Engine Controls - Description & Operation - (Hybrid): Other Ford Escape I facelift 2

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.

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Engine/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.

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ITEM DESCRIPTION CHART

VECI Acronym Definitions

ALVW: Adjusted Loaded Vehicle Weight, curb weight plus GVWR divided by 2.

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 Emissions

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.

LVW: Loaded Vehicle Weight, curb weight plus 300 pounds.

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 powertrain control module (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 (a total of six circuits and pins) between the PCM and the APP sensor assembly. The reference voltage circuits and the signal return circuits are shared with the reference voltage circuit and signal return circuit used by the electronic throttle body (ETB) throttle position (TP) sensor. 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 TORQUE-BASED ELECTRONIC THROTTLE CONTROL (ETC) .

Scheme 122

Air Conditioning (A/C) Clutch Relay

The A/C clutch relay (may be referred to as the wide open throttle (WOT) A/C cutoff relay) is wired normally open. There is no direct electrical connection between the A/C switch or electronic automatic temperature control (EATC) module and the A/C clutch. The PCM receives a signal indicating that A/C is requested. When A/C is requested, the PCM checks other A/C related inputs that are available. If these inputs indicate A/C operation is OK, and the engine conditions are OK (coolant temperature, engine RPM, throttle position), the PCM grounds the wide open throttle A/C cut-off (WAC) output, closing the relay contacts and sending voltage to the A/C clutch.

Air Conditioning Evaporator Temperature (ACET) Sensor

The ACET is connected to the dual automatic temperature control (DATC). Evaporator temperature is transmitted to the PCM from the DATC through the controller area network (CAN).

Air Conditioning (A/C) High Pressure Switch

The A/C high pressure switch is used for additional A/C system pressure control. For refrigerant containment control, the normally closed high pressure contacts open at a predetermined A/C pressure. This results in the A/C turning off, preventing the A/C pressure from rising to a level that would open the A/C high pressure relief valve.

For fan control, the normally open medium pressure contacts close at a predetermined A/C pressure. This grounds the ACPSW circuit input to the PCM. The PCM then turns on the high speed fan to help reduce the pressure.

For additional information, refer to the CLIMATE CONTROL .

Air Conditioning (A/C) Low Pressure Switch

The A/C low pressure switch is used for additional A/C system pressure control. This normally closed switch opens when the refrigerant pressure drops below 152 kPa (22 psi). This results in the A/C turning off, preventing the evaporator from freezing.

Air Conditioning Refrigerant Distribution Valve (ACRDV)

The ACRDV is a PCM-controlled solenoid that provides a regulated control of refrigerant flow to the passenger compartment loop. The PCM opens or closes the ACRDV based on the passenger compartment A/C request. The ACRDV is a normally closed valve, preventing the refrigerant flow. When the passenger compartment A/C is requested ON, the PCM provides a ground path to the solenoid which opens the ACRDV.

Scheme 123

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 speed control, the electronic throttle control (ETC), and the transaxle and regenerative braking systems. The BPP switch is hard wired to the PCM and supplies positive battery voltage (+12 volts) 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. The PID name for this switch is BOO1

Brake Pedal Switch (BPS)

The BPS used for vehicle speed control deactivation is a normally closed switch, which supplies positive battery voltage (+12 volts) to the PCM when the brake pedal is released. When the brake pedal is applied, the normally closed switch opens and power is removed from the BPS circuit to the PCM.

The normally closed BPS, 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. The PID name for this switch is BOO2

Camshaft Position (CMP) Sensor

The CMP sensor is a Hall-effect sensor that detects the position of the camshaft. The CMP 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 CMP signal to select the correct ignition coil to fire.

Scheme 124

Canister Vent (CV) Solenoid

During the evaporative emissions (EVAP) leak check monitor, the CV solenoid seals the EVAP canister from the atmospheric pressure. This allows the EVAP canister purge valve to obtain the target vacuum in the fuel tank during the EVAP leak check monitor.

Scheme 125

Clean Tachometer Output (CTO)

The PCM uses a crankshaft position (CKP) sensor input to calculate the engine speed. The engine speed information is then output to the TCM through the CTO circuit, as a frequency signal. The PCM also broadcasts a redundant engine speed message to the TCM over the controller area network (CAN) communication link. When the broadcasted engine speed disagrees with the hardwired CTO signal, or when the CTO circuit concern condition is detected, the TCM stores an appropriate diagnostic trouble code (DTC).

Coil On Plug (COP)

The COPs are part of the distributor less ignition system. They are the source of the high voltage which is used to generate the spark by the spark plug. The hybrid vehicle uses four COPs, one for each cylinder. The COPs are mounted directly onto 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 IGN START/RUN 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 126

Crankshaft Position (CKP) Sensor

The CKP sensor is a magnetic transducer mounted on the engine block adjacent to a pulse wheel located on the crankshaft. By monitoring the crankshaft mounted pulse wheel, the CKP is the primary sensor for ignition information to the PCM. The pulse wheel has a total of 35 teeth spaced 10 degrees apart with one empty space for a missing tooth. By monitoring the pulse wheel, the CKP sensor signal indicates the crankshaft position and speed information to the PCM. By monitoring the missing tooth, 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 determine if a misfire has occurred by measuring rapid decelerations between pulse wheel teeth.

Scheme 127

Cylinder Head Temperature (CHT) Sensor

The CHT sensor is a thermistor device in which the 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.

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.

The CHT sensor is installed in the aluminum cylinder head and measures the metal temperature. The CHT sensor provides complete engine temperature information and can be used to infer coolant temperature. If the CHT sensor conveys an overheating condition to the PCM, the PCM then initiates a fail-safe cooling strategy based on information from the CHT sensor. 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. 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 Fail-Safe Cooling Strategy.

Scheme 128

DC/DC Enable (DCE)

The DCE is an output from the PCM to the DC/DC converter. The PCM enables the DC/DC converter after the PCM receives a contractors closed message and no error messages. The DCE circuit is high (the low side driver is off) when the DC/DC is commanded on. When the DCE low side driver is activated, the DC/DC converter is commanded off. For additional information on DCE, refer to the DC/DC converter description in HYBRID ELECTRIC CONTROL HARDWARE .

DC/DC Fault

The DC/DC fault (DCF) signal is an input to the PCM from the DC/DC converter. This signal is low under normal conditions and switches high when a concern exists within the DC/DC converter cooling system, the high voltage power supply to the DC/DC converter, or the low voltage output system. The PCM disables or limits the operation of the DC/DC converter by the DC/DC enable circuit (DCE), when a DCF concern is indicated. For additional information on DCF, refer to the DC/DC converter description in HYBRID ELECTRIC CONTROL HARDWARE .

Electric Exhaust Recirculation Valve (EEGR) Valve

The EEGR valve is a water-cooled motor/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 builtin spring works to close the valve against the motor opening force.

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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 TORQUE-BASED ELECTRONIC THROTTLE CONTROL (ETC) .

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Evaporative Emission (EVAP) Canister Purge Valve

The EVAP canister purge valve is part of the enhanced EVAP system that is controlled by the PCM. This valve controls the flow of vapors (purging) from the EVAP canister to the intake manifold during various engine operating modes. The EVAP canister purge valve is a normally closed valve. The EVAP canister purge valve controls the flow of vapors electronically by way of a solenoid, eliminating the need for an electronic vacuum regulator and vacuum diaphragm. The PCM outputs a duty cycle between 0% and 100% to control the EVAP canister purge valve.

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ITEM DESCRIPTION CHART

Fan Control

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

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

PCM OUTPUT STATE FOR COOLING FAN SPEEDS

Fuel Injectors

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

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

The fuel injector is normally closed, and is operated by a 12-volt source from the fuel injector 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.

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ITEM DESCRIPTION CHART

Fuel Pump (FP) Module

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

Scheme 133

Fuel Tank Pressure (FTP) Sensor

The FTP sensor is used to measure the fuel tank pressure.

Scheme 134

Fuel Vapor Vent Valve

The fuel vapor vent valve is a PCM-controlled solenoid that isolates the fuel tank from the rest of the EVAP system. The fuel vapor vent valve is a normally open valve allowing the flow of vapors from the fuel tank to the electronic EVAP canister purge valve and the EVAP canister. The PCM controls the fuel vapor vent valve on/off cycle whenever it is desired to isolate the fuel tank from the rest of the EVAP system.

Scheme 135

Generator Shut Down (GSDN)

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

Heated Oxygen Sensor (HO2S)

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

Embedded with the sensing element is the HO2S heater. The heating element heats the sensor to a temperature of 800°C (1,472°F). At approximately 300°C (572°F) the engine can enter 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.

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Heater Pump

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

The pump is commanded on when the following conditions are met

1. The key is in the ON/START position.
2. The engine coolant temperature is above a minimum threshold 0°C (32°F) nominal.
3. The inferred ambient temperature is below a calibrated value 32°C (90°F) nominal.
4. The engine speed is below a calibrated threshold (nominal 4,000 RPM) including engine OFF.
5. The climate control mode switch is in any position other than OFF.

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

Scheme 137

Ignition Switch Position Run (ISP-R)

The ISP-R provides the PCM with a VBAT input signal from the ignition switch, indicating that the key is in either the ON or START position. When the operator turns the key to the OFF or ACC position, the internal combustion engine immediately ceases to provide power. The PCM coordinates the power down sequence by controlling the VPWR circuit and issuing the correct commands to shut down the electrical system in an orderly fashion. For additional information, refer to the Normal Power Down Sequence in HYBRID ELECTRIC CONTROL SOFTWARE . The PCM maintains power to the TCM through the VPWR until the power down sequence is complete. The TBCM is always powered directly from the low voltage battery which permits wake-up when the vehicle is off.

Ignition Switch Position Run/Start (ISP-RS)

The ISP-RS provides the PCM with a VBAT input signal from the ignition switch, indicating the key is in the START position.

Immediate Shut Down (ISDN) 1 and 2

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

Inertia Fuel Shut-off (IFS) Switch

The IFS switch consists of a steel cone held in place by a magnet. When a sharp impact occurs, the cone breaks loose from the magnet, rolls up a conical ramp and strikes a target plate which opens the electrical contacts of the switch. Once the switch is open, it must be manually reset before restarting the vehicle.

Refer to the Owner's Literature, Roadside Emergencies for the location of the IFS switch.

Scheme 138

Intake Air Temperature (IAT) Sensor

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

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

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

The IAT 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 139

Knock Sensor (KS)

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

Manifold Absolute Pressure (MAP) Sensor

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

The MAP sensor is part of the EGR system. The PCM uses information from the MAP, TP, MAF, CHT and CKP sensors to determine how much exhaust gas is introduced into the intake manifold.

Scheme 140

Mass Air Flow (MAF) Sensor

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

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

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

Scheme 141

Motor Electronics Coolant Temperature (MECT) Sensor

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

Scheme 142

Motor Electronics Cooling System (MECS) Pump

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

Scheme 143

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MOTOR ELECTRONICS COOLING SYSTEM COMPONENTS REFERENCE

Motor Shut Down (MSDN)

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

Throttle Actuator Control (TAC) Motor

The TAC motor is a DC motor controlled by the PCM (requires two wires). 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 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. For additional information, refer to the TORQUE-BASED ELECTRONIC THROTTLE CONTROL (ETC) .

TR Sensor and PCM Interface

The TR sensor is a linear potentiometer device that provides the PCM with a percentage of input voltage proportional to the rotational angle of the sensor shaft. The TR sensor consists of

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

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

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

Scheme 145

ITEM DESCRIPTION CHART

If the PCM detects a concern in one of TR signal inputs, it uses the other TR signal to determine what gear the driver selects. If the PCM detects one or more TR signals that are invalid, the PCM

1. allows the vehicle to travel in DRIVE position or LOW gear position if the vehicle was driving forward at a significant speed when the concern was detected.
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 indicator.

Universal Heated Oxygen Sensor (HO2S)

The universal HO2S, sometimes referred to as a wide band oxygen sensor, uses the typical HO2S combined with a current controller in the PCM to infer an air/fuel ratio relative to the stoichiometric air/fuel ratio. This is accomplished by balancing the amount of oxygen ions pumped in or out of a measurement chamber within the sensor. The typical HO2S within the universal HO2S is used to detect the oxygen content of the exhaust gas in the measurement chamber. The oxygen content inside the measurement chamber is maintained at the stoichiometric air/fuel ratio by pumping oxygen 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/fuel ratio in the measurement chamber varies in proportion to the air/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/fuel ratio. The measured air/fuel ratio is actually the output from the current controller in the PCM and not a signal that comes directly from the sensor.

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

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

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

Modifications to OBD Vehicles

Modifications or additions to the vehicle may cause incorrect operation of the OBD system. Non-factory anti-theft 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.

DC/DC Converter

The purpose of the DC/DC converter is to function as an alternator in a conventional powertrain. The powertrain control module (PCM) controls operation of the DC/DC converter. Because the converter does not use any moving parts, the low voltage battery is charged when the vehicle drives with the engine ON or OFF. This is accomplished by converting power from the high voltage traction battery to a regulated output voltage of a nominal 14.5 volts, while supplying a load current of up to 110 amps. The PCM controls the DC/DC enable (DCE) hardwired signal to switch the DC/DC converter on and off. The DC/DC converter provides feedback to the PCM using the hardwired DC/DC fault (DCF) signal. The DCF signal indicates to the PCM when the converter is non-operational or when the concern occurred. The DC/DC converter is cooled by the motor electronics cooling system and is located on the passenger side in the engine compartment.

Scheme 146

Hybrid Electric Indicators

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

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

Over-Temperature Indicator

The PCM monitors the engine, the motor electronics coolant temperature (MECT), and the electronically controlled continuously variable transaxle (CVT) for an over-temperature condition. If either of the temperatures exceed their threshold value, the fail-safe cooling status changes status to ON, and the PCM broadcasts an over-temperature indicator on controller area network (CAN) message to the instrument cluster. The instrument cluster then illuminates the indicator light. The over-temperature indicator is extinguished when the temperature returns below the threshold value.

Scheme 147

Powertrain Malfunction Indicator (Wrench)

The powertrain malfunction indicator (wrench) is illuminated whenever 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 diagnostic trouble code (DTC) and broadcasts a caution on CAN message to the instrument cluster. Upon receiving the CAN message, the instrument cluster turns the indicator on.

Two actions can extinguish the powertrain malfunction indicator (wrench)

1. the module requesting the indicator on is reset.
2. the concern is not present anymore and the key 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 instrument cluster prove-out when the key is cycled from the OFF to the ON position.

Scheme 148

ITEM DESCRIPTION CHART

Hazard Indicator (Red Triangle)

The hazard indicator is illuminated whenever 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 hazard on CAN message to the instrument cluster. Upon receiving the CAN message, the instrument cluster turns the indicator on.

Two actions can extinguish the hazard indicator

1. the module requesting the indicator on is reset.
2. the concern is not present anymore and the key is cycled.

If the hazard indicator flashes at the once per second rate, it indicates that the vehicle is in the engine cranking diagnostic mode. Refer to DIAGNOSTIC MODES for engine cranking diagnostic mode. The hazard indicator illuminates for 3 seconds during the instrument prove-out when the key is cycled from the OFF to the ON position.

Scheme 149

High Voltage Cables

The high voltage cables connect the high voltage traction battery with the electronically controlled CVT, and the electronically controlled CVT with the DC/DC converter. The harness is orange and contains high voltage positive and high voltage negative wires. Each of the high voltage wires contains a corresponding high voltage interlock (HVIL) circuit.

High Voltage Interlock (HVIL) Circuit

The HVIL circuit, used in conjunction with the front and rear inertia fuel shutoff (IFS) switches, disables the vehicle if a collision occurs or an open circuit concern in the high voltage connection is detected. The HVIL circuit is internal to the high voltage harness, which connects the traction battery, the electronically controlled CVT, and the DC/DC converter. The transaxle control module (TCM) and the traction battery control module (TBCM) monitor the HVIL circuit for a low battery voltage. Whenever that voltage drops below a calibrated threshold, the high voltage traction battery immediately opens its high voltage contractors, the electronically controlled CVT discharges the high voltage capacitors, and the TCM stores the DTC P0A0A. This action is initiated when the vehicle is disabled and cannot be driven.

Scheme 150

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. For information on the DC/DC converter, refer to HYBRID ELECTRIC CONTROL HARDWARE , DC/DC converter. The low voltage battery functions are

1. the voltage stabilizer in the system
2. the power source for the power distribution box
3. the power source for all control modules
4. the power source for the traction battery during the jump start procedure

Traction Battery Control Module (TBCM)

Refer to the HIGH VOLTAGE TRACTION BATTERY for more information on TBCM and diagnostics.

Transaxle Control Module (TCM)

Note. The TCM is a part of the electronically controlled CVT assembly and cannot be repaired as a separate component. Refer to AUTOMATIC TRANSAXLE/TRANSMISSION EXTERNAL CONTROLS for electronically controlled CVT repair procedures.

The microprocessor that controls operation of the electronically controlled CVT is called the TCM. The TCM receives a variety of 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. To retrieve DTCs from the TCM, carry out an on-demand and continuous memory self-test.

Transaxle Control Module (TCM) Keep Alive Memory (KAM)

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

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 .

Integrated Electronic Ignition (EI) System

The EI system consists of a crankshaft position (CKP) sensor, ignition coils, connecting wiring, and PCM. The coil on plug (COP) integrated EI system uses a separate coil for each spark plug and each coil is mounted directly onto the plug. The COP integrated EI system eliminates the need for spark plug wires, but requires input from the camshaft position (CMP) sensor.

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 190-pin PCM which has 3 separate electrical harness connectors.

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

The PCM stores information in keep alive RAM (a memory integrated circuit chip) about vehicle operating conditions, and then uses this information to compensate for component variability. KAM remains powered when the key is off so that this information is not lost.

Powertrain Control Module (PCM) Power and Ground Signals

Vehicle Buffered Power (VBPWR)

The VBPWR is a PCM-supplied power 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)

VPWR is the primary source of PCM power. 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.

Mass Air Flow Return (MAF RTN)

The MAF RTN is a dedicated analog signal return from the mass air flow (MAF) sensor. It serves as a ground offset for the analog voltage differential input by the MAF sensor to the PCM.

Signal Return (SIG RTN)

The SIG RTN is a dedicated ground circuit used by most EEC sensors and some other inputs.

Power Ground (PWR GND)

The PWR GND is an electric current path return for VPWR voltage circuit. The purpose of the PWR GND is to maintain sufficient voltage at the PCM.

Gold Plated Pins

Some engine control hardware has gold plated pins on the connectors and mating harness connectors to improve electrical stability for low current draw circuits and to enhance corrosion resistance. Replace damaged gold terminals with new gold terminals.

Creep Mode

The hybrid electric system delivers torque to the wheels to mimic the creep normally found on vehicles equipped with an automatic transmission. The powertrain control module (PCM) commands a predetermined amount of torque to be delivered to the output shafts of the electronically controlled continuously variable transaxle (CVT). This torque is delivered from a combination of sources: 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 slightly vary if ambient temperature, altitude, relative humidity, engine temperature, or weight of the vehicle changes.

Driving Modes

There are 5 fundamental operating modes in the hybrid electric system

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

Electric Mode

The hybrid electric system operates in the electric 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, the generator motor, or a combination of both. This is a preferred mode whenever the desired torque is low and the electrical system, rather than the engine, can produce it more efficiently. The electric mode is also used in reverse because the engine can deliver torque only in a forward direction.

Scheme 151

Positive Split Mode

In this mode the internal combustion 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 power and desired power at the wheels. This mode is preferred whenever the traction battery needs to be charged.

Scheme 152

Negative Split Mode

In this mode the internal combustion engine is running but the generator motor is reducing the engine speed. This mode is never preferred but occurs when all of the following vehicle conditions are met

1. The engine is running.
2. The vehicle speed is high.
3. The high voltage traction battery is charged.
4. Reducing engine throttle is not desired.

Scheme 153

Neutral Gear Mode

The hybrid electric system operates in this mode when the driver selects NEUTRAL. In neutral gear the electronically controlled CVT does not deliver any positive or negative torque to the output shafts of the vehicle. The neutral gear actually consists of 2 neutral operating states: active neutral activated above 10 km/h (6 mph), and passive neutral activated below 10 km/h (6 mph). In active neutral, the generator motor is permitted to start and stop the internal combustion engine as needed to maintain the high voltage traction battery charge, and provide A/C. In passive neutral, the engine must remain in the state it was (running or not running) when the mode was entered and is not permitted to change state (start or stop). If the engine is running when entering passive neutral, the speed control of the engine is transferred from the generator motor to the engine itself. The engine controlling its own speed in passive neutral is described as secondary idle. The vehicle cannot be started in passive neutral, but can be started in active neutral.

Engine Cranking Mode

The electronically controlled CVT 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 1,000 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 times.

Scheme 154

Limited Operating Strategy (LOS) Modes

For some hybrid electric system concerns the PCM may initiate one or more of the LOS modes. The objective of the LOS modes is to manage vehicle operation after one or more of the following systems are disabled due to a concern: engine, electronically controlled CVT, traction battery, or 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.

When the PCM detects system faults for which the LOS mode is initiated, it stores a corresponding diagnostic trouble code (DTC). The root cause of the concern that initiated the LOS mode may be in a different subsystem or component than indicated by the DTC. Therefore, these DTCs should be considered LOS or failure mode effects management (FMEM) only and are always assisted by the other, more detailed, circuit DTCs. The circuit DTCs should always be used to diagnose the problem before LOS or FMEM DTCs. LOS or FMEM DTCs do not mean the subsystem or component they describe actually failed, but indicate the subsystem or component that is effected by the LOS mode.

1. P1A0C Hybrid Powertrain Control Module - Engine Disabled
2. P1A0D Hybrid Powertrain Control Module - Generator Disabled
3. P1A0E Hybrid Powertrain Control Module - Motor Disabled
4. P1A0F Hybrid Powertrain Control Module - Vehicle Disabled
5. P1A10 Hybrid Powertrain Control Module - Battery Disabled
6. P1A13 Hybrid Powertrain Control Module - Regenerative Braking Disabled
7. P1A14 Hybrid Powertrain Control Module - Transmission Disabled

Normal Power Down Sequence

The PCM must conduct a normal power-down sequence. Whenever the key is turned to the OFF or ACC position, modules powered up by the RUN circuit immediately shut down. However the PCM, transaxle control module (TCM), and the traction battery control module (TBCM) stay on, until the power down sequence is complete. The PCM keeps the TCM alive by controlling the PCM relay which provides power to the TCM. The TBCM is powered directly from the low voltage battery which permits wake-up function when the vehicle is off. During the power down sequence the PCM

1. cuts the power to injectors and ignition coils (engine shut down).
2. requests the TCM to disable high voltage inverters.
3. disables the DC/DC converter.
4. requests the TBCM to open the high voltage contractors.
5. requests the TCM to discharge the high voltage inverter capacitors.
6. opens the PCM 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 TBCM storing DTCs.

Power Up Sequence

The PCM conducts a power up sequence every time the key is turned from the OFF to the START position. The power up sequence is carried out only with the electronically controlled CVT gear selector in the PARK position. During the power up sequence the PCM

1. initializes and begins CAN communications with the TCM and the TBCM.
2. checks for TCM error status.
3. requests the TBCM to close the high voltage contractors.
4. enables the DC/DC converter.
5. starts the internal combustion engine.

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

Regenerative Braking

The regenerative braking is a software strategy and is controlled by the PCM, the TCM, and the TBCM. 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 PCM 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 PCM strategy smoothly blends regenerative and friction brake effort to make the dual brake operation transparent to the driver.

Scheme 155

Vehicle System Controller (VSC)

The PCM, TCM and traction battery control module TBCM are connected to a high-speed CAN to exchange information messages. The VSC is a software function integrated inside the PCM, and is responsible for vehicle system operation, generating and sending commands to initiate appropriate actions such as LOS modes when serious concern is detected. The PCM also stores DTCs along with the freeze frame PID related to the LOS action that was initiated. To retrieve DTCs from the PCM an on-demand and continuous memory self-test must be carried out.

Computer Controlled Shutdown

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

The PCM controls the PCM power relay when the key is turned to the ON or START position, by grounding the PCM relay control (PCMRC) circuit. After the key is turned to the OFF, ACC or LOCK position, the PCM stays powered up until the correct engine shutdown occurs.

The ignition switch position run (ISP-R) and the injector power monitor (INJPWRM) circuits provide the key state input to the PCM. Based on the ISP-R and INJPWRM signals the PCM determines when to power down the PCM power relay.

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 activated by the PCM only in the event that 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 may 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 period of time when an overheat condition exists.

The engine temperature is controlled by varying and alternating the number of disabled fuel injectors. This allows all cylinders to cool. When the fuel injectors are disabled, their respective cylinders work as air pumps, and this air is used to cool the cylinders.

On the hybrid vehicle, the PCM provides a fail-safe cooling status information to the instrument cluster through the controller area network (CAN). The PCM sends a CAN message signal to the cluster indicating what fail-safe cooling mode the vehicle is in. There are three levels of this message, which are: normal operating mode, fail-safe mode one, and fail-safe mode 2. The cluster turns the red temperature indicator off if normal operating mode is received, turns the red temperature indicator on if it receives a fail-safe mode 1 message, and it flashes the red temperature indicator if it receives a fail-safe mode 2 message. During fail-safe mode 1 the PCM sets DTC P1285 and during fail-safe mode 2 the PCM sets DTC P1299.

Note. The instrument cluster red temperature indicator is also used by the motor electronics cooling system loop and may be illuminated by an over temperature condition in that subsystem. The motor electronics cooling system loop includes the generator, DC/DC converter, and the traction motor. The motor electronics cooling system loop also contains a motor electronics coolant temperature (MECT) sensor and motor electronics cooling system (MECS) pump to circulate the coolant. For additional information on the MECT sensor and the MECS pump, refer to ENGINE CONTROL COMPONENTS .

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/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/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 stoichiometric. The desired air/fuel control parameter is called short term fuel trim (SHRTFT1) where stoichiometric 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 stoichiometric. 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/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/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/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 (signals) between electronic modules or nodes. Two or more signals can be sent over one CAN circuit allowing two or more electronic modules or nodes 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 high (+) and CAN low (-) lines to the data link connector (DLC). The diagnostic data such as self-test DTCs or 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.

FAILURE TYPE BYTE REFERENCE

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.

STATUS BYTE REFERENCE

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 controller area network (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 MODULE COMMUNICATIONS NETWORK .

Malfunction Indicator Lamp (MIL)

The MIL alerts the driver that the powertrain control module (PCM) has detected an on board diagnostic (OBD) emission-related component or system concern. When this occurs, an OBD diagnostic trouble code (DTC) is set.

1. The MIL is located on the instrument cluster and is labeled as International Standards Organization (ISO) engine symbol.
2. Power is supplied to the MIL whenever the key is in the ON or START position.
3. The MIL remains on in the on/start mode as a bulb check during the instrument cluster prove-out for approximately 4 seconds.
4. If the MIL remains on after the bulb check: the PCM illuminates the MIL for an emission related concern and a DTC is set. the instrument cluster illuminates the MIL if the PCM does not send a control message to the instrument cluster. the PCM is operating in the hardware limited operation strategy (HLOS).
5. If the MIL remains off during the bulb check, there is: an instrument cluster concern. an instrument cluster wiring concern.
6. To turn off the MIL after a repair, a reset command from the scan tool must be sent, or three consecutive drive cycles must be completed without a concern.
7. For any MIL concern, refer to «QT1»(ref-342304-S15846582622009092300000) .
8. If the MIL blinks at a steady rate, a severe misfire condition may exist.
9. The MIL flashes after a period of time with the key in the RUN position (engine not running) if DTC P1000 is set.

Scheme 156

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 575°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 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.

The hybrid vehicle is a PZEV and has two separate HO2S in the exhaust stream. The front sensor is near the exhaust manifold (stream 1), and the rear sensor (stream 2) is mounted after the light-off catalyst.

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 EXHAUST SYSTEM .

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.

Heated Oxygen Sensors (HO2S)

The HO2S provide 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.

Enhanced Evaporative Emission (EVAP) System

The enhanced EVAP system consists of a canister vent (CV) solenoid, EVAP canister, EVAP canister purge valve, fuel tank, capless fuel tank filler pipe, fuel vapor control valve, fuel vapor vent valve, fuel tank pressure (FTP) sensor, intake manifold hose assembly, powertrain control module (PCM), the connecting wires, and fuel vapor hoses.

1. The enhanced EVAP system uses inputs from the cylinder head temperature (CHT) sensor, the intake air temperature (IAT) sensor, the mass air flow (MAF) sensor, the vehicle speed and the fuel tank pressure (FTP) sensor to provide information about engine operating conditions to the PCM. The fuel level input (FLI) and FTP sensor signals to the PCM are used by the PCM to determine activation of the EVAP leak check monitor based on the presence of vapor generation or fuel sloshing.
2. The PCM determines the desired amount of purge vapor flow to the intake manifold for a given engine condition. The PCM then outputs the required signal to the EVAP canister purge valve. The PCM uses the enhanced EVAP system inputs to evacuate the system using the EVAP canister purge valve, seals the enhanced EVAP system from the atmosphere using the CV solenoid, and uses the FTP sensor to measure the total vacuum lost for a period of time.
3. The CV solenoid seals the enhanced EVAP system from the atmosphere during the EVAP leak check monitor.
4. The PCM outputs a duty cycle between 0% and 100% to control the EVAP canister purge valve.
5. The FTP sensor monitors the fuel tank pressure during engine operation and continuously transmits an input signal to the PCM. During the EVAP monitor testing, the FTP sensor monitors the fuel tank pressure or vacuum bleed-up.
6. A valve inside the fuel tank-mounted fuel vapor tube assembly prevents liquid fuel from entering the EVAP canister and the EVAP canister purge valve under any vehicle altitude, handling, or rollover condition.
7. The fuel vapor vent valve isolates the fuel tank from the rest of the EVAP system when the vapor flow is required only from the EVAP canister, and not from the fuel tank.

The enhanced EVAP system, including all the fuel vapor hoses, can be checked when a leak is detected by the PCM.

Scheme 157

Hardware

The EEGR valve is a water-cooled motor/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 builtin spring works to close the valve against the motor opening force.

Scheme 158

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. The front inertia fuel shut-off (IFS) switch is used to disable the voltage to the fuel pump control module in the event of a collision. The front IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision.
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 and Fuel Pump Monitor.
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-342307-S10235106352009092300000) .
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 159

Fuel Pump Control - Dual Speed MRFS

The FP signal is a duty cycle command sent from the PCM to the fuel pump control module. The fuel pump control module uses the FP 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 15-47%. 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 key 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 DRIVER MODULE DUTY CYCLE SIGNALS

Fuel Filters

The system contains three filtering or screening devices. Refer to FUEL TANK & LINES 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 module that allows clean fuel to return to the fuel tank.

Internal Combustion Engine

The 2.5 liter variable compression engine uses the Atkinson cycle for its operation. Sometimes referred to as the five-stroke cycle, it uses a normal intake stroke but at the start of the compression stroke, the intake valve stays open. This allows a back flow stroke of air from the cylinder into the intake manifold which decreases manifold vacuum that requires energy to overcome. Although the intake valve stays open in the compression stroke, it closes early enough to produce sufficient cylinder pressure for combustion. The Atkinson cycle engine is designed to operate in a smaller RPM band than a conventional engine, and it runs mainly at the most efficient RPM range for the maximum fuel economy. The Atkinson cycle is up to 10% more efficient than a conventional 4-stroke gasoline engine, but it has reduced low engine RPM torque. The engine is mechanically linked to the electronically controlled CVT by the crankshaft and transaxle input shaft. The engine primarily provides torque to the output shafts, charges the high voltage traction battery using the generator motor, and runs the A/C compressor when requested. It also produces heat for the passenger compartment climate control.

Electronically Controlled Continuously Variable Transaxle (CVT)

The primary objective of the electronically controlled CVT is to deliver torque to the drive axles of the vehicle. The CVT transmits input torque from the internal combustion engine, or uses electrical power from the high voltage traction battery. The electrical power is converted into mechanical power by the traction motor and the generator motor. The electronically controlled CVT operates in several different modes, and under certain conditions can transmit power from the traction motor and engine simultaneously or independently. For additional information, refer to HYBRID ELECTRIC CONTROL SOFTWARE , operating modes.

The key electronically controlled CVT components are

1. planetary gear set
2. generator motor
3. traction motor
4. transaxle control module (TCM)

Note. Do not attempt to make repairs to any components within the transaxle. Refer to AUTOMATIC TRANSAXLE/TRANSMISSION EXTERNAL CONTROLS for repair procedures.

Planetary Gear Set

The planetary gear set, the generator motor, and the traction motor are internal to the electronically controlled CVT. The planetary gear set mechanically links the internal combustion engine, the electric traction motor, and the electric generator together. It distributes power between the three elements that it connects. 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.

Scheme 160

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 (internal to the transaxle) 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 and the generator control unit (GCU). Depending on the mode of operation, the generator motor can rotate in the same (clockwise) or reverse (counter clockwise) direction as the internal combustion engine. The TCM also monitors generator position, speed, phase current, power inverter temperature, coil temperature, and voltage. It processes a variety of PCM and traction battery control module (TBCM) inputs to determine generator function. The inputs are divided into two categories: the hardwired signals and the network messages. The inputs used to determine generator function include the total torque desired, the engine speed desired, the generator mode, the generator shutdown, and the vehicle mode. The generator operates in one of the following generator modes: torque, speed, engine cold start, engine normal start, engine high speed start, and engine enhanced speed control stop. The generator is used as a starter for the internal combustion engine, charges high voltage traction battery, and controls engine speed. The TCM reports the generator error status to the PCM. The PCM initiates an appropriate limited operating strategy (LOS) mode and sets the diagnostic trouble code (DTC) P1A0D (Hybrid powertrain control module - generator disabled) based on the error status it received. The TCM also sets a DTC which indicates the cause of the generator motor concern.

Scheme 161

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 (internal to the transaxle) 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 and the motor control unit (MCU). The traction motor can deliver positive torque by propelling the vehicle in the forward or reverse direction. It can also provide negative torque by functioning as a generator during the regenerative braking. The TCM receives input from the position sensor as well as the motor coil temperature sensor. The TCM monitors the motor coil temperature and sets a DTC if the temperature exceeds a maximum threshold value. The TCM also monitors motor position, speed, phase current, power inverter temperature, and voltage. The TCM processes a variety of the inputs from the PCM and the traction battery control module (TBCM) to determine motor function. The inputs are divided into two categories: the hardwired signals and the network messages. The inputs used to determine motor function include the total torque desired, the motor inverter shutdown, and the vehicle mode. The traction motor is used to provide torque to the axle shafts and recharge the high voltage traction battery during the regenerative braking. The TCM reports the motor error status to the PCM. The PCM initiates an appropriate LOS mode and sets the DTC P1A0E (Hybrid powertrain control module - traction motor disabled) based on the error status received. The TCM also sets a DTC which indicates the cause of the traction motor concern.

Scheme 162

High Voltage Traction Battery

The high voltage traction battery stores energy for later use by the traction motor and the generator motor. It is connected to both the traction motor and the generator motor by the high voltage cables. The traction motor uses the traction battery power when it propels the vehicle. The generator motor uses the traction battery power when it starts the internal combustion engine. The traction battery also provides energy to the DC/DC converter, which steps down the high voltage to maintain the low voltage system charge. For more information on the charging system, refer to HYBRID ELECTRIC CONTROL HARDWARE , DC/DC converter. Refer to CHARGING SYSTEM for more information on the high voltage traction battery and diagnostics.

The EI system consists of a crankshaft position (CKP) sensor, coil(s) on plug (COP), and the PCM. The COP integrated EI system uses a separate coil per spark plug, and each coil is mounted directly onto the plug. The COP integrated EI system requires input from the camshaft position (CMP) sensor. Operation of the components are as follows

1. NOTE: Electronic ignition engine timing is entirely controlled by the PCM. Electronic ignition engine timing is NOT adjustable. Do not attempt to check base timing. You will receive false readings. The CKP sensor is used to indicate crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted to the crankshaft. The CMP sensor is used by the COP integrated EI system to identify the top dead center (TDC) of compression of cylinder 1 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 it to the communication network. The PCM also sends it to the transaxle control module (TCM) as a hardwired clean tachometer output (CTO) signal.

Scheme 163

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 (CMP) 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 (requires two wires).
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 first TP signal (TP1) has a negative slope (increasing angle, decreasing voltage) and the second signal (TP2) 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 (IPC) 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)

ELECTRONIC THROTTLE MONITOR OPERATION

Accelerator Pedal Position (APP) and Throttle Position (TP) Sensor Inputs

ACCELERATOR PEDAL POSITION (APP) SENSOR CHECK

Monitor execution is continuous. Monitor false detection duration is less than 1 second to register a concern. Refer to DTC CHART for additional DTC information.

THROTTLE POSITION (TP) SENSOR CHECK

Electronic Throttle Actuator Control (TAC) Output

ELECTRONIC TAC OPERATION CHECK

Variable Camshaft Timing (VCT) System

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

1. The PCM receives input signals from the intake air temperature (IAT), cylinder head temperature (CHT), CMP, accelerator pedal position (APP) sensor (via requested torque), mass air flow (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 oil temperature and engine speed inputs. During cold start emissions reduction mode, the camshaft position is determined via engine speed and estimates of engine coolant temperature and catalyst temperature (estimated from other sensors already used such as IAT/CHT/MAF/CKP). During part and wide open throttle, the camshaft position is determined by engine RPM, load and accelerator pedal position. The VCT system does not operate until the engine is at normal operating oil 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 CMP positioning.
4. The VCT 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/flow advances or retards the cam 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.
5. When the VCT 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 two 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.

Scheme 164

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 powertrain control module (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.

The catalyst efficiency monitor calculates the rear HO2S signal lengths for 10-20 seconds during part-throttle, closed-loop fuel conditions after the engine is warmed-up, the inferred catalyst temperature is within limits, and fuel tank vapor purge is disabled. The catalyst monitor is enabled for 10-20 seconds per drive cycle. When the catalyst monitor is active, the PCM commands a fixed fuel control routine. During monitor operation the rear HO2S signal lengths are continually calculated. To determine the index ratio, the calculated rear HO2S signal length is then divided by a calibrated signal length, which has compensation for mass air flow. The calibrated signal length is based on the signal length of an HO2S placed after a catalyst without a wash coat. An index ratio near 0.0 indicates high oxygen storage capacity, hence high HC efficiency. An index ratio near 1.0 indicates low oxygen storage capacity, hence low HC efficiency. If the actual index ratio exceeds the threshold index ratio, the catalyst is considered failed.

Catalyst Monitor Execution

Catalyst monitor execution is once per drive cycle. Typical monitor duration is 10-20 seconds. In order for the catalyst monitor to run, the HO2S monitor must be complete and the EVAP system functional with no stored DTCs. If the catalyst monitor does not complete during a particular drive cycle, the already accumulated switch/signal data is retained in the KAM and is used during the next drive cycle to allow the catalyst monitor a better opportunity to complete.

Scheme 165

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 model. The expected catalyst temperature model 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 properly. This ratio correlates to tailpipe emissions, and a malfunction indicator lamp (MIL) illuminates 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. Engine coolant temperature at the start of the monitor is between 1.67°C (35°F) and 37.78°C (100°F)
2. Barometric pressure is above 74.5 kPa (22 in-Hg)
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%

Comprehensive Component Monitor (CCM)

The CCM monitors for 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) canister 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 air flow (MAF) sensor, intake air temperature (IAT) sensor, cylinder head temperature (CHT) sensor, crankshaft position (CKP) sensor, camshaft position (CMP) sensor, air conditioning pressure switch (ACPSW).
2. Outputs: A/C cutout (A/CCR), EVAP canister purge valve, canister vent (CV) solenoid, variable camshaft timing (VCT) 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 166

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 exhaust gas recirculation (EGR) system. The monitor is activated during EGR system operation and after certain base engine conditions are satisfied. Input from the cylinder head temperature (CHT), intake air temperature (IAT), throttle position (TP), mass air flow (MAF), and manifold absolute pressure (MAP) sensors is required to activate the EGR system monitor. Once activated, the EGR system monitor carries out each of the tests described below during the engine modes and conditions indicated. Some of the EGR system monitor tests are also carried out during the on-demand self-test.

The EEGR system monitor consists of an electrical and functional test that checks the stepper motor and the EGR system for correct flow. The powertrain control module (PCM) controls the EGR valve by commanding from 0 to 52 discreet increments or steps to get the valve from fully closed to fully open. 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 power, or short to ground has occurred in one or more of the stepper motor coils/circuits for a calibrated period of time. If a concern has been detected, the EGR system is disabled, setting the key on engine running (KOER), and continuous diagnostic trouble code (DTC) P0403. Additional monitoring is suspended for the remainder of the driving cycle, or until the next engine startup.

After the engine has warmed up and normal EGR rates are being commanded by the PCM, the EGR flow check is carried out. The flow test is carried out once per drive cycle when a minimum amount of EGR is requested and the remaining entry conditions required to initiate the test are satisfied. If a concern is detected, the EGR system and the EGR system monitor are disabled until the next engine startup.

The EGR flow test is done by observing the behavior of two different values of MAP - the analog MAP sensor reading, and the inferred MAP (MAP calculated from the MAF sensor, TP, and RPM). During normal, steady-state operating conditions, the EGR is intrusively commanded ON to a specified percentage. Then, the EGR is commanded OFF. If the EGR system is working correctly, there is a significant difference in both the observed and the calculated values of MAP between the EGR ON and the EGR OFF states.

When the flow test entry conditions have been satisfied, the EGR is commanded to flow at a calibrated test rate (about 10%). At this time, the value of MAP is recorded (EGR ON MAP). The value of inferred MAP EGR ON IMAP is also recorded. Next, the EGR is commanded off (0%). Again, the value of MAP is recorded (EGR OFF MAP). The value of EGR OFF IMAP is also recorded. Typically, 7 such ON/OFF samples are taken. After all the samples have been taken, the average EGR ON MAP, EGR ON IMAP, EGR OFF MAP and EGR OFF IMAP values are stored.

Next, the differences between the EGR ON and EGR OFF values are calculated

1. MAP delta equals EGR ON MAP - EGR OFF MAP (analog MAP).
2. IMAP delta equals EGR ON IMAP - EGR OFF IMAP (inferred MAP).

If the sum of MAP delta and IMAP delta exceeds a maximum threshold or falls below a minimum threshold, DTC P0400 (high or low flow concern) is registered.

As an additional check, if the EGR ON MAP exceeds a maximum threshold (BARO, a calibrated value), DTC P0400 low flow concern is registered.

BARO is inferred at engine startup using the key on engine off (KOEO) MAP sensor reading. It is updated during high, part-throttle or high RPM engine operation.

If the inferred ambient temperature is less than -7°C (20°F), greater than 54°C (130°F), or the altitude is greater than 8,000 feet (BARO less than 22.5 in Hg), the EGR flow test cannot be reliably done. In these conditions, the EGR flow test is suspended and a timer starts to accumulate the time in these conditions. If the vehicle leaves these extreme conditions, the timer starts to decrement, and if conditions permit, attempts to complete the EGR flow monitor. If the timer reaches 500 seconds, the EGR flow test is disabled for the remainder of the current driving cycle and the EGR monitor I/M readiness bit is set to a ready condition.

A DTC P1408, like P0400, indicates an EGR flow concern (outside the minimum or maximum limits) but is set only during the key on engine running (KOER) self test. The DTCs P0400 and P0403 are MIL codes, and the DTC P1408 is a non-MIL code.

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 run duration of 300 seconds.

During a cold start, when the thermostat should be closed, the enhanced thermostat monitor uses intake air temperature, engine rpm, vehicle speed and engine load to predict the engine coolant temperature. Once the predicted temperature reaches a calibrated temperature, the actual engine cooling temperature is compared to see if it reached the same calibrated temperature. The calibrated temperature is within 11°C (20°F) below the thermostat regulating temperature. Once the engine cooling temperature exceeds the calibrated temperature after an estimated time, the engine cooling temperature is then compared to the same calibrated temperature to determine if the engine cooling temperature has warmed up enough. If the engine cooling temperature is within the calibrated temperature, the thermostat is functioning correctly. If the engine cooling temperature is too low, the thermostat may be stuck open and DTC P0128 sets.

Evaporative Emission (EVAP) Leak Check Monitor

The EVAP leak check monitor is an on-board strategy designed to detect a leak from a hole (opening) equal to or greater than 0.508 mm (0.020 inch) in the enhanced EVAP system. The correct function of the individual components of the enhanced EVAP system, as well as its ability to flow fuel vapor to the engine, is also examined. The EVAP leak check monitor relies on the individual components of the enhanced EVAP system to either allow a natural vacuum to occur in the fuel tank or apply engine vacuum to the fuel tank and then seal the entire enhanced EVAP system from the atmosphere. The fuel tank pressure is then monitored to determine the total vacuum lost (bleed-up) for a calibrated period of time. Inputs from the cylinder head temperature (CHT) sensor, intake air temperature (IAT) sensor, mass air flow (MAF) sensor, vehicle speed, fuel level input (FLI) and fuel tank pressure (FTP) sensor are required to enable the EVAP leak check monitor.

During the EVAP leak check monitor repair verification drive cycle, clearing the continuous diagnostic trouble codes (DTCs) and resetting the emission monitors information in the powertrain control module (PCM) bypasses the minimum soak time required to complete the monitor. The EVAP leak check monitor does not run if the key is turned off after clearing the continuous DTCs and resetting the emission monitors information in the PCM. The EVAP leak check monitor does not run if a MAF sensor concern is present. The EVAP leak check monitor does not initiate until the heated oxygen sensor (HO2S) monitor is complete.

If the vapor generation is high on some vehicle enhanced EVAP systems, where the monitor does not pass, the result is treated as a no test. Therefore, the test is complete for the day.

This vehicle has an engine off natural vacuum (EONV) check as part of the EVAP leak check monitor.

Engine On EVAP Leak Check Monitor

The engine on EVAP leak check monitor is executed by the individual components of the enhanced EVAP system as follows

1. The EVAP canister purge valve is used to control the flow of vacuum from the engine and create a target vacuum on the fuel tank.
2. The canister vent (CV) solenoid is used to seal the EVAP system from the atmosphere. It is closed by the PCM (100% duty cycle) which then allows the EVAP canister purge valve to obtain the target vacuum on the fuel tank.
3. The FTP sensor is used by the engine on EVAP leak check monitor to determine if the target vacuum necessary to carry out the leak check on the fuel tank is reached. Once the target vacuum on the fuel tank is achieved, the change in fuel tank vacuum for a calibrated period of time determines if a leak exists.
4. The fuel vapor vent valve isolates the fuel tank from the rest of the EVAP system. The fuel vapor vent valve allows the flow of vapors from the fuel tank to the EVAP canister purge valve and the EVAP canister. Whenever it is desired to isolate the fuel tank from the rest of the EVAP system, the PCM provides a duty cycle signal of 100% to command the valve closed. To allow flow of fuel vapors from the fuel tank, the PCM provides 0% duty cycle and the fuel vapor vent valve opens.
5. If the initial target vacuum cannot be reached, DTC P0455 (gross leak detected) is set. The EVAP leak check monitor aborts and does not continue with the leak check portion of the test.
6. The malfunction indicator lamp (MIL) is activated for DTCs P0442, P0455, P0456, P0457, and P1450 after two occurrences of the same concern and for DTC P144A or P2450 after a sufficient number of completions. The MIL can also be activated for any enhanced EVAP system component DTCs in the same manner. The enhanced EVAP system component DTCs P0443, P0446, P0452, P0453, and P2418 are tested as part of the comprehensive component monitor (CCM).

Scheme 167

Engine Off Natural Vacuum (EONV) EVAP Leak Check Monitor

The EONV EVAP leak check monitor is executed during key off, after the engine on EVAP leak check monitor is completed. The EONV EVAP leak check monitor determines a leak is present when the naturally occurring change in fuel tank pressure or vacuum does not exceed a calibrated limit during a calibrated amount of time. A separate, low power consuming, microprocessor in the PCM manages the EONV leak check. The engine off EVAP leak check monitor is executed by the individual components of the enhanced EVAP system as follows

1. The EVAP canister purge valve is normally closed at key off.
2. The normally open canister vent (CV) remains open for a calibrated amount of time to allow the fuel tank pressure to stabilize with the atmosphere. During this time period the FTP sensor is monitored for an increase in pressure. If pressure remains below a calibrated limit the CV is closed by the PCM (100% duty cycle) and seals the EVAP system from the atmosphere.
3. The FTP sensor is used by the EONV EVAP leak check monitor to determine if the target pressure or vacuum necessary to complete the EONV EVAP leak check monitor on the fuel tank is reached. Some vehicle applications with the EONV EVAP leak check monitor use a remote inline FTP sensor. If the target pressure or vacuum on the fuel tank is achieved within the calibrated amount of time, the test is complete.
4. The EONV EVAP leak check monitor uses the naturally occurring change in fuel tank pressure to detect a leak in the EVAP system. At key off, a target pressure and vacuum is determined by the PCM. These target values are based on the fuel level and the ambient temperature at key off. As the fuel tank temperature increases, the pressure in the tank increases and as the temperature decreases a vacuum develops. If a leak is present in the EVAP system the fuel tank pressure or vacuum does not exceed the target value during the testing time period. The EONV EVAP leak check monitor begins at key off.
5. The EONV EVAP leak check monitor is controlled by a separate low power consuming microprocessor inside the PCM. The fuel level indicator, fuel tank pressure, and battery voltage are inputs to the microprocessor. The microprocessor outputs are the CV solenoid and the stored test information. If the separate microprocessor is unable to control the CV solenoid or communicate with other processors DTC P260F is set.
6. The MIL is activated for DTCs P0456 and P260F. The MIL can also be activated for any enhanced EVAP system component DTCs in the same manner. The enhanced EVAP system component DTCs P0443, P0446, P0452, and P0453, are tested as part of the CCM.

Scheme 168

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 powertrain control module (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 part 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/fuel ratio parameter called LAMBSE. LAMBSE is calculated by the PCM from the heated oxygen sensor (HO2S) inputs and helps maintain a 14.7:1 air/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 air flow (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 stoichiometric while running in the closed loop. These learned corrections are stored in the KAM as long term fuel trim (LONGFT) corrections. As components continue to change beyond normal limits, or if a concern occurs, the LONGFT reaches a calibrated rich or lean limit and the adaptive fuel strategy is no longer allowed to compensate for additional fuel system changes. LONGFT correction at their limits, in conjunction with a calibrated deviation in short term fuel trim (SHRTFT), indicate a rich or lean fuel system concern. The fuel system monitor stores the appropriate DTC when a concern is detected as described below.

1. The HO2S detects the presence of oxygen in the exhaust and provides the PCM with the feedback indicating air/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/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

1. engine coolant temperature is between 71°C - 110°C (160°F - 230°F)
2. engine speed is between 1,000 - 4,000 RPM
3. air mass range is greater than 3 g/sec (0.4 lb/min)
4. purge duty cycle of 0%

Typical fuel monitor thresholds

1. lean condition: LONGFT greater than 29%, SHRTFT greater than 1%
2. rich condition: LONGFT less than 20%, SHRTFT less than -1%

Scheme 169

Heated Oxygen Sensor (HO2S) Monitor

The HO2S monitor is an on-board strategy designed to monitor the HO2Ss for concerns or deterioration which can affect emissions. The front or stream 1 HO2S is checked for correct output voltage and response rate. Response rate is the time it takes to switch from lean to rich or rich to lean. The rear or stream 2 HO2S is monitored for correct output voltage and is used for catalyst monitoring and fore-aft oxygen sensor (FAOS) control. Input is required from the cylinder head temperature (CHT), intake air temperature (IAT), mass air flow (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 HO2S senses the oxygen content in the exhaust flow. The typical HO2S outputs a voltage between 0 and 1.0 volt. Lean of stoichiometric, air/fuel ratio of approximately 14.7:1, the HO2S generates a voltage between 0 and 0.45 volt. Rich of stoichiometric, the HO2S generates a voltage between 0.45 and 1.0 volt. The current required to maintain the universal HO2S at 0.45 volt is used by the powertrain control module (PCM) to calculate the air/fuel ratio. The HO2S monitor evaluates the HO2Ss for correct function.
2. 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 lack of switching concern may be caused by HO2S concerns or by shifts in the fuel system, diagnostic trouble codes (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 line.
3. The malfunction indicator lamp (MIL) is activated after a concern is detected on two consecutive drive cycles.

The HO2S monitor DTCs can be categorized as follows

1. P0030 - HO2S heater control
2. P0053, P0054 - HO2S heater resistance
3. P0130 - HO2S circuit concerns
4. P0132, P0138 - HO2S circuit high voltage
5. P0133 - HO2S slow response rate
6. P0134 - HO2S circuit no activity detected
7. P0135, P0141 - HO2S heater circuit
8. P013A, P013E - Rear HO2S DFSO response test
9. P1127 - downstream HO2S not running in on-demand self-test
10. P2096, P2097 - Post-catalyst fuel trim
11. P2195, P2196, P2270, P2271 - HO2S lack of switching

Scheme 170

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, poor fuel metering, poor 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 air flow (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.

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.

Scheme 171

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 value(s) 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 value(s) are also evaluated for noise. Normally, misfire results in a nonsymmetrical loss of cylinder acceleration. Mechanical noise, such as rough roads or high RPM/light load conditions, produce symmetrical acceleration variations. Cylinder events that indicate excessive deviant accelerations of this type are considered noise. 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/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(s).

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 key 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 key is turned to the OFF position (typically 1 key 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 4 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. In the event of the 12-volt battery disconnection or loss of KAM, the correction factors are lost and must be relearned. 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 monitor consists of a modified PCV system design. The PCV valve is installed into the rocker cover 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 that 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 illuminates the malfunction indicator lamp (MIL) after two consecutive driving cycles and stores one or more of the following diagnostic trouble codes (DTCs), lack of heated oxygen sensor (HO2S) switches, bank 1 (P2195), fuel system lean, bank 1 (P0171).

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

Transaxle Comprehensive Component Monitor (CCM)

The transaxle CCM monitors for concerns in the transaxle system. The transaxle CCM monitors internal and external electronic and mechanical components, as well as internal and external circuits which provide input or output signals to or from the transaxle control module (TCM). The circuitry and components are typically monitored for circuit continuity and correct range of values. Where feasible, they are also checked for rationality.

The transaxle CCM covers many components and circuits and tests them in various ways depending on the hardware, function, and type of signal. For example, input and output signals are typically checked for opens, shorts, and in-range failures. This type of monitoring is carried out continuously. Some TCM input and output signals may rely on rationality checks - checking to see if the input or output value makes sense for the current system operating conditions. These types of tests may require monitoring several components and can only be carried out under appropriate test conditions.

The following components and circuitry are monitored by the transaxle CCM. The list includes the components or other TCM inputs, corresponding circuitry, and the type of electrical test carried out.

Transaxle fluid temperature sensor and circuit

1. open circuit test
2. short circuit to ground test
3. short circuit to power test
4. in-range failure test

Motor and generator coil temperature sensors and circuits

1. open circuit test
2. short circuit to ground test
3. short circuit to power test
4. in-range failure test

Motor and generator inverter temperature sensors and circuits

1. open circuit test
2. short circuit to ground test
3. short circuit to power test
4. in-range failure test

Motor and generator current sensors and circuits

1. open circuit test
2. short circuit to ground test
3. short circuit to power test
4. in-range failure test
5. rationality test

Immediate shutdown 1 and 2 circuits

1. open circuit test
2. short circuit to ground test
3. rationality test

Motor and generator shutdown circuits

1. open circuit test
2. short circuit to ground test
3. short circuit to power test
4. rationality test

Clean tachometer output circuit

1. open circuit test
2. short circuit to ground test
3. short circuit to power test
4. rationality test

Motor and generator inverters

1. open circuit test
2. short circuit to ground test
3. short circuit to power test
4. in-range failure test
5. rationality test
6. over voltage test

High voltage interlock circuit

1. open circuit test

In addition to the electrical checks, the transaxle CCM also monitors the ignition voltage to the TCM for over voltage and under voltage conditions, traction motor and generator over-speed conditions, park pawl for mechanical damage, and an abnormal shutdown condition. The controller area network (CAN) messages such as revolutions per mile, generator mode, vehicle mode, total torque desired, engine speed desired, and estimated engine torque are monitored for out of range or missing status.

When any monitored component fails and no longer operates within manufacturer's specifications, the TCM stores the diagnostic trouble code (DTC) and illuminates the powertrain malfunction indicator (wrench) lamp or hazard lamp. When the initial concern is detected, the TCM stores the temporary DTC and records the freeze frame data. This temporary DTC is erased on the third vehicle restart after 2 consecutive detection trips with no concern. However, if the concern is still present after two consecutive detection trips, the powertrain malfunction indicator (wrench) lamp or hazard lamp may be illuminated. Once the powertrain malfunction indicator (wrench) lamp or hazard lamp is illuminated, three consecutive detection trips without a concern are required to extinguish them. Forty warm-up cycles without a concern are required to erase the DTC from the TCM memory.

In addition to the DTC stored, the TCM stores freeze frame data in the electrically erasable programmable read only memory (EEPROM). The following parameters are recorded when freeze frame data is stored

1. DTC item number
2. engine speed
3. transaxle fluid temperature
4. traction motor and generator speed
5. highest traction motor and generator inverter temperature
6. traction motor and generator coil temperature
7. desired total torque
8. desired traction motor and generator torque
9. shift position

The freeze frame data is accessible with the scan tool to assist in diagnosing the vehicle.

Variable Camshaft Timing (VCT) Monitor

The VCT output driver in the powertrain control module (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 .