel pump logic is defined in the fuel system control strategy and executed by the PCM.
3. In the event of a collision, power to the fuel pump control module is disconnected. The body control module (BCM) will disable the fuel pump control module relay when it receives a crash event controller area network (CAN) message from the restraints control module (RCM).
4. The PCM commands a duty cycle to the fuel pump control module. The fuel pump control module reports diagnostic information to the PCM.
5. The fuel pump control module controls the voltage to the fuel pump (FP) based on the duty cycle request from the PCM. Voltage for the fuel pump is supplied by the PCM relay. For additional information refer to «Fuel Pump Control»(ref-608998-S23087981002014041200000) and «Fuel Pump Monitor»(ref-608998-S02400437252014041200000) .
6. The fuel injector is a solenoid operated valve that meters the fuel flow to each combustion cylinder. 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 a 12 volt source from the fuel pump relay. The ground signal is controlled by the PCM.
7. There are three filtering or screening devices in the fuel delivery system. For additional information refer to «FUEL FILTERS»(ref-608998-S27108134542014041200000) .
8. The FP module contains the fuel pump, the fuel pressure regulator, lifetime fuel filter and the fuel sender assembly. The fuel pressure regulator is attached to the FP module and regulates the pressure of the fuel supplied to the fuel injectors. The fuel pressure regulator controls the pressure of the clean fuel as the fuel returns from the fuel filter. The fuel pressure regulator is a diaphragm-operated relief valve. Fuel pressure is established by a spring preload applied to the diaphragm. The FP module is located in the fuel tank.

Scheme 43

Fuel Pump Control - Dual Speed MRFS

The FPC signal is a duty cycle command sent from the PCM to the fuel pump control module. The fuel pump control module uses the FPC command to operate the fuel pump at the speed requested by the PCM or to turn the fuel pump OFF. A valid duty cycle to command the fuel pump ON is in the range of 15 to 47%. The fuel pump control module doubles the received duty cycle and provides this voltage to the fuel pump as a percent of the battery voltage. When the ignition is turned ON, the fuel pump runs for about 1 second and is requested OFF by the PCM if engine rotation is not detected.

FUEL PUMP DUTY CYCLE OUTPUT FROM PCM

Fuel Pump Monitor (FPM) - Dual Speed MRFS

The fuel pump control module communicates diagnostic information to the PCM through the FPM circuit. This information is sent by the fuel pump control module as a duty cycle signal. The four duty cycle signals that may be sent are listed in the following table.

FUEL PUMP CONTROL MODULE DUTY CYCLE SIGNALS

Fuel Filters

The system contains three filtering or screening devices. Refer to Fuel Tank and Lines article, for the individual component locations.

1. The fuel intake filter or screen is a fine nylon mesh filter mounted on the intake side of the fuel pump. It is part of the assembly and cannot be repaired separately.
2. The filter/screen at the fuel rail port of the injectors is part of the fuel injector assembly and cannot be repaired separately.
3. The fuel filter assembly is located between the fuel pump and the fuel injectors. This filter is a lifetime fuel filter located in the fuel pump assembly that allows clean fuel to return to the fuel tank.

Internal Combustion Engine

The variable compression engine uses the Atkinson cycle for its operation.

Electronically Controlled Continuously Variable Transmission

The primary objective of the electronically controlled transmission is to deliver torque to the drive axles of the vehicle. The transmission applies torque from either the internal combustion engine or electrical energy from the high voltage traction battery. The electrical energy is converted into mechanical power by the traction motor and the generator motor. For additional information, refer to HYBRID ELECTRIC CONTROL SOFTWARE , operating modes.

The key electronically controlled transmission components are

1. planetary gear set
2. generator motor
3. traction motor
4. TCM

Planetary Gear Set

The planetary gear set is internal to the electronically controlled transmission. The planetary gear set includes a carrier, a sun gear, planet gears, and a ring gear. The engine is connected to the carrier, the generator motor is connected to the sun gear, and the traction motor is connected to the ring gear of the planetary gear set.

Generator Motor

The generator motor is a three phase permanent magnet AC motor connected to the sun gear of the planetary gear set. The generator power inverter is internal to the TCM and receives a DC current from the high voltage traction battery. The DC current is inverted to an AC current, which is controlled by the TCM. The generator is used as a starter for the internal combustion engine, charges the high voltage traction battery, and controls the engine speed.

Traction Motor

The traction motor is a three phase permanent magnet AC motor connected to the ring gear of the planetary gear set. The traction motor is connected to the drive wheels through a series of gears and rotates whenever the drive wheels rotate. The traction motor power inverter is internal to the SOBMDC and receives a DC current from the high voltage traction battery. The DC current is inverted to an AC current, which is controlled by the TCM. The traction motor delivers positive torque for the vehicle in the forward or reverse direction. The traction motor also provides negative torque during the regenerative braking to function as a generator.

High Voltage Traction Battery

Refer to the Module Communication article, for additional information on reprogramming the TCM.

The high voltage traction battery stores energy for later use by the traction motor and the generator motor. The high voltage traction battery is connected to the TCM with high voltage cables. The TCM provides both the traction motor and the generator motor with 3-phase AC power by separate high voltage cables. The traction motor uses the high voltage AC power to move the vehicle. The generator motor uses the AC power when it starts the internal combustion engine. The high voltage traction battery also provides energy to the DC/DC converter, which steps down the high voltage to maintain the low voltage system charge. Refer to the Charging System article, for more information on the charging system. Refer to the High Voltage Converter/Inverter article, for more information on the DC/DC converter.

Integrated Electronic Ignition System

The integrated electronic ignition system consists of a crankshaft position (CKP) sensor, coil on plug (COP), connecting wiring, and a PCM. For additional information on the ignition system components, refer to ENGINE CONTROL COMPONENTS . The COP integrated electronic ignition system eliminates the need for spark plug wires, but does require input from the camshaft position (CMP) sensor. Operation of the components are as follows

1. The CKP sensor indicates the crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted to the crankshaft. The COP integrated electronic ignition system uses the CMP sensor to identify the compression stroke of cylinder 1, and to synchronize the firing of the individual coils.
2. The PCM uses the CKP signal to calculate a spark target and the CMP signal to identify the TDC of compression of cylinder 1 to synchronize the firing of the individual coils.
3. The COPs receive their signal from the PCM to fire at a calculated spark target. The COP system fires only one spark plug per coil and only on the compression stroke.
4. The PCM processes the CKP signal and broadcasts the signal to the controller area network (CAN). The PCM also sends the signal to the TCM as a hardwired clean tachometer output (CTO) signal.

Scheme 44

Engine Crank/Engine Running

During engine crank the PCM fires two spark plugs simultaneously. Of the two spark plugs simultaneously fired, one is under compression and the other is on the exhaust stroke. Both plugs fire until the camshaft position is identified by a successful camshaft position 11 (CMP11) sensor signal. Once the camshaft position is identified, only the cylinder under compression is fired.

CMP Failure Mode Effects Management (FMEM)

During CMP FMEM the COP ignition works the same as during engine crank. This allows the engine to operate without the PCM knowing if cylinder 1 is under compression or exhaust.

Electronic Throttle Body (ETB)

The ETB has the following characteristics

1. The throttle actuator control (TAC) motor is a DC motor controlled by the PCM.
2. An internal spring is used to return the throttle plate to a default position. The default position is typically a throttle angle of 7 to 8 degrees from the hard stop angle.
3. The closed throttle plate hard stop is used to prevent the throttle from binding in the bore. This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle.
4. The required idle airflow is provided by the plate angle in the throttle body assembly. This plate angle controls idle, idle quality, and eliminates the need for an IAC valve.
5. There is one reference voltage and one signal return circuit between the PCM and the ETB. The reference voltage and the signal return circuits are shared with the reference voltage and signal return circuits used by the accelerator pedal position (APP) sensor. There are also two throttle position (TP) signal circuits for redundancy. The redundant TP signals are required for increased monitoring reasons. The TP1 signal has a negative slope (increasing angle, decreasing voltage) and the TP2 signal has a positive slope (increasing angle, increasing voltage). The TP2 signal reaches a limit of approximately 4.5 volts at approximately 45 degrees of throttle angle.

For additional information on the APP sensor, refer to ENGINE CONTROL COMPONENTS .

Electronic Throttle Control (ETC) System Strategy

The torque based ETC strategy was developed to improve fuel economy and to accommodate variable camshaft timing (VCT). This is possible by not coupling the throttle angle to the driver pedal position. Uncoupling the throttle angle (produce engine torque) from the pedal position (driver demand) allows the powertrain control strategy to optimize the fuel control while delivering the requested torque.

The ETC monitor system is distributed across two processors within the PCM: the main powertrain control processor unit (CPU) and a separate monitoring processor. The primary monitoring function is carried out by the independent plausibility check software, which resides on the main processor. It is responsible for determining the driver demanded torque and comparing it to an estimate of the actual torque delivered. If the generated torque exceeds driver demand by a specified amount, appropriate corrective action is taken.

ETC SYSTEM FAILURE MODE EFFECTS MANAGEMENT (FMEM)

Variable Camshaft Timing (VCT) System

The VCT system consists of an electric hydraulic positioning control solenoid, camshaft position 11 (CMP11) sensor and a trigger wheel. The CMP trigger wheel indicates the camshaft position signal. A crankshaft position (CKP) sensor provides the PCM with crankshaft positioning information in 10 degree increments.

Scheme 45

1. The PCM receives input signals from the intake air temperature (IAT), cylinder head temperature (CHT), CMP11, throttle position (TP), mass airflow (MAF), and CKP sensors to determine the operating conditions of the engine. At idle and low engine speeds with closed throttle, the PCM controls the camshaft position based on engine coolant temperature, engine oil temperature, intake air temperature, and mass airflow. During part and wide open throttle, the camshaft position is determined by engine RPM, load and throttle position. The VCT system does not operate until the engine is at normal operating temperature.
2. The VCT system is enabled by the PCM when the correct conditions are met.
3. The CKP signal is used as a reference for camshaft positioning.
4. The VCT11 solenoid valve is an integral part of the VCT system. The solenoid valve controls the flow of engine oil in the VCT actuator assembly. As the PCM controls the duty cycle of the solenoid valve, oil pressure and flow advances or retards the camshaft timing. Duty cycles near 0% or 100% represent rapid movement of the camshaft. Retaining a fixed camshaft position is accomplished by dithering (oscillating) the solenoid valve duty cycle. The PCM calculates and determines the desired camshaft position. The PCM updates the VCT11 solenoid duty cycle until the desired position is achieved. A difference between the desired and actual camshaft position represents a position error in the PCM VCT control loop. The PCM disables the VCT and places the camshaft in a default position if a concern is detected. A related DTC is also set when the concern is detected.
5. When the VCT11 solenoid is energized, engine oil is allowed to flow to the VCT actuator assembly which advances or retards the camshaft timing. One half of the VCT actuator is coupled to the camshaft and the other half is connected to the timing chain. Oil chambers between the 2 halves couple the camshaft to the timing chain. When the flow of oil is shifted from one side of the chamber to the other, the differential change in oil pressure forces the camshaft to rotate in either an advance or retard position depending on the oil flow.

AIR FUEL RATIO IMBALANCE MONITOR

The air fuel ratio imbalance monitor is an on board diagnostic strategy designed to monitor the cylinder to cylinder air fuel ratio.

1. The air fuel ratio imbalance monitor estimates the cylinder to cylinder difference using the universal heated oxygen sensor (HO2S) high frequency signal. The difference between two consecutive front HO2S signals is continuously monitored and a differential signal value is calculated. If the difference between two consecutive samples exceeds a calibrated threshold, a cylinder to cylinder deviation is estimated and the differential signal accumulation is calculated. The differential signal accumulation is calculated continuously after vehicle startup and during closed loop fuel conditions during a short calibrated RPM window. Typically the window has over 50 engine revolutions. The differential signal accumulation is then compared to a calibrated signal threshold. The counter is incremented if the threshold is exceeded. At the same time, the total RPM window counter calculates number of completed RPM windows. When the monitor completes a calibrated number of total RPM windows, the air fuel ratio imbalance index is calculated. The monitor index is a ratio of failed RPM windows over total RPM windows required to complete the monitor. If the monitor index exceeds the threshold value the test fails.
2. The malfunction indicator lamp (MIL) is activated after a concern is detected on 2 consecutive drive cycles.

Scheme 46

CATALYST EFFICIENCY MONITOR

The catalyst efficiency monitor uses the rear heated oxygen sensor (HO2S), after the catalyst, to infer the hydrocarbon (HC) efficiency based on the oxygen storage capacity of the catalyst. During monitor operation the PCM calculates the length of the signal while the sensor is switching. Under normal closed loop fuel conditions, high efficiency catalysts have significant oxygen storage. This makes the switching frequency of the rear HO2S very slow and reduces the amplitude, which provides for a shorter signal length. As the catalyst efficiency deteriorates due to thermal and chemical deterioration, its ability to store oxygen declines. The rear HO2S signal begins to switch more rapidly with increasing amplitude and signal length. The predominant failure mode for high mileage catalysts is chemical deterioration (phosphorus deposits on the front brick of the catalyst), not thermal deterioration.

Integrated Air Fuel Catalyst Monitor Method

The integrated air fuel catalyst monitor method is used as the on board strategy designed to monitor the oxygen storage capacity of the catalyst after a deceleration fuel shut off (DFSO) event. The monitor determines the amount of fuel needed to drive the catalyst to a rich condition when starting from an oxygen saturated, lean condition. The monitor is a measure of how much fuel is required to force the catalyst from a lean to a rich condition. The monitor runs during fuel reactivation following a DFSO event. The monitor completes after a calibrated number of DFSO monitoring events have occurred.

Cold Start Emission Reduction Component Monitor

The engine speed monitor and the spark timing monitor are carried out during the cold start emission reduction component monitor. The engine speed monitor checks the average difference between the actual and desired engine speeds. The spark timing monitor compares the average difference between desired and commanded spark to a calibratable threshold.

Engine Speed And Spark Timing Monitor

The system monitor and component monitor share the same entry conditions and monitor flow. During the first 15 seconds of a cold start, the monitor checks the entry conditions, counts time in idle, observes catalyst temperature, calculates the average difference between desired and actual engine speed, and calculates the average difference between desired and commanded spark.

If the expected change in catalyst temperature is large enough, the monitor then begins a waiting period of 300 seconds after engine start. This waiting period allows time to diagnose other components and systems that affect the validity of the test. During this waiting period, there are no constraints on drive cycle and the monitor cannot be disabled without turning the ignition OFF.

If the system monitor result falls below its threshold and all of the component monitor results are below their respective thresholds, the monitor determines if the idle time was sufficient. If the idle time was sufficient the test is considered to be a pass and the monitor is complete. If idle time was not sufficient, the monitor will not make a pass call and does not complete. This prevents tip-ins from resulting in false passes.

Engine Speed Monitor Entry Conditions

1. Barometric pressure of 76.2 kPa (22.5 in-Hg) or greater
2. Engine coolant temperature at start is between -17.8°C (35°F) and 37.8°C (100°F)
3. Catalyst temperature at start is between -17.8°C (35°F) and 51.7°C (125°F)
4. Fuel level is above 15%
5. Injector cutout torque reduction is inactive
6. Power take off (PTO) operation is disabled

Spark Timing Monitor Entry Conditions

1. Barometric pressure of 76.2 kPa (22.5 in-Hg) or greater
2. Engine coolant temperature at start is between -17.8°C (35°F) and 37.8°C (100°F)
3. Catalyst temperature at start is between -17.8°C (35°F) and 51.7°C (125°F)
4. Fuel level is above 15%
5. Injector cutout torque reduction is inactive
6. PTO operation is disabled

Cold Start Variable Cam Timing (VCT) Monitor

If the VCT phasing is used during a cold start to improve catalyst heating, the VCT system checks the functionally by monitoring the closed loop camshaft position error correction. If the correct camshaft position cannot be maintained and the system has an advance or retard error greater than the calibrated threshold, a cold start emission reduction VCT control concern is indicated.

1. DTC: P052A Cold start camshaft position timing over-advanced (Bank 1)
2. DTC: P052B Cold start camshaft timing over-retarded (Bank 1)
3. Monitor execution: Continuous
4. Monitor sequence: None
5. Monitoring duration: 5 seconds

Cold Start Emission Reduction System Monitor

The PCM uses the cold start emission reduction system monitor to calculate the actual catalyst warm up temperature during a cold start. The actual catalyst warm up temperature calculation uses measured engine speed, measured air mass and commanded spark timing inputs to the PCM. The PCM then compares the actual temperature to the expected catalyst temperature. The expected catalyst temperature calculation uses desired engine speed, desired air mass and desired spark timing inputs to the PCM. The difference between the actual and expected temperatures is reflected in a ratio. This ratio is a measure of how much loss of catalyst heating occurred over the period of time and when compared with a calibrated threshold it helps the PCM to determine if the cold start emission reduction system is working correctly. This ratio correlates to tailpipe emissions, and a malfunction indicator lamp (MIL) illuminates and a DTC sets when the calibrated threshold is exceeded. The monitor is disabled if a concern is present in any of the sensors or systems used for expected catalyst temperature model calculation.

Cold Start Emission Reduction System Monitor Entry Conditions

1. Barometric pressure is above 74.5 kPa (22 in-Hg)
2. Engine coolant temperature at the start of the monitor is between 1.67°C (35°F) and 37.78°C (100°F)
3. Catalyst temperature at the start of the monitor is between 1.67°C (35°F) and 51.67°C (125°F)
4. Fuel level is above 15%
5. Injector cutout torque reduction is inactive

COMPREHENSIVE COMPONENT MONITOR (CCM)

The CCM detects concerns in any powertrain electronic component or circuit that provides input or output signals to the powertrain control module (PCM) that can affect emissions and is not monitored by another on board diagnostic (OBD) monitor. Inputs and outputs are, at a minimum, monitored for circuit continuity or correct range of values. Where feasible, inputs are checked for rationality, and outputs are also checked for correct functionality.

The CCM covers many components and circuits and tests them in various ways depending on the hardware, function, and type of signal. For example, analog inputs such as the cylinder head temperature (CHT) sensor or the intake air temperature (IAT) sensor are typically checked for opens, shorts, and out of range values. This type of monitoring is carried out continuously. Some digital inputs like crankshaft position or camshaft position rely on rationality checks to see if the input value makes sense at the current engine operating conditions. These types of tests may require monitoring several components and can be carried out only under appropriate test conditions.

Outputs such as the evaporative emission (EVAP) purge valve are checked for opens and shorts by monitoring a feedback circuit or smart driver associated with the output. Other outputs, such as relays, require additional feedback circuits to monitor the secondary side of the relay. Some outputs are also monitored for correct function by observing the reaction of the control system to a given change in the output command. Some tests can be carried out only under appropriate test conditions.

The following is an example of some of the input and output components monitored by the CCM. The components monitor may belong to the engine, ignition, air conditioning, or any other PCM supported subsystem.

1. Inputs: Mass airflow (MAF) sensor, intake air temperature (IAT) sensor, cylinder head temperature (CHT) sensor, crankshaft position (CKP) sensor, camshaft position 11 (CMP11) sensor.
2. Outputs: EVAP purge valve, variable camshaft timing 11 (VCT11) solenoid.
3. The CCM is enabled after the engine starts and is running. A diagnostic trouble code (DTC) is stored in keep alive memory (KAM) and the malfunction indicator lamp (MIL) is illuminated after two drive cycles when a concern is detected. Many of the CCM tests are also carried out during the on demand self test.

Scheme 47

ELECTRIC EXHAUST GAS RECIRCULATION (EEGR) SYSTEM MONITOR

The EEGR system monitor is an on board strategy designed to test the integrity and flow characteristics of the EGR system. The EEGR system monitor consists of an electrical and functional test that checks the stepper motor and the EEGR system for correct flow. The powertrain control module (PCM) controls the EEGR valve by commanding from 0 to 52 discrete increments or steps to get the valve from the fully closed position to the fully open position. The stepper motor electrical test is a continuous check of the 4 electric stepper motor coils and circuits to the PCM. A concern is indicated if an open circuit, short to voltage, or short to ground has occurred in one or more of the stepper motor coils or circuits for a calibrated period of time. If a concern has been detected, the EEGR system is disabled, setting a DTC. Additional monitoring is suspended for the remainder of the drive cycle, or until the next engine start.

The intake manifold pressure is higher when EGR is flowing than when it is not flowing. When the exhaust gas is delivered into the intake manifold, the manifold absolute pressure (MAP) sensor reading increases. The detection of EGR flow occurs by monitoring this increase in pressure. If the difference in the pressure between EGR commanded ON versus commanded OFF is below a minimum threshold, then an EGR valve concern has occurred.

ENHANCED THERMOSTAT MONITOR

The enhanced thermostat monitor helps to reduce the time it takes to identify a thermostat concern. This monitor is executed once per drive cycle during a cold start and has a run duration of 300 seconds.

During a cold start, when the thermostat should be closed, the enhanced thermostat monitor uses intake air temperature, engine speed, and engine load to predict the engine coolant temperature. Once the predicted temperature has exceeded a target temperature for a length of time, the actual engine coolant temperature is compared to its required threshold. This threshold is 11°C (20°F) below the thermostat regulating temperature. If the engine coolant temperature exceeds this threshold, the thermostat is functioning correctly. If the engine coolant temperature is too low, the thermostat may be stuck open and a DTC may set.

EVAPORATIVE EMISSION (EVAP) LEAK CHECK MONITOR

The EVAP leak check monitor is an on board strategy designed to detect a leak in the EVAP system as small as 0.508 mm (0.020 inch). The EVAP leak check monitor is executed at ignition OFF if all conditions have been met on the previous drive cycle. The correct function of the individual components of the EVAP system, and the ability of the EVAP system to flow fuel vapor to the engine, are also monitored.

EVAP Leak Check Monitor

For plug in vehicles, the EVAP system is a sealed system by the use of the normally closed fuel tank isolation valve. If the natural vapor pressure or vacuum generation in the sealed fuel tank is sufficient the PCM will command the EVAP leak detection control module to check the fuel tank isolation valve, the EVAP purge valve, the switching valve in the EVAP leak detection control module and the lines between those components. The fuel tank pressure (FTP) sensor monitors the sealed portion of the EVAP system between the fuel tank isolation valve and the capless fuel filler pipe to determine the total pressure or vacuum in the fuel tank. If the target pressure or vacuum has been reached the fuel tank side of the fuel tank isolation valve is considered to have no leak. If the sealed portion of the EVAP system does not generate enough pressure or vacuum between the fuel tank isolation valve and the capless fuel filler pipe then the PCM will open the fuel tank isolation valve and will turn ON the EVAP leak detection control module vacuum pump to apply vacuum to the entire EVAP system.

For all others, the EVAP leak check monitor executes on the entire EVAP system to determine if a leak is present. The PCM will turn ON the EVAP leak detection control module switching valve and vacuum pump to apply a vacuum to the EVAP system for EVAP leak check monitoring.

The EVAP leak check monitor is initiated at ignition OFF if the conditions to run the monitor have been met during the preceding drive cycle. The EVAP leak check monitor is executed by using the individual components of the enhanced EVAP system as follows

1. For plug in vehicles, the FTP sensor is used to determine if the target pressure or vacuum necessary to carry out the leak check on the sealed fuel tank has been reached. For all others, the FTP sensor is used by the EVAP leak check monitor to determine if a leak is present in the fuel tank side of the vapor blocking valve.
2. For plug in vehicles, the fuel tank isolation valve blocks the flow of vapors from the fuel tank to the EVAP canister. The fuel tank isolation valve is normally closed to prevent the canister from becoming saturated in a situation where the engine does not run during a drive cycle, causing hydrocarbons (HC) to be released into the atmosphere. The fuel tank isolation valve will automatically open to relieve excess pressure or vacuum in the fuel tank if the fuel tank pressure or vacuum reaches a calibrated value. The PCM will open the fuel tank isolation valve only if the sealed section of the EVAP system does not generate enough pressure or vacuum to complete the EVAP leak check monitor or for refueling. For all others, the vapor blocking valve is normally open. The PCM will close the vapor blocking valve to determine if a leak exists in the fuel tank side of the vapor blocking valve or the EVAP canister side of the vapor blocking valve.
3. For plug in vehicles, the EVAP leak detection control module is used to seal the EVAP system from the atmosphere and draw a vacuum on the EVAP system for leak check monitoring. A vacuum pump inside the EVAP leak detection control module draws a vacuum on either the canister side of the fuel tank isolation valve or on the entire EVAP system as needed. If the initial target vacuum cannot be reached, a leak is detected and a DTC will set. The EVAP leak detection control module internal components are tested during the EVAP leak check monitor. A DTC will be set if a concern is detected with the internal EVAP leak detection control module components. For all others, the EVAP leak detection control module is used to seal the EVAP system from the atmosphere and draw a vacuum on the entire EVAP system for leak check monitoring. A vacuum pump inside the EVAP leak detection control module draws a vacuum on the EVAP system as needed. If the initial target vacuum cannot be reached, a leak is detected and a DTC will set. The EVAP leak detection control module internal components are tested during the EVAP leak check monitor. A DTC will be set if a concern is detected with the internal EVAP leak detection control module components.
4. The EVAP purge valve is used to control the purge flow from the EVAP canister during engine running conditions.
5. For plug in vehicles, the EVAP canister is used on the sealed EVAP system to collect fuel vapors during refueling only. For all others, the EVAP canister is used to collect fuel vapors during normal engine operations and refueling.
6. A valve inside the fuel vapor tube assembly prevents liquid fuel from entering the EVAP canister and the EVAP purge valve under any vehicle altitude, handling, or rollover condition.

FUEL SYSTEM MONITOR

The fuel system monitor is an on board strategy designed to monitor the fuel trim system. The fuel control system uses fuel trim tables stored in the PCM keep alive memory (KAM) to compensate for variability in fuel system components due to normal wear and aging. The fuel trim tables are based on engine RPM and engine load.

During closed loop fuel control, the fuel trim strategy learns the corrections needed to correct a biased rich or lean fuel system. The correction is stored in the fuel trim tables. The fuel trim has 2 means of adapting: long term fuel trim and short term fuel trim. Both are described in greater detail in this article under POWERTRAIN CONTROL SOFTWARE , Fuel Trim. Long term fuel trim relies on the fuel trim tables. Short term fuel trim refers to the desired air to fuel ratio parameter called LAMBSE. The LAMBSE is calculated by the PCM from the heated oxygen sensor (HO2S) inputs and helps maintain a 14.7:1 air to fuel ratio during closed loop operation.

Short term fuel trim and long term fuel trim work together. If the HO2S indicates the engine is running rich, the PCM corrects the rich condition by moving the short term fuel trim in the negative range (less fuel to correct for a rich combustion). If after a certain amount of time the short term fuel trim is still compensating for a rich condition, the PCM learns this and moves the long term fuel trim into the negative range to compensate and allow the short term fuel trim to return to a value near 0%. Input from the cylinder head temperature (CHT), intake air temperature (IAT), and mass airflow (MAF) sensors is required to activate the fuel trim system, which in turn activates the fuel system monitor.

As the fuel system components age or otherwise change over the life of the vehicle, the adaptive fuel strategy learns deviations from stoichiometry while running in the closed loop. These learned corrections are stored in the KAM as long term fuel trim (LONGFT1) corrections. As components continue to change beyond normal limits, or if a concern occurs, the LONGFT1 reaches a calibrated rich or lean limit and the adaptive fuel strategy is no longer allowed to compensate for additional fuel system changes. The LONGFT1 correction at their limits, in conjunction with a calibrated deviation in short term fuel trim (SHRTFT1), indicates a rich or lean fuel system concern. The fuel system monitor stores the appropriate DTC when a concern is detected as described below.

Scheme 48

1. The HO2S detects the presence of oxygen in the exhaust and provides the PCM with the feedback indicating air to fuel ratio.
2. A correction factor is added to the fuel injector pulse width calculation or MAF calculation, according to the long and short term fuel trims as needed to compensate for variations in the fuel system.
3. When deviation in the parameter LAMBSE increases, air to fuel control suffers and emissions increase. When LAMBSE exceeds a calibrated limit and the fuel trim table has clipped, the fuel system monitor sets a DTC as follows: P0171 - monitor detecting a lean shift in fuel system operation P0172 - monitor detecting a rich shift in fuel system operation
4. The malfunction indicator lamp (MIL) is activated after a concern is detected on two consecutive drive cycles. Typical fuel system monitor entry conditions: engine coolant temperature is between 68°C to 110°C (155°F to 230°F) engine load is greater than 30% intake air temperature is between -40°C to 65°C (-40°F to 150°F) fuel level is greater than 15% purge duty cycle of 0% Typical fuel monitor thresholds: lean condition: LONGFT1 is greater than 28% and SHRTFT1 is greater than 2% rich condition: LONGFT1 is less than 24% and SHRTFT1 is less than -2%

HEATED OXYGEN SENSOR (HO2S) MONITOR

The HO2S monitor is an on board strategy designed to monitor the HO2S for concerns or deterioration which can affect emissions. The HO2S monitor evaluates the HO2S for correct function. The HO2S senses the oxygen content in the exhaust flow. Input is required from the cylinder head temperature (CHT), intake air temperature (IAT), mass airflow (MAF) and crankshaft position (CKP) sensors to activate the HO2S monitor. The fuel system monitor and misfire detection monitor must also complete successfully before the HO2S monitor is enabled.

1. The rear HO2S is monitored for correct output voltage and is used for catalyst monitoring and fore aft oxygen sensor (FAOS) control. The typical HO2S outputs a voltage between 0 and 1.0 volt. The HO2S generates a voltage between 0 and 0.45 volt for a lean air fuel ratio. The HO2S generates a voltage between 0.45 and 1.1 volt for a rich air fuel ratio. The time between HO2S switches is monitored after vehicle startup and during closed loop fuel conditions. Excessive time between switches or no switches since startup indicates a concern. Since a lack of switching concern may be caused by HO2S concerns or by shifts in the fuel system, DTCs are stored that provide additional information for the lack of switching concerns. Different DTCs indicate whether the sensor always indicates lean, rich, or disconnected. The HO2S signal is also monitored for high voltage, in excess of 1.1 volts. An over voltage condition is caused by a HO2S heater or battery power short to the HO2S signal circuit. A functional test of the rear HO2S is done during normal vehicle operation. The peak rich and lean voltages are continuously monitored. Voltages that exceed the calibrated rich and lean thresholds indicate a functional sensor. If the voltages have not exceeded the thresholds after a long period of vehicle operation, the air to fuel ratio may be forced rich or lean in an attempt to get the rear sensor to switch. This situation normally occurs only with a green, less than 804.7 km (500 mi), catalyst. If the sensor does not exceed the rich and lean peak thresholds, a concern is indicated. Also, a rear HO2S response test is done during a deceleration fuel shut off (DFSO) event. Carrying out the HO2S response test during a DFSO event helps to isolate a sensor concern from a catalyst concern. The response test monitors how quickly the sensor switches from a rich to lean voltage. It also monitors if there is a delay in the response to the rich or lean condition. If the sensor responds very slowly to the rich to lean voltage switch or is never greater than a rich voltage threshold or less than a lean voltage threshold, a concern is indicated.
2. The front universal HO2S is checked for correct response rate. Response rate is the time it takes to switch from lean to rich or rich to lean. The amount of oxygen pumped in or out of the universal oxygen sensor detection cavity is monitored by the PCM. The amount of current required to pump oxygen in and out of the universal HO2S to maintain the universal HO2S at 0.45 volt is used by the PCM to calculate the air fuel ratio.
3. The malfunction indicator lamp (MIL) is activated after a concern is detected on two consecutive drive cycles.

Scheme 49

MISFIRE DETECTION MONITOR

The misfire detection monitor is an on board strategy designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, incorrect fuel metering, incorrect compression, or any other cause. The misfire detection monitor is enabled only when certain base engine conditions are first satisfied. Input from the cylinder head temperature (CHT), mass airflow (MAF), and crankshaft position (CKP) sensors is required to enable the monitor. The misfire detection monitor is also carried out during an on demand self-test.

Scheme 50

1. The powertrain control module (PCM) synchronized ignition spark is based on information received from the CKP sensor. The CKP signal generated is also the main input used in determining cylinder misfire.
2. The input signal generated by the CKP sensor is derived by sensing the passage of teeth from the crankshaft position wheel mounted on the end of the crankshaft.
3. The input signal to the PCM is then used to calculate the time between CKP edges and the crankshaft rotational velocity and acceleration. By comparing the accelerations of each cylinder event, the power loss of each cylinder is determined. When the power loss of a particular cylinder is sufficiently less than a calibrated value and other criteria are met, then the suspect cylinder is determined to have misfired.
4. The malfunction indicator lamp (MIL) is activated after one of the above tests fail on 2 consecutive drive cycles.

Low Data Rate System

The LDR misfire monitor uses a low data rate crankshaft position signal, one position reference signal at 10 degrees before top dead center (BTDC) for each cylinder event. The PCM calculates the crankshaft rotational velocity for each cylinder from this crankshaft position signal. The acceleration for each cylinder can then be calculated using successive velocity values. The changes in overall engine RPM are removed by subtracting the median engine acceleration over a complete engine cycle. The resulting deviant cylinder acceleration values are used in evaluating misfire in generic misfire processing.

Generic Misfire Processing

The acceleration that a piston undergoes during a normal firing event is directly related to the amount of torque that cylinder produces. The calculated piston acceleration values are compared to a misfire threshold that is continuously adjusted based on inferred engine torque. Deviant accelerations exceeding the threshold are conditionally labeled as misfires. The calculated deviant acceleration values are also evaluated for noise. Normally, misfire results in a non symmetrical loss of cylinder acceleration. Mechanical noise, such as rough roads or high RPM or light load conditions, produce symmetrical acceleration variations. A noise limit is calculated by applying a negative multiplier to the misfire threshold. If the noise limit is exceeded, a noisy signal condition is inferred and the misfire monitor is suspended for a brief interval. Noise free deviant acceleration exceeding a given threshold is labeled a misfire.

The number of misfires are counted over a continuous 200 revolution and 1, 000 revolution period. The revolution counters are not reset if the misfire monitor is temporarily disabled, such as for negative torque mode. At the end of the evaluation period, the total misfire rate and the misfire rate for each individual cylinder is computed. The misfire rate evaluated every 200 revolution period (Type A) and compared to a threshold value obtained from an engine speed and load table. This misfire threshold is designed to prevent damage to the catalyst due to sustained excessive temperature 871°C (1, 600°F). If the misfire threshold is exceeded and the catalyst temperature model calculates a catalyst mid-bed temperature that exceeds the catalyst damage threshold, the malfunction indicator lamp (MIL) blinks at a 1 Hz rate while the misfire is present. If the threshold is again exceeded on a subsequent driving cycle, the MIL is illuminated.

The misfire rate is evaluated every 1, 000 revolution period and compared to a single (Type B) threshold value to indicate an emission threshold, which can be either a single 1, 000 over-revolution event from startup or four subsequent 1, 000 over-revolution events on a drive cycle after start up. Diagnostic trouble code (DTC) P0316 is set if the Type B misfire threshold is exceeded during the first 1, 000 revolutions after engine startup. This DTC is stored in addition to the normal P03xx DTC that indicates the misfiring cylinder.

Profile Correction

The profile correction software learns the crankshaft tooth spacing under defueled engine conditions. The profile correction requires the engine to be shut down either at ignition OFF, or during normal vehicle operation, after the keep alive memory (KAM) reset. The learned corrections improve the high RPM capability of the monitor. The misfire monitor is not active until a profile is learned.

The profile correction software learns and corrects for mechanical inaccuracies in the crankshaft position wheel tooth spacing. Since the sum of all the angles between the crankshaft teeth must equal 360 degrees, a correction factor can be calculated for each misfire sample interval that makes all the angles between individual teeth equal. To prevent any fueling or combustion differences from affecting the correction factors, learning is done during engine shutdown. In order to minimize learning time for profile correction factors, the correction factors are learned after an engine shutdown is commanded and fuel is disabled while the generator motor spins the engine.

In order to protect the traction battery, to provide vehicle starting and to extend the shutdown, traction battery temperature and state of charge must be within operational limits. This condition occurs when either the ignition is turned to the OFF position (typically one ignition OFF induced engine shutdown), or the normal operating strategy shuts the engine down (typically multiple shutdown events during normal operation). During this shutdown, the generator motor spins the engine at approximately 1, 100 RPM, while delta time intervals are captured for computation of the correction factors. Average profile correction factors are calculated for each of the four combustion intervals over approximately 15 engine cycles. This procedure occurs once per KAM reset during the life of the vehicle. Since inaccuracies in the wheel tooth spacing can produce a false indication of misfire, the misfire monitor is not active until the corrections are learned. The software may be unable to learn a profile if the instantaneous profile calculations vary by more than a specified tolerance from the mean values. In this case DTC P0315 is set.

Typical profile correction learning entry conditions are, engine in fuel disabled mode for four engine cycles, engine speed between 800 and 1, 750 RPM, maximum RPM change during profile correction is 600 RPM, vehicle speed between 0 and 48 km/h (0 and 30 mph), the traction battery voltage above 216 volts, the traction battery temperature above -15°C (5°F), and the traction battery power discharge limit above 12 kW.

POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM MONITOR

The PCV system monitor consists of a modified PCV system design. The PCV valve is installed into the oil separator using a quarter turn camlock design to prevent accidental disconnection. High retention force molded plastic lines are used from the PCV valve to the intake manifold. The diameter of the lines and the intake manifold entry fitting are increased so that inadvertent disconnection of the lines after a vehicle is repaired either causes an immediate engine stall or does not allow the engine to be restarted. In the event the vehicle does not stall if the line between the intake manifold and PCV valve is inadvertently disconnected, the vehicle has a large vacuum leak that causes the vehicle to run lean at idle. This may illuminate the malfunction indicator lamp (MIL) after two consecutive driving cycles and may store a diagnostic trouble code (DTC).

For additional PCV information, refer to POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM .

TRANSMISSION CONTROL MODULE (TCM) COMPREHENSIVE COMPONENT MONITOR (CCM)

The TCM CCM detects concerns in the TCM system. The TCM CCM oversees internal and external TCM components, as well as internal and external circuits which provide input or output signals to the TCM.

When a monitored component concern is detected, the TCM stores a DTC and illuminates the powertrain malfunction indicator (wrench) lamp.

The following components are monitored

1. motor electronics cooling system (MECS)
2. auxiliary heater system (plug in vehicles only)
3. transmission oil pump (plug in vehicles only)
4. high voltage sensors
5. clean tach out
6. electric motor position sensors
7. electric motor current sensors
8. electric drive temperature sensors
9. electric vehicle mode

Motor Electronics Cooling System (MECS)

The MECS cools the TCM.

Auxiliary Heater System (Plug In Vehicles Only)

The auxiliary heater system provides cabin heat during electric vehicle mode for plug in vehicles.

Transmission Oil Pump (Plug In Vehicles Only)

The transmission oil pump provides transmission cooling and lubrication during electric vehicle mode for plug in vehicles.

High Voltage Sensors

The high voltage sensors monitor high voltage circuits at the inverters as well as the outputs to the generator and the traction motor.

Clean Tach Out

The clean tach out signal is received from the PCM. This signal is generated 10 degrees before top dead center for each cylinder. This signal is used to calculate the engine speed and crankshaft position.

Electric Motor Position Sensors

The electric motor position sensors are located on the electric motor and the generator. The electric motor position sensors measure the angular position of the rotors in both the motor and generator. These measurements are calculated to determine the motor and generator speed and acceleration.

The electric motor position sensors include the drive motor position sensor and the generator position sensor.

Electric Motor Current Sensors

The electric motor current sensors are located in the TCM. The electric motor current sensors measure the AC current for each phase of the motor and generator. These measurements are calculated to determine current magnitude and to verify correct connections between the AC voltage circuits and the electric motor and generator. The electric motor current sensors include the drive motor current sensor and the generator current sensor.

Electric Drive Temperature Sensors

The electric drive temperature sensors are located on the coil windings of the motor and generator. The electric drive temperature sensors include the drive motor coil temperature sensor, the generator coil temperature sensor, the transmission fluid temperature (TFT) sensor, the drive motor inverter temperature sensor and the generator inverter temperature sensor.

Electric Vehicle Mode

For plug in vehicles, the electric vehicle mode is a driver selectable switch the determines the operator request for one of three driving modes of operation. The three types of modes are

1. AUTO
2. EV Now
3. EV Later

The AUTO mode is normal operation of the system which minimizes the use of the gasoline engine until the battery charge is sufficiently depleted and requires recharging. The EV now mode disables the gasoline engine during most driving conditions when permitted by the high voltage traction battery. The EV later mode disables the electric-only drive system and prioritizes the gasoline engine to drive the vehicle to sustain the battery charge. The electric vehicle mode does not change with ignition key cycles. If the plug in energy is depleted or a system fault is detected, the vehicle system controller will switch to AUTO mode to maintain battery charge and continue operation.

VARIABLE CAMSHAFT TIMING (VCT) MONITOR

The VCT output driver in the PCM is checked electrically for opens and shorts. The VCT system is checked functionally by monitoring the closed loop camshaft position error correction. If the correct camshaft position cannot be maintained and the system has an advance or retard error greater than the calibrated threshold, a VCT control concern is indicated.

For additional information, refer to VARIABLE CAMSHAFT TIMING (VCT) SYSTEM .