Engine Controls - Description & Operation (Except Diesel & Hybrid) (Section 1): Other Ford Explorer V

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 the emissions systems.

Scheme 18

Engine/Evaporative Emission (EVAP) System Information

Manufacturers must use a standardized system for identifying their individual engine families. The system described below was developed by the Environmental Protection Agency (EPA) in 1991 to meet new regulatory requirements for 1994 and later model years.

The engine family group and evaporative family name consist of 12 characters each.

Both the engine family group and the evaporative family name are listed in the box on the emission decal in the area marked as engine evaporative family information. The first line contains 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. Refer to the Engine Family Group in (Scheme 20) and the Evaporative Family Name worksheet in (Scheme 21) for decoding information.

Scheme 19

Scheme 20

Scheme 21

Vehicle Emission Control Information (VECI) Acronym Definitions

CAC: Charge Air Cooler

CARB: California Air Resource Board

CARB LEV: Low Emission Vehicle

CARB SULEV: Super Ultra Low Emission Vehicle

CARB TLEV: Transitional Low Emission Vehicle

CARB ULEV: Ultra Low Emission Vehicle

CARB ZEV: Zero Emission Vehicle

CI: Cylinder Injection

DGI: Direct Gas Injection

EPA: Environmental Protection Agency

EVAP: Evaporative Emission

GVW: Gross Vehicle Weight

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

HHDDE: Heavy Heavy Duty Diesel Engine

HHDE: Heavy Heavy Duty Engine

HO2S: Heated Oxygen Sensor

ILEV: Inherently Low Emission Vehicle

LDDT: Light Duty Diesel Truck categories

LDT: Light Duty Truck (gasoline) categories based on weight as defined in the table.

LDV: Light Duty Vehicle, generally passenger cars and light trucks under 2, 721.55 Kg (6, 000 lb) GVWR.

LEV: Low Emission Vehicle

LEV-II: California regulations beginning in the 2004 model year.

LHDE: Light Heavy Duty Engine (several weight categories).

LVW: Loaded Vehicle Weight, curb weight plus 136.08 Kg (300 lb).

MDPV: Medium Duty Passenger Vehicle

MDT: Medium Duty Truck categories based on weight as defined in the table.

MDV: Medium Duty Vehicle

MHDDE: Medium Heavy Duty Diesel Engine

MHDE: Medium Heavy Duty Engine

MPI: Multi-Port Injection

MY: Model Year

NCP: Non-Compliance Penalty

OBD: On Board Diagnostics

ORVR: On Board Refueling Vapor Recovery

PC: Passenger Car

PZEV: Partial Zero Emission Vehicle

SFI: Sequential Multiport Fuel Injection

SI: Sequential Injection

SULEV: Super Ultra Low Emission Vehicle

TC: Turbocharged

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

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

Tier 2: Federal regulations beginning in the 2004 model year.

TWC: Three-Way Catalytic Converter

ULEV: Ultra Low Emission Vehicle

ZEV: Zero Emission Vehicle

Engine Control Components

Note. Transmission inputs which are not described in this service information are discussed in the appropriate Transaxle/Transmission article .

Accelerator Pedal Position (APP) Sensor

The APP sensor is an input to the powertrain control module (PCM) and determines the amount of torque requested by the operator. Depending on the application, either a 2 track or 3 track APP sensor is used.

Track APP Sensor - Fiesta

There are 2 separate pedal position sensors in the accelerator pedal. The APP1 sensor signal generates a pulse width modulated (PWM) signal to the PCM. The APP1 sensor uses a VPWR circuit, a ground circuit and a signal circuit. Only the APP1 signal circuit is connected to the PCM. The APP2 sensor signal has a positive slope (increasing angle, increasing voltage) and is a class 2 message from the instrument panel cluster (IPC) to the PCM. The APP2 sensor uses a reference voltage circuit, a signal return circuit, and a signal circuit between the IPC and the APP sensor assembly. The two pedal position signals make sure the PCM receives a correct input even if one of the signals has a concern. The PCM determines if a signal is incorrect by calculating an expected position, inferred from the other signals. If a concern is present with one of the circuits the other input is used. The pedal position signal is converted to pedal travel degrees (rotary angle) by the PCM. The software 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) .

2 Track APP Sensor - All Others

There are 2 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 2 pedal position signals make sure the PCM receives a correct input even if one of the signals 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 2 reference voltage circuits, 2 signal return circuits, and 2 signal circuits (a total of 6 circuits and pins) between the PCM and the APP sensor assembly. The pedal position signal is converted to pedal travel degrees (rotary angle) by the PCM. The software 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 22

3 Track APP Sensor

There are 3 pedal position signals in the sensor. Signal 1, APP1, has a negative slope (increasing angle, decreasing voltage) and signals 2 and 3, APP2 and APP3, both have a positive slope (increasing angle, increasing voltage). During normal operation, APP is used as the indication of pedal position by the strategy. The 3 pedal position signals make sure the PCM receives a correct input even if one signal has a concern. The PCM determines if a signal is incorrect by calculating where it should be, inferred from the other signals. If a concern is present with one of the circuits the other inputs are used. The pedal position signal is converted to pedal travel degrees (rotary angle) by the PCM. The software converts these degrees to counts, which is the input to the torque based strategy. There are 2 reference voltage circuits, 2 signal return circuits, and 3 signal circuits (a total of 7 circuits and pins) between the PCM and the APP sensor assembly.

Scheme 23

Ambient Air Temperature (AAT) Sensor

The AAT 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.

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

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

Scheme 24

Barometric Pressure (BARO) Sensor

The BARO sensor directly measures barometric pressure to estimate the exhaust back pressure. Exhaust back pressure influences speed density based air charge computation. The BARO sensor is mounted directly to the PCM circuit board.

Brake Pedal Position (BPP) Switch

The BPP switch is sometimes referred to as the stoplamp switch. The BPP switch provides a signal to the PCM indicating the brakes are applied. The BPP switch is normally open and mounted on the brake pedal support. Depending on the vehicle application the BPP switch can be hardwired as follows

Scheme 25

1. to the PCM supplying battery positive (B+) voltage when the brake pedal is applied.
2. to the anti-lock brake system (ABS) module, or lighting control module (LCM), the BPP signal is then broadcast over the network to be received by the PCM.
3. to the ABS traction control/stability assist module. The ABS module interprets the BPP switch input along with other ABS inputs and generates an output called the driver brake application (DBA) signal. The DBA signal is then sent to the PCM and to other BPP signal users.

Brake Pressure Switch

The brake pressure switch is used for vehicle speed control deactivation. A normally closed switch supplies battery positive (B+) voltage to the PCM when the brake pedal is not applied. When the brake pedal is applied, the normally closed switch opens and power is removed from the PCM.

On some applications the normally closed brake pressure switch, along with the normally open BPP switch, are used for a brake rationality test within the PCM. The PCM misfire monitor profile learn function may be disabled if a brake switch concern occurs. If one or both brake pedal inputs to the PCM is not changing states as expected, a diagnostic trouble code (DTC) is set by the PCM strategy.

Camshaft Position (CMP) Sensor

The CMP sensor 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. Coil on plug (COP) ignition applications use the CMP signal to select the correct ignition coil to fire.

Inline engines with 2 camshafts and with variable camshaft timing (VCT) are equipped with 2 CMP sensors. The second sensor identifies the position of the exhaust camshaft.

The 2 sensor system on inline engines use the following CMP signal circuit names

1. CMP11 - bank 1, intake camshaft
2. CMP12 - bank 1, exhaust camshaft

Engines with 1 camshaft per bank and with VCT are equipped with 2 CMP sensors. The second sensor identifies the position of the camshaft on bank 2.

The 2 sensor system on engines with 1 camshaft per bank and with VCT use the following CMP signal circuit names

1. CMP1 - bank 1
2. CMP2 - bank 2

Engines with 4 camshafts and with VCT are equipped with 4 CMP sensors. The 4 sensors identify the position of each camshaft.

The 4 sensor system uses the following CMP signal circuit names

1. CMP11 - bank 1, intake camshaft
2. CMP12 - bank 1, exhaust camshaft
3. CMP21 - bank 2, intake camshaft
4. CMP22 - bank 2, exhaust camshaft

There are the 2 types of CMP sensors used. The 2 pin variable reluctance sensor and the 3 pin Hall effect sensor.

Scheme 26

Scheme 27

Charge Air Cooler Temperature (CACT) Sensor

The CACT sensor is located in the intake air tube between the charge air cooler (CAC) and the throttle body. The CACT sensor measures the throttle inlet temperature. The PCM uses the CACT sensor information to refine the estimate of the airflow rate through the throttle and to determine the desired boost pressure. The CACT sensor for a speed density system is integrated with the turbocharger boost pressure (TCBP) sensor.

Scheme 28

Check Fuel Cap Indicator

The check fuel cap indicator is a communications network message sent by the PCM. The PCM sends the message to illuminate the lamp when the strategy determines there is a concern in the EVAP system due to the fuel filler cap or capless fuel tank filler pipe not being sealed correctly. This is detected by the inability to pull vacuum in the fuel tank after a fueling event.

Clutch Pedal Position (CPP) Switch

The CPP switch is an input to the PCM indicating the clutch pedal position. The PCM provides a low current voltage on the CPP circuit. When the CPP switch is closed, this voltage is pulled low through the signal return (SIGRTN) circuit. The CPP input to the PCM is used to detect a reduction in engine load. The PCM uses the load information for mass airflow and fuel calculations.

Scheme 29

Coil On Plug (COP)

The COP ignition operates similar to a standard coil pack ignition except each plug has 1 coil per plug. The COP operates in engine crank, engine running and camshaft position failure mode effects management (FMEM) modes. The COP eliminates the need for secondary spark plug wires which improves reliability. Currently there are two types of COP in use today. The first type of COP is a 2 circuit system that consists of the coil and boot that is installed directly on top of the spark plug which is fired by a driver located in the PCM.

The second type COP is a 3 circuit system with the driver integrated in the COP assembly that is triggered when the PCM supplies the signal to fire. This configuration eliminates the need for high current lines from the PCM to the COP. For additional information, refer to IGNITION SYSTEMS .

Scheme 30

Scheme 31

Coil Pack

The PCM provides a grounding switch for the coil primary circuit. When the switch is closed, voltage is applied to the coil primary circuit. This creates a magnetic field around the primary coil. The PCM opens the switch, causing the magnetic field to collapse, inducing the high voltage in the secondary coil windings and firing the spark plug. The spark plugs are paired so that as 1 spark plug fires on the compression stroke, the other spark plug fires on the exhaust stroke. The next time the coil is fired the order is reversed. The next pair of spark plugs fire according to the engine firing order.

Coil packs come in 4-tower, 6-tower horizontal and 6-tower series 5 models. Two adjacent coil towers share a common coil and are called a matched pair. For 6-tower coil pack (6 cylinder) applications, the matched pairs are 1 and 5, 2 and 6, and 3 and 4. For 4-tower coil pack (4 cylinder) applications, the matched pairs are 1 and 4 and 2 and 3.

When the coil is fired by the PCM, spark is delivered through the matched pair towers to their respective spark plugs. The spark plugs are fired simultaneously and are paired so that as one fires on the compression stroke, the other spark plug fires on the exhaust stroke. The next time the coil is fired, the situation is reversed. The next pair of spark plugs fire according to the engine firing order.

Scheme 32

Scheme 33

Cooling Fan Clutch

The cooling fan clutch is an electrically actuated viscous clutch that consists of 3 main elements

1. a working chamber
2. a reservoir chamber
3. a cooling fan clutch actuator valve and a fan speed sensor (FSS)

The cooling fan clutch actuator valve controls the fluid flow from the reservoir into the working chamber. Once viscous fluid is in the working chamber, shearing of the fluid results in fan rotation. The cooling fan clutch actuator valve is activated with a pulse width modulated (PWM) output signal from the PCM. By opening and closing the fluid port valve, the PCM can control the cooling fan speed. The cooling fan speed is measured by a Hall effect sensor and is monitored by the PCM during closed loop operation.

The PCM optimizes fan speed based on engine coolant temperature, engine oil temperature, transmission fluid temperature, intake air temperature, or air conditioning requirements. When an increased demand for fan speed is requested for vehicle cooling, the PCM monitors the fan speed through the Hall effect sensor. If a fan speed increase is required, the PCM outputs the PWM signal to the fluid port, providing the required fan speed increase.

Scheme 34

Cooling Fan Control

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

For Edge, Flex, Focus, Fusion, MKS, MKT, MKX, MKZ, Taurus, variable speed electric fans

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

The fan controller has the capability to detect certain failure modes within the fan motors. Under certain failure modes, such as a motor that is drawing excessive current, the fan controller shuts OFF the fans. Fan motor concerns may not set a specific DTC. With the fan motor disconnected from the fan controller, voltage may not be present at the fan controller.

EDGE, FLEX, FOCUS, FUSION, MKS, MKT, MKX, MKZ, TAURUS FCV DUTY CYCLE OUTPUT FROM PCM (NEGATIVE DUTY CYCLE)

For Mustang, F-150, Navigator, Expedition, Escape, Transit Connect, relay controlled fans

The PCM controls the fan operation through the fan control (FC), (single speed fan applications), low fan control (LFC) and high fan control (HFC) outputs. Some applications have the xFC circuit wired to 2 separate relays.

For 2-speed fans, although the PCM output circuits are called low and high fan control, cooling fan speed is controlled by a combination of these outputs. Refer to the following tables.

TRANSIT CONNECT (WITH A/C) PCM FC OUTPUT STATE FOR COOLING FAN SPEEDS

2.5L ESCAPE PCM FC OUTPUT STATE FOR COOLING FAN SPEEDS

MUSTANG PCM FC OUTPUT STATE FOR COOLING FAN SPEEDS

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 sensor is the primary sensor for ignition information to the PCM. The pulse wheel for some V6 engines and V8 engines have a total of 35 teeth spaced 10 degrees apart with 1 empty space for a missing tooth. The pulse wheel for some 4 cylinder engines and some V6 engines have a total of 58 teeth spaced 6 degrees apart with 2 empty spaces. The 6.8L 10 cylinder pulse wheel has 39 teeth spaced 9 degrees apart and one 9 degree empty space for a missing tooth. By monitoring the pulse wheel, the CKP sensor signal indicates 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 for the CKP sensor configuration. The PCM also uses the CKP sensor signal to determine if a misfire has occurred by measuring rapid decelerations between teeth.

There are the 2 types of CKP sensors used. The 2 pin variable reluctance sensor and the 3 pin Hall effect sensor.

Scheme 35

Cylinder Head Temperature (CHT) Sensor

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

The CHT sensor is a thermistor device in which resistance changes with the temperature. The electrical resistance of a thermistor decreases as temperature increases, and the resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so varying the resistance of the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor (pull-up resistor) in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The CHT sensor is installed in the cylinder head and measures the metal temperature. The CHT sensor provides complete engine temperature information and is used to infer coolant temperature. If the CHT sensor conveys an overheating condition to the PCM, the PCM initiates a fail-safe cooling strategy based on information from the CHT sensor. A cooling system concern, such as low coolant or coolant loss, could cause an overheating condition. As a result, damage to major engine components could occur. Using both the CHT sensor and fail-safe cooling strategy, the PCM prevents damage by allowing air cooling of the engine and limp home capability. For additional information, refer to POWERTRAIN CONTROL SOFTWARE for Fail-Safe Cooling Strategy.

Scheme 36

Differential Pressure Feedback Exhaust Gas Recirculation (EGR) Sensor

The differential pressure feedback EGR sensor is a piezo resistive type pressure transducer that monitors the differential pressure across a metering orifice. The differential pressure feedback EGR sensor receives this signal through 2 hoses referred to as the downstream pressure hose and upstream pressure hose (note the upstream pressure hose uses a larger diameter hose). The differential pressure feedback EGR sensor outputs a voltage proportional to the pressure drop across the metering orifice and supplies it to the PCM as EGR flow rate feedback.

Electric Exhaust Gas Recirculation (EEGR) Valve

Depending on the application, the EEGR valve is either a water cooled or an air 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 built-in spring works to close the valve against the motor opening force.

Scheme 37

Electronic Throttle Actuator Control (TAC)

The electronic TAC is a DC motor controlled by the PCM. There are 2 designs for the TAC, parallel and inline. The parallel design has the motor under the bore parallel to the plate shaft. The motor housing is integrated into the main housing. The inline design has a separate motor housing. Both designs use an internal spring to return the throttle plate to a default position. The default position is typically a throttle angle of 7 to 8 degrees from the hard stop angle. The closed throttle plate hard stop prevents the throttle from binding in the bore. This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle. For additional information, refer to TORQUE BASED ELECTRONIC THROTTLE CONTROL (ETC) .

Scheme 38

Scheme 39

Electronic Throttle Body Throttle Position Sensor (ETBTPS)

The ETBTPS has two signal circuits in the sensor for redundancy. The redundant ETBTPS signals are required for increased monitoring. The first ETBTPS 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 ETBTPS signals make sure the PCM receives a correct input even if one signal has a concern. For Fiesta, there is one reference voltage circuit (ETCREF) and one signal return circuit (ETCRTN) for the sensor dedicated to the ETBTPS. For all others, there is one reference voltage circuit (ETCREF) and one signal return circuit (ETCRTN) for the sensor shared with the reference voltage circuits (APPVREF and APPVREF2) and signal return circuits (APPRTN and APPRTN2) used by the APP sensor. For additional information, refer to TORQUE BASED ELECTRONIC THROTTLE CONTROL (ETC) .

Engine Coolant Temperature (ECT) Sensor

The ECT 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 changes the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so varying the resistance of the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor (pull-up resister) in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The ECT sensor measures the temperature of the engine coolant. The PCM uses the engine coolant temperature input for fuel control and for cooling fan control. The ECT sensor can be a threaded or twist lock type. The ECT sensor is located in an engine coolant passage.

Scheme 40

Evaporative Emission (EVAP) Canister Vent Valve

The EVAP canister vent valve (located near the EVAP canister) is part of the enhanced EVAP system controlled by the PCM. During the EVAP leak check monitor, the EVAP canister vent valve seals the EVAP canister from the atmospheric pressure. This allows the EVAP purge valve to achieve the target vacuum in the fuel tank during the EVAP leak check monitor.

Scheme 41

EVAP Check Valve

The EVAP check valve is used on turbocharged engines to prevent boost pressure from forcing open the EVAP purge valve and entering the EVAP system. The valve is open under normal engine vacuum. The valve closes during boost conditions to prevent the fuel tank from being pressurized and hydrocarbons forced out of the EVAP system into the atmosphere through the EVAP canister vent valve. When the engine is OFF, or at atmospheric pressure, the EVAP check valve is in an indeterminate state. The EVAP check valve is an integral part of the EVAP purge valve assembly.

Scheme 42

EVAP Dual Check Valve

The EVAP dual check valve is used to allow purge flow during boost conditions. Fuel vapors flow through the EVAP dual check valve to the intake air system upstream of the turbocharger before entering the intake manifold. When the engine is OFF, or at atmospheric pressure, the EVAP dual check valve is in an indeterminate state.

Scheme 43

Evaporative Emission (EVAP) Ejector

The EVAP ejector is used on turbocharged engines to create a vacuum in the EVAP purge line from the EVAP purge valve to the intake air system. During boost conditions, boost pressure flows through a venturi inside the EVAP ejector creating a vacuum in the EVAP purge line to the intake air inlet to the turbocharger. When the second EVAP check valve is open, the purge vapor is drawn through the EVAP ejector into the intake air tube, through the turbocharger and charge air cooler, to the intake manifold.

Scheme 44

Evaporative Emission (EVAP) Natural Vacuum Leak Detection (NVLD) Module

The NVLD module is located in the EVAP canister vent hose, under the vehicle. Battery voltage (VBAT) is supplied to the NVLD module to allow EVAP system diagnostics to run after the ignition is turned OFF. The NVLD module electrical connector also incorporates a communication (NVLD) circuit and a ground (GND) circuit between the NVLD module and the PCM.

Internal to the NVLD module is a normally open vacuum switch (closes with vacuum), a normally closed vacuum relief valve (opens with excessive vacuum), a normally closed pressure relief valve (opens during refueling), an internal ambient air temperature sensor and a timer. The NVLD module completes a series of checks to confirm the integrity of the enhanced EVAP system components in the engine running state and the ignition OFF state. When the ignition is turned ON and the engine is running the NVLD module sends the information stored during the ignition OFF tests to the PCM.

Scheme 45

Evaporative Emission (EVAP) Purge Valve

The EVAP purge valve (located near the engine) is part of the enhanced EVAP system 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 purge valve is a normally closed valve. The EVAP purge valve controls the flow of vapors, eliminating the need for an electronic vacuum regulator and vacuum diaphragm. For Flex 3.5L 4V, Fusion 3.5L, MKS 3.7L, MKT 3.7L, MKZ 3.5L, Taurus 3.5L 4V and Transit Connect the PCM outputs a variable current between 0 and 1, 000 mA to control the EVAP purge valve. For all others, the PCM outputs a duty cycle between 0% and 100% to control the EVAP purge valve.

Scheme 46

Exhaust Gas Recirculation (EGR) System Module (ESM)

The ESM functions in the same manner as a conventional differential pressure feedback EGR system. The various system components have been integrated into a single component called the ESM. The flange of the valve portion of the ESM bolts directly to the intake manifold with a metal gasket that forms the metering orifice. This arrangement increases system reliability, response time, and system precision. By relocating the EGR orifice from the exhaust to the intake side of the EGR valve, the downstream pressure signal measures manifold absolute pressure. This manifold absolute pressure signal is used for EGR correction and inferred barometric pressure (BARO) at ignition ON. The system provides the PCM with a differential pressure feedback EGR signal that is identical to a traditional differential pressure feedback EGR system.

Scheme 47

Exhaust Gas Recirculation (EGR) Vacuum Regulator Solenoid

The EGR vacuum regulator solenoid is an electromagnetic device used to regulate the vacuum supply to the EGR valve. The solenoid contains a coil which magnetically controls the position of a disc to regulate the vacuum. As the duty cycle to the coil increases, the vacuum signal passed through the solenoid to the EGR valve also increases. Vacuum not directed to the EGR valve is vented through the solenoid vent to the atmosphere. At 0% duty cycle (no electrical signal applied), the EGR vacuum regulator solenoid allows some vacuum to pass, but not enough to open the EGR valve.

Scheme 48

EGR VACUUM REGULATOR SOLENOID DATA

Exhaust Gas Recirculation (EGR) Valve

The EGR valve in the differential pressure feedback EGR system is a conventional, vacuum-actuated valve. The valve increases or decreases the EGR flow. As vacuum applied to the EGR valve diaphragm overcomes the spring force, the valve begins to open. As the vacuum signal weakens, at 5.4 kPa (1.6 in-Hg) or less, the spring force closes the valve. The EGR valve is fully open at approximately 15 kPa (4.4 in-Hg).

Since EGR flow requirement varies greatly, providing repair specifications on flow rate is impractical. The on board diagnostic (OBD) system monitors the EGR valve function and triggers a DTC if the test criteria is not met. The EGR valve flow rate is not measured directly as part of the diagnostic procedures.

Scheme 49

Fan Speed Sensor (FSS)

The FSS is a Hall effect sensor that measures the cooling fan clutch speed by generating a waveform with a frequency proportional to the fan speed. If the cooling fan clutch is moving at a relatively low speed, the sensor produces a signal with a low frequency. As the cooling fan clutch speed increases, the sensor generates a signal with a higher frequency. The PCM uses the frequency signal generated by the FSS as a feedback for closed loop control of the cooling fan clutch. For additional information on the cooling fan clutch, refer to the COOLING FAN CLUTCH .

Fuel Injection Pump

Note. Do not apply battery positive (B+) voltage directly to the fuel volume regulator solenoid electrical connector terminals. Internal damage to the solenoid may occur in a matter of seconds.

The engine driven fuel injection pump increases fuel rail pressure to the desired level to support fuel injection requirements. Unlike conventional port fuel injection systems, with direct injection the desired fuel rail pressure ranges widely over operating conditions. The pump receives fuel from the fuel pump (FP) assembly, increases the fuel pressure from approximately 448 kPa (65 psi) to a variable pressure up to 15 MPa (2175 psi), and delivers it to the fuel rails. The fuel injection pump is driven by a dedicated intake camshaft lobe and is located on top of the engine.

The fuel volume regulator is a solenoid valve permanently mounted to the pump assembly. The PCM commands the fuel volume regulator to meter in a specified fuel volume with each pump stroke. The PCM regulates the fuel volume entering the rail to achieve the desired fuel rail pressure.

The fuel volume regulator control is synchronous to the cam position on which the pump is mounted. The fuel volume regulator control takes into account that camshaft phasing varies during engine operation for purposes of valve control.

Scheme 50

Fuel Injectors

Note. Do not apply battery positive (B+) voltage directly to the fuel injector electrical connector terminals. Internal damage to the solenoid may occur in a matter of seconds.

The fuel injector is a solenoid-operated valve that meters fuel flow to the engine. The fuel injector opens and closes 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 either the PCM power relay or fuel pump relay. The ground signal is controlled by the PCM.

The injector is a 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.

Scheme 51

Fuel Injectors - Direct Injection

The gasoline direct fuel injection fuel injector delivers fuel directly into the cylinder under high pressure. Each injector is controlled by 2 circuits from the PCM.

A boosted voltage supply, up to 65 volts, is generated in the PCM and used to initially open the injector. The injector driver controls three transistor switches that apply the boost voltage to open the injector and then modulates the current to hold the injector open. If boost voltage is unavailable, the correct injector opening current may not be generated in the time required.

The PCM contains a smart driver that monitors and compares high side and low side injector currents to diagnose numerous concerns. Each fuel injector high side circuit is paired inside the PCM with another fuel injector high side circuit. All injector concerns are reported with a single DTC per injector.

Scheme 52

Fuel Pressure Sensor

The fuel pressure sensor (located in the fuel line near the fuel tank) provides a pressure feedback signal for the low pressure fuel system to the PCM. The PCM uses the FLP signal to determine correct operation of the low pressure fuel system.

Scheme 53

Fuel Rail Pressure (FRP) Sensor

The FRP sensor is a diaphragm strain gauge device. The FRP sensor measures the pressure difference between the fuel rail and atmospheric pressure. The FRP sensor nominal output varies between 0.5 and 4.5 volts, with 0.5 volts corresponding to 0 MPa (0 psi) gauge and 4.5 volts corresponding to 26 MPa (3771 psi) gauge. The sensor can read vacuum and may lower the output voltage to slightly below 0.5 volts. This condition is normal and is usually the case after several hours of cold soak before the vehicle dome light is turned ON. The FP assembly is energized at the same time the dome light is commanded ON. A disabled or malfunctioning dome light does not affect the FP assembly control.

The FRP sensor is located on the fuel rail, and provides a feedback signal to indicate the fuel rail pressure to the PCM. The PCM uses the FRP signal to command the correct injector timing and pulse width for correct fuel delivery at all speed and load conditions. The FRP sensor, along with the fuel volume regulator (part of the fuel injection pump), form a closed loop fuel pressure control system. An electrically faulted FRP sensor results in the deactivation of the fuel injection pump. Fuel pressure to injectors is then provided only by the FP assembly. When the fuel injection pump is de-energized and the injectors are active, the fuel rail pressure is approximately 70 kPa (10 psi) lower than FP assembly pressure due to the pressure drop across the fuel injection pump. Thus, if the FP assembly pressure is 448 kPa (65 psi), then the fuel rail pressure would be approximately 379 kPa (55 psi) if the injectors are active.

Scheme 54

Fuel Rail Pressure Temperature (FRPT) Sensor

The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail and sends these signals to the PCM. The sensor uses the intake manifold vacuum as a reference to determine the pressure difference between the fuel rail and the intake manifold. The relationship between fuel pressure and fuel temperature is used to determine the possible presence of fuel vapor in the fuel rail.

The temperature sensing portion of the FRPT sensor is a thermistor device in which resistance changes with temperature. The electrical resistance of the thermistor decreases as the temperature increases, and the resistance increases as the temperature decreases. The varying resistance changes the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.

Both the pressure and temperature signals control the speed of the fuel pump. The speed of the fuel pump sustains fuel rail pressure which preserves fuel in its liquid state. The dynamic range of the fuel injectors increase because of the higher rail pressure, which allows the injector pulse width to decrease.

Scheme 55

Fuel Tank Pressure (FTP) Sensor

The in tank FTP sensor or the inline FTP sensor measures the fuel tank pressure.

Scheme 56

Scheme 57

Heated Oxygen Sensor (HO2S)

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

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

Scheme 58

Inertia Fuel Shutoff (IFS) Switch

The IFS switch is used in conjunction with the electric fuel pump. The IFS switch shuts OFF the fuel pump if a collision occurs. It consists of an inverted pendulum mass that is retained in a conical cone through a set of linear springs. When a sharp impact occurs, the pendulum shifts out of the conical cone, opens the circuit and shuts OFF the electric fuel pump. Once the switch is open, it must be manually reset before restarting the vehicle.

Scheme 59

Intake Air Temperature (IAT) Sensor

The IAT 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.

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor in 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, spark, and airflow.

The IAT sensor provides a quicker temperature change response time than the ECT or CHT sensor.

Currently there are 2 types of IAT sensors used, a stand alone and an integrated type. Both types function the same, however the integrated type is incorporated into the mass airflow (MAF) sensor or the turbocharger intake pressure and temperature (TCIPT) sensor instead of being a stand alone sensor.

Supercharged vehicles use 2 IAT sensors. Both sensors are thermistor type devices and operate as described above. One is located before the supercharger at the air cleaner for standard OBD and cold weather input, while the second sensor, intake air temperature 2 (IAT2), is located after the supercharger in the intake manifold. The IAT2 sensor located after the supercharger provides air temperature information to the PCM to control spark and to help determine charge air cooler (CAC) efficiency.

The IAT2 sensor for speed density control systems is centrally located on the intake manifold. The IAT2 sensor measures the intake manifold temperature. The PCM uses the information from the IAT2 sensor to determine the speed density air charge and provide input for various spark control functions. The IAT2 sensor for a speed density system is integrated with the MAP sensor.

Scheme 60

Scheme 61

Scheme 62

Intake Manifold Tuning Valve (IMTV)

The IMTV is a motorized actuated unit mounted directly to the intake manifold. The IMTV actuator controls a shutter device attached to the actuator shaft. There is no monitor input to the PCM with this system to indicate shutter position.

The motorized IMTV unit is not energized below a calibrated RPM. The shutter is in the closed position to prevent airflow blend from occurring in the intake manifold. The motorized unit is energized above a calibrated RPM. The motorized unit is commanded ON by the PCM initially at a 100 percent duty cycle to move the shutter to the open position, and then falling to approximately 50 percent to continue to hold the shutter open.

Knock Sensor (KS)

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

Scheme 63

Manifold Absolute Pressure (MAP) Sensor

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

The MAP sensor for speed density control systems is centrally located on the intake manifold and measures the intake manifold pressure. The PCM uses this information to determine the speed density air charge and to provide input for various spark control functions. The MAP sensor for a speed density system is integrated with the IAT2 sensor.

Scheme 64

Mass Airflow (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. The current required to maintain the temperature of the hot wire is proportional to the mass airflow. The MAF sensor then outputs a 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 to fuel ratio. This input is also used in determining transmission electronic pressure control (EPC), shift, and torque converter clutch (TCC) scheduling.

The MAF sensor is located near the air cleaner assembly. Most MAF sensors have an integrated IAT sensor.

Scheme 65

Output Shaft Speed (OSS) Sensor

The OSS sensor provides the PCM with information about the rotational speed of an output shaft. The PCM uses the information to control and diagnose powertrain behavior. In some applications, the sensor is also used as the source of vehicle speed. The sensor may be physically located in different places on the vehicle, depending upon the specific application. The design of each speed sensor is unique and depends on which powertrain control feature uses the information that is generated.

Power Steering Pressure (PSP) Sensor

The PSP sensor monitors the hydraulic pressure within the power steering system. The PSP sensor voltage input to the PCM changes as the hydraulic pressure changes. The PCM uses the input signal from the PSP sensor to compensate for additional loads on the engine by adjusting the idle RPM and preventing engine stall during parking maneuvers. Also, the PSP sensor signals the PCM to adjust the transmission EPC pressure during increased engine load, such as during parking maneuvers.

Scheme 66

Power Steering Pressure (PSP) Switch

The PSP switch monitors the hydraulic pressure within the power steering system. The PSP switch is a normally closed switch that opens as the hydraulic pressure increases. The PCM provides a low current voltage on the PSP circuit. When the PSP switch is closed, this voltage is pulled low through the SIGRTN circuit. The PCM uses the input signal from the PSP switch to compensate for additional loads on the engine by adjusting the idle RPM and preventing engine stall during parking maneuvers. Also, the PSP switch signals the PCM to adjust the transmission EPC pressure during increased engine load, such as during parking maneuvers.

Scheme 67

Power Take-Off (PTO) Switch And Circuits

The PTO circuit is used by the PCM to disable some of the OBD monitors during PTO operation. The PTO switch is normally open. When the PTO unit is activated, the PTO switch is closed and battery voltage is supplied to the PTO input circuit. This indicates to the PCM that an additional load is being applied to the engine. The PTO indicator lamp illuminates when the PTO system is functioning correctly and flashes when the PTO system is damaged.

When the PTO unit is activated, the PCM disables some OBD monitors which may not function reliably during PTO operation. Without the PTO circuit information to the PCM, false DTCs may be set during PTO operation. Prior to an inspection/maintenance (I/M) test, operate the vehicle with the PTO disengaged long enough to successfully complete the OBD monitors.

Throttle Position (TP) Sensor

The TP sensor provides a signal to the PCM that is linearly proportional to the throttle plate position. The TP sensor is mounted on the throttle body. As the TP sensor is rotated by the throttle shaft, the following operating conditions are determined by the PCM

Scheme 68

1. closed throttle (includes idle or deceleration)
2. part throttle (includes cruise or moderate acceleration)
3. wide open throttle (includes maximum acceleration or de-choke on crank)
4. throttle angle rate

Turbocharger

The turbocharger assembly is an exhaust driven centrifugal compressor. Expanding exhaust gases drive the turbine shaft assembly to speeds over 100, 000 RPM. The turbocharger increases the power output of an engine by increasing the mass of air entering the engine.

Two types of turbocharger are currently being used.

The first turbocharger has an integrated wastegate.

Scheme 69

The second type of turbocharger has an integrated bypass valve in the turbocharger housing.

Scheme 70

Scheme 71

Turbocharger Boost Pressure (TCBP) Sensor

The TCBP sensor is located in the intake air tube between the CAC and the throttle body. The TCBP sensor measures the throttle inlet pressure. The PCM uses the information from the TCBP sensor to refine the estimate of the airflow rate through the throttle and to determine the desired boost pressure. The TCBP sensor for a speed density system is integrated with the CACT sensor.

Turbocharger Bypass (TCBY) Valve

The TCBY valve(s) prevent back flow through the turbochargers when the throttle is rapidly closed to avoid undesirable noise. The high pressure downstream of the turbocharger is vented back to the intake air stream when the valve is open reducing pressure in the system.

Two types of bypass valves are currently being used. The first is a solenoid controlled valve located in a crossover tube between the turbocharger intake side and the pressurized output to the charge air cooler (CAC). The second type of bypass valve is an electropneumatically controlled system consisting of a vacuum source, control solenoid, tubing and a vacuum controlled bypass valve that is integrated into the turbocharger housing.

Scheme 72

Turbocharger Intake Pressure And Temperature (TCIPT) Sensor

The TCIPT sensor is located in the intake air tube between the air filter assembly and the turbocharger. The TCIPT sensor measures the turbocharger intake pressure and temperature. The PCM uses the information from the TCIPT sensor to determine if the airflow to the turbocharger is being restricted by a clogged air filter or other debris. The TCIPT sensor is integrated with an IAT sensor.

Turbocharger (TC) Wastegate Regulating Valve Solenoid

The TC wastegate regulating valve solenoid allows the PCM to indirectly control the turbocharger wastegates. The TC wastegate regulating valve solenoid controls the feedback pressure to a pneumatically powered wastegate diaphragm in order to control the boost pressure limit. When the compressor outlet pressure is allowed to increase, a pneumatically powered actuator opens each turbocharger wastegate and limits compressor outlet pressure.

The TC wastegate regulating valve solenoid supplies pressure to the pneumatically powered wastegate diaphragm, which regulates the maximum boost pressure to a constant value. A pressure greater than 35.5 kPa (5 psi) on the pneumatically powered wastegate diaphragm opens the wastegate. The TC wastegate regulating valve solenoid can partially vent (reduce) the control pressure, resulting in increased regulated maximum boost.

A duty cycle of 100% vents feedback pressure to the intake air supply, eliminating any boost limit control by the wastegate. A duty cycle of 0% results in the base boost limit.

Scheme 73

Universal Heated Oxygen Sensor (HO2S)

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

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

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

The universal HO2S heater is embedded with the sensing element allowing the engine to enter closed loop operation sooner. The heating element heats the sensor to a temperature of 780°C to 830°C (1, 436°F to 1, 526°F). The VPWR circuit supplies voltage to the heater. The PCM controls the heater ON and OFF by providing the ground to maintain the sensor at the correct temperature for maximum accuracy.

Scheme 74

Vehicle Speed Sensor (VSS)

The VSS is a variable reluctance or Hall effect sensor that generates a waveform with a frequency that is proportional to the speed of the vehicle. If the vehicle is moving at a relatively low speed, the sensor produces a signal with a low frequency. As the vehicle velocity increases, the sensor generates a signal with a higher frequency. The PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as fuel injection, ignition control, transmission shift scheduling, and TCC scheduling.

Scheme 75

Wastegate Vacuum Sensor

The wastegate vacuum sensor is an absolute pressure sensor that provides the PCM an analog voltage output that is proportional to the applied vacuum. The wastegate vacuum sensor is located near the turbocharger and the turbocharger wastegate regulating valve solenoid. The wastegate vacuum sensor measures the vacuum supplied by the turbocharger wastegate regulating valve solenoid to the wastegate actuator. The PCM uses the information from the wastegate vacuum sensor to determine the amount of vacuum being applied to the wastegate actuator.

Scheme 76

Modifications To OBD Vehicles

Modifications or additions to the vehicle may cause incorrect operation of the OBD system. Install anti-theft systems, remote starters, cellular telephones and aftermarket radios carefully. Do not install these devices by tapping into or running wires close to the powertrain control system wires or components.

Powertrain Control Module (PCM)

The center of the engine control (EC) system is a microprocessor called the PCM. The PCM receives input from sensors and other electronic components (switches, relays). Based on the information received and programmed into its memory, the PCM generates output signals to control various relays, solenoids and actuators. There are several different types of PCMs in use for this model year. Refer to the Vehicle PCM Application Table below for PCM types and their applications.

VEHICLE PCM APPLICATION CHART

Fuel Pump Control Module

Note. The Mustang 5.4L uses 2 fuel pump control modules to control fuel for the fuel delivery system. The PCM outputs only one fuel pump duty cycle on the fuel pump control (FPC) circuit. Both fuel pump control modules use this circuit. The PCM individually monitors the fuel pump control modules through the FPM and FPM2 circuits. The fuel pump control module located on the driver side of the luggage compartment is referred to as Fuel Pump Control Module 1 and the fuel pump control module located on the passenger side of the luggage compartment is referred to as Fuel Pump Control Module 2.

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 (FPM) circuit. For additional information on the fuel pump control and the fuel pump monitor, refer to FUEL SYSTEMS .

On vehicles with gasoline direct fuel injection, the high pressure fuel system may be under vacuum after several hours of cold soak. Fuel vapor may collect at the fuel injection pump, causing a long start condition. To prevent this, the fuel pump relay is energized for 1 or 2 seconds, depending on application, as soon as the dome light is commanded ON. This causes the fuel pump control module and the fuel pump to cycle for 1 or 2 seconds and purge any trapped air or fuel vapor from the high pressure fuel system.

Fuel Pump Driver Module (FPDM)

The FPDM receives a duty cycle signal from the PCM and controls the fuel pump operation in relation to this duty cycle. This results in variable speed fuel pump operation. The FPDM controls the fuel pump by switching the fuel pump return circuit ON and OFF at the required duty cycle. The FPDM sends diagnostic information to the PCM on the FPM circuit. For additional information on the fuel pump control and the fuel pump monitor, refer to FUEL SYSTEMS .

Keep Alive Memory (KAM)

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

Accelerator Pedal Position Reference Voltage (APPVREF)

APPVREF is a consistent positive voltage (5 volts plus or minus 0.5 volt) circuit.

Accelerator Pedal Position Return (APPRTN)

APPRTN is a return path for APPVREF circuit.

Electronic Throttle Control Reference Voltage (ETCREF)

ETCREF is a consistent positive voltage (5 volts plus or minus 0.5 volt) circuit.

Electronic Throttle Control Return (ETCRTN)

ETCRTN is a return path for ETCREF circuit.

Gold Plated Pins

Note. Gold plated terminals should only be replaced with new gold plated terminals.

Some engine control hardware has gold plated pins within the connectors and mating harness connectors to improve electrical stability for low current draw circuits and to enhance corrosion resistance. The engine control (EC) components equipped with gold terminals vary by vehicle application.

Keep Alive Power (KAPWR)

KAPWR provides a constant voltage input independent of ignition switch state to the PCM. This voltage is used by the PCM to maintain the KAM.

Mass Airflow Return (MAFRTN)

The MAFRTN is a signal return circuit from the MAF sensor.

Power Ground (PWRGND)

The PWRGND circuit(s) provides a return path for the PCM vehicle power (VPWR) circuits.

Signal Return (SIGRTN)

SIGRTN is a dedicated return path for VREF applied components.

Starter Motor Request (SMR) Circuit

The SMR circuit provides the PCM with a signal from the ignition switch to the PCM. The input is pulled high when the ignition is in the START position and the transmission range (TR) sensor ignition lockout circuit allows the starter to engage.

Variable Reluctance Sensor Return (VRSRTN)

The VRSRTN circuit is a dedicated return path for variable reluctance (VR) type sensors.

Vehicle Buffered Power (VBPWR)

VBPWR is a regulated voltage supplied by the PCM to vehicle sensors. These sensors require a constant 12 volts for operation and cannot withstand VPWR voltage variations. VBPWR is regulated to VPWR minus 1.5 volts and is also current limited to protect the sensors.

Vehicle Power (VPWR)

VPWR is the primary source of PCM power. VPWR is switched through the PCM power relay.

Vehicle Reference Voltage (VREF)

VREF is a consistent positive voltage (5 volts plus or minus 0.5 volt) provided by the PCM. VREF is typically used by 3-wire sensors and some digital input signals.

Adaptive Airflow

Some vehicles equipped with electronic throttle control (ETC) have an adaptive airflow strategy that allows the powertrain control module (PCM) to correct for changes in the airflow. During idle, the PCM monitors the throttle angle and airflow. If the airflow is determined to be less than expected, the PCM adjusts the throttle angle to compensate.

The PCM only learns the adaptive airflow when the vehicle is at idle and normal operating temperature and the airflow is less than a calibrated limit. Whenever the battery is disconnected or the keep alive memory (KAM) is reset, it is necessary for the PCM to learn the new value and not use the default value. For additional information on a KAM reset, refer to RESETTING THE KEEP ALIVE MEMORY (KAM) .

Brake Over Accelerator

Note. On some vehicles, for off road use the brake over accelerator feature can be disabled along with the electronic stability control system by pressing and holding the traction control OFF button for 5 seconds (Mustang and Raptor).

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

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

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

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

The check fuel cap indicator is a communications network message sent by the PCM. The PCM sends the message to illuminate the lamp when the strategy determines there is a concern in the EVAP system due to the fuel filler cap or capless fuel tank filler pipe not being sealed correctly. This is detected by the inability to pull vacuum in the fuel tank after a fueling event.

Computer Controlled Shutdown

The PCM controls the PCM power relay when the ignition is turned to the ON or START position, by grounding the PCM relay control (PCMRC) circuit. After the ignition 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 ignition 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, allows for increased rear heated oxygen sensor (HO2S) concern detection, and allows for misfire profile correction learning.

Engine RPM Limiter

The PCM disables some or all of the fuel injectors whenever an engine RPM over speed condition is detected. The purpose of the engine RPM limiter is to prevent damage to the powertrain. Once the driver reduces the excessive engine speed, the engine returns to the normal operating mode. No repair is required. However, the technician should clear the diagnostic trouble codes (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

Note. Not all vehicles with a cylinder head temperature (CHT) sensor have the fail-safe cooling strategy.

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

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

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

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

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

Failure Mode Effects Management (FMEM)

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

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 through the data link connector (DLC) without removing the PCM from the vehicle.

Fuel Level Input (FLI)

The FLI is a communications network message. Most vehicle applications use a potentiometer type FLI sensor connected to a float in the fuel pump (FP) assembly to determine fuel level.

Short Term Fuel Trim

If the oxygen sensors are warmed up and the PCM determines the engine can operate near stoichiometric air to fuel ratio (14.7:1 for gasoline), the PCM enters closed loop fuel control mode. Since an oxygen sensor can only indicate rich or lean, the fuel control strategy continuously adjusts the desired air to fuel ratio between rich and lean causing the oxygen sensor to switch around the stoichiometric point. If the time between rich and lean switches are the same, then the system is actually operating at stoichiometric. The desired air to fuel control parameter is called short term fuel trim (SHRTFT1 and 2) 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 between -25% and 25%. Some calibrations have time between switches and short term fuel trim excursions that are not equal. These unequal excursions 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 nitrogen oxides (NO x ).

Values for SHRTFT1 and 2 may change significantly on a scan tool as the engine is operated at different RPM and load points. This is because SHRTFT1 and 2 react to fuel delivery variability that changes 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 control, the short term fuel trim corrections are learned by the PCM as long term fuel trim (LONGFT1 and 2) corrections. These corrections are stored in the keep alive memory (KAM) fuel trim tables. Fuel trim tables are based on engine speed and load and by bank for engines with 2 heated oxygen sensor (HO2S) forward of the catalyst. 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 while in open loop and closed loop modes.

Long term fuel trim is represented as a percentage, similar to the short term fuel trim, however it is not a single parameter. A separate long term fuel trim value is used for each RPM and load point of engine operation. Long term fuel trim corrections may change depending on the operating conditions of the engine (RPM and load), ambient air temperature, and fuel quality (% alcohol, oxygenates). When viewing the LONGFT1/2 PID(s), the values may change a great deal as the engine is operated at different RPM and load points. The LONGFT1/2 PID(s) display the long term fuel trim correction currently being used at that RPM and load point.

High Speed Controller Area Network (CAN)

The CAN 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 2 or more electronic modules or nodes to communicate with each other. This communication or multiplexing network operates at 500 kB/sec (kilobytes per second) and allows the electronic modules to share their information messages.

Included in these messages is diagnostic data that is output over the CAN (+) and CAN (-) lines to the DLC. The PCM connection to the DLC is typically done with a 2-wire, twisted pair cable used for the network interconnection. The diagnostic data such as self-test or PIDs can be accessed with a scan tool. For additional information on scan tool equipment, refer to DIAGNOSTIC METHODS .

Idle Air Trim

Idle air trim is designed to adjust the idle air control calibration to correct for wear and aging of components. When the engine conditions meet the learning requirement, the strategy monitors the engine and determines the values required for ideal idle calibration. The idle air trim values are stored in a table for reference. This table is used by the PCM as a correction factor when controlling the idle speed. The table is stored in the KAM and retains the learned values even after the engine is shut OFF. A DTC is set if the idle air trim has reached its learning limits.

Whenever an idle air control component is replaced, or a repair affecting idle is carried out, it is recommended the KAM be reset. This is necessary so the idle strategy does not use the previously learned idle air trim values.

To reset the KAM, refer to RESETTING THE KEEP ALIVE MEMORY (KAM) . It is important to note that erasing DTCs with a scan tool does not reset the idle air trim table.

Once the KAM has been reset, the engine must idle for 15 minutes (actual time varies between strategies) to learn new idle air trim values. Idle quality improves as the strategy adapts. Adaptation occurs in 4 separate modes as shown in the following table.

IDLE AIR TRIM LEARNING MODES CHART

Failure Type Byte

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

For example, P0110:1C-AF means intake air temperature (IAT) sensor circuit voltage out of range. The base DTC, P0110, means IAT 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 2 byte DTCs for generic scan tool communications. Additionally, the OBD II regulations require the 2 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 8 bits in the status byte has a precise meaning that is defined in ISO 14229.

The protocol is that bit 7 is the most significant and left most bit, while bit 0 is the least significant and right most bit.

Multiplexing

The increased number of modules on the vehicle necessitates a more efficient method of communication. Multiplexing is a method of sending 2 or more signals simultaneously over a single circuit. In an automotive application, multiplexing is used to allow 2 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, 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

Currently Ford Motor Company uses CAN communication language protocol to communicate with the PCM.

For additional information about the module communications network, refer to the appropriate Module Communications Network article for Description and Operation.

Vehicle Speed Limiter

The PCM disables some or all of the fuel injectors whenever a vehicle over speed condition is detected. The purpose of the vehicle speed limiter is to prevent damage to the powertrain. Once the driver reduces the excessive vehicle speed, 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.

Either excessive wheel slippage caused by sand, gravel, rain, mud, snow, ice or excessive RPM increase in neutral may cause the vehicle speed limiter to activate even though the vehicle has not exceeded the maximum speed limit.

Powertrain Control Module - Vehicle Speed Output (PCM-VSO)

The PCM-VSO speed signal subsystem generates vehicle speed information for distribution to modules and subsystems that require vehicle speed data. This subsystem senses the transmission output shaft speed with a sensor. The data is processed by the PCM and distributed as a message on the vehicle communication network.

The key features of the PCM-VSO system are to

1. infer vehicle movement from a speed sensor.
2. convert transmission output shaft rotational information to vehicle speed information.
3. compensate for tire size and axle ratio with a programmed calibration variable.
4. distribute vehicle speed information as a multiplexed message.

The signal from a non-contact shaft sensor, such as an OSS or VSS, mounted on the transmission is sensed directly by the PCM. The PCM converts the OSS or VSS information to 8, 000 pulses per mile, based on a tire and axle ratio conversion factor. This conversion factor is programmed into the PCM at the time the vehicle is assembled and can be reprogrammed in the field for changes in the tire size and axle ratio. The PCM transmits the computed vehicle speed and distance traveled information to all vehicle speed signal users on the vehicle.

Malfunction Indicator Lamp (MIL)

The MIL notifies the driver 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) sets.

Scheme 77

1. The MIL is located in the instrument cluster (IC) or instrument panel cluster (IPC) and is labeled CHECK ENGINE, SERVICE ENGINE SOON or the international standards organization (ISO) standard engine symbol.
2. The MIL is illuminated during the IC (IPC) prove out for approximately 4 seconds.
3. The MIL remains illuminated after IC (IPC) prove out if: an emission-related concern and DTC exists. the PCM does not send a control message to the IC (IPC) (applications with the MIL controlled through the communication link).
4. The MIL remains OFF during the IC (IPC) prove out if an indicator or IC (IPC) concern is present.
5. To turn OFF the MIL after a repair, a reset command from the scan tool must be sent, or 3 consecutive drive cycles must be completed without a concern.
6. For all MIL concerns, go to «SYMPTOM CHARTS»(ref-477696) article .
7. If the MIL flashes at a steady rate, a severe misfire condition may exist.
8. If the MIL flashes erratically, the PCM can reset while cranking if the battery voltage is low.
9. The MIL flashes after a period of time with the ignition ON engine OFF, unless the OBD inspection/maintenance (I/M) readiness indicators indicate all of the OBD monitors have completed since the last keep alive memory (KAM) reset or since the PCM DTCs have been cleared.

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 catalytic converter assists in controlling the concentration of exhaust gas products released to the atmosphere. 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 between 246°C - 302°C (475°F - 575°F). A light off catalyst is a three way catalytic converter (TWC) that is located as close to the exhaust manifold as possible. Because the light off catalyst is located close to the exhaust manifold it achieves the required temperature faster and reduces emissions more quickly than the catalyst located under the body. Once the catalyst lights off, it quickly reaches the maximum conversion efficiency for that catalyst.

Three Way Catalytic Converter (TWC) Conversion Efficiency

A TWC requires a stoichiometric air fuel ratio of 14.7 pounds of air to 1 pound of gasoline, or 14.7:1, for high conversion efficiency. In order to achieve these high efficiencies, the air to fuel ratio must be tightly controlled with a narrow window of stoichiometry. Deviations outside of this window greatly decrease the conversion efficiency. For example a rich mixture decreases the HC and CO conversion efficiency while a lean mixture decreases the NO x conversion efficiency.

For vehicles using E85 the required air to fuel ratio is 9.8:1. Other gasoline/ethanol mixtures require a variable air to fuel ratio between 14.7:1 to 9.8:1 dependent on the percentage of ethanol content.

Scheme 78

Exhaust System

The exhaust system conveys 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.

Scheme 79

Underbody Catalyst

The underbody catalyst is located after the light off catalyst. The underbody catalyst may be in line with the light off catalyst, or the underbody catalyst may be common to 2 light off catalysts, forming a Y pipe configuration. For an exact configuration of the catalyst and exhaust system for a specific vehicle, refer to the appropriate Exhaust System article for the exhaust system exploded view.

Three Way Catalytic (TWC) Converter

The TWC converter contains either platinum (Pt) and rhodium (Rh) or palladium (Pd) and rhodium (Rh). The TWC converter catalyzes the oxidation reactions of unburned HCs and CO and the reduction reaction of NO x . The 3-way conversion can be best accomplished by always operating the engine air fuel ratio at or close to stoichiometry.

Exhaust Manifold Runners

The exhaust manifold runners collect exhaust gases from engine cylinders. The number of exhaust manifolds and exhaust manifold runners depends on the engine configuration and number of cylinders.

Exhaust Pipes

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

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

Muffler

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

Enhanced Evaporative Emission (EVAP) Natural Vacuum Leak Detection (NVLD) System - Fiesta

The enhanced EVAP NVLD system consists of the capless fuel tank filler pipe, EVAP canister, normally closed EVAP purge valve, fuel tank, fuel tank mounted vapor control valve, fuel vapor hoses, fuel vapor vent valve, intake manifold hose assembly, the NVLD module, and powertrain control module (PCM). The PCM and the NVLD module check the entire EVAP system, including all the fuel vapor hoses from the NVLD module to the intake manifold, for a leak when the calibrated conditions are met. For additional information on the EVAP system components, refer to ENGINE CONTROL COMPONENTS .

Scheme 80

1. The PCM uses inputs from the engine coolant temperature (ECT) sensor, the fuel level input (FLI), the intake air temperature (IAT) sensor, the mass airflow (MAF) sensor, the NVLD ambient air temperature sensor, the vehicle speed sensor (VSS) and the NVLD module to determine conditions of the enhanced EVAP system. The PCM uses the combination of these signals to determine when to activate the EVAP leak check monitors.
2. The PCM uses inputs from the fuel level input (FLI), the NVLD ambient air temperature sensor, and the EVAP canister load to determine 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 purge valve. The PCM uses the enhanced EVAP system inputs to evacuate the system using the EVAP purge valve.
3. The PCM outputs a duty cycle between 0% and 100% to control the EVAP purge valve.
4. The NVLD module vacuum switch and the NVLD relief valves seal the enhanced EVAP system from the atmosphere during the EVAP leak check monitors.
5. A valve inside the fuel vapor tube assembly prevents liquid fuel from entering the EVAP canister and the EVAP purge valve under any vehicle altitude, handling, or rollover condition.

Enhanced Evaporative Emission (EVAP) System - All Others

The enhanced EVAP system consists of a fuel tank, fuel filler cap or capless fuel tank filler pipe, fuel tank mounted or inline fuel vapor control valve, fuel vapor vent valve, EVAP canister, fuel tank mounted or fuel pump mounted or inline fuel tank pressure (FTP) sensor, EVAP purge valve, EVAP check valve (turbocharged engines only), intake manifold hose assembly, EVAP canister vent valve, PCM and connecting wires, and fuel vapor hoses. The enhanced EVAP system, including all the fuel vapor hoses, can be checked when a leak is detected by the PCM. For additional information on the EVAP system components, refer to ENGINE CONTROL COMPONENTS .

Scheme 81

1. The enhanced EVAP system uses inputs from the ECT sensor or cylinder head temperature (CHT) sensor, the IAT sensor, the MAF sensor, the VSS and the FTP sensor to provide information about engine operating conditions to the PCM. The PCM uses the FLI and FTP sensor signals 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 purge valve. The PCM uses the enhanced EVAP system inputs to evacuate the system using the EVAP purge valve, seal the enhanced EVAP system from the atmosphere using the EVAP canister vent valve, and uses the FTP sensor to observe total vacuum lost for a period of time.
3. The EVAP canister vent valve seals the enhanced EVAP system to atmosphere during the EVAP leak check monitor.
4. For Flex 3.5L 4V, Fusion 3.5L, MKS 3.7L, MKT 3.7L, MKZ 3.5L, Taurus 3.5L 4V and Transit Connect the PCM outputs a variable current between 0 and 1, 000 mA to control the EVAP purge valve. For all others, the PCM outputs a duty cycle between 0% and 100% to control the EVAP 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 purge valve under any vehicle altitude, handling, or rollover condition.
7. On turbocharged engines, the EVAP check valve prevents boost pressure from entering the EVAP system.
8. On turbocharged engines, the turbocharger creates boost pressure in the intake manifold.
9. On turbocharged engines, an EVAP ejector (if equipped) is used to create a vacuum in the purge line during boost conditions. When in boost conditions a percentage of the boost pressure is applied to the EVAP ejector to create a vacuum. This vacuum draws purge vapors through the EVAP ejector into the intake air system upstream of the turbocharger.

Highlights Of The EEGR System

1. The EEGR valve is activated by an electric stepper motor.
2. Engine coolant is routed through the assembly on some vehicle applications. Some vehicle applications are air cooled.

Electronic Returnless Fuel System (ERFS)

Note. ERFS vehicles can use either a fuel pump driver module (FPDM) or a fuel pump control module.

The ERFS consists of a fuel tank with reservoir, the fuel pump, the fuel rail pressure temperature (FRPT) sensor, the fuel filter, the fuel supply line, the fuel rail, and the fuel injectors. For additional information on the fuel system components, refer to ENGINE CONTROL COMPONENTS . Operation of the system is as follows

Scheme 82

1. The fuel delivery system is enabled during ignition ON, engine OFF for 1 second (or until fuel rail pressure exceeds target) and during crank (if fuel rail pressure falls below target) or running mode once the PCM receives a crankshaft position (CKP) sensor signal. Commanded rail pressure is a function of fuel rail and engine coolant temperature, with different values commanded during crank vs. normal running.
2. The fuel pump logic is defined in the fuel system control strategy and executed by the PCM.
3. The PCM commands a duty cycle to the FPDM or fuel pump control module.
4. The FPDM or fuel pump control module modulates the voltage to the fuel pump (FP) required to achieve the correct fuel pressure. Voltage for the fuel pump is supplied by the power relay, FPDM power supply relay, or fuel pump control module relay. For additional information, refer to «FUEL PUMP CONTROL - ERFS»(ref-477699-S01146685582012060700000) and «FUEL PUMP MONITOR (FPM) - ERFS»(ref-477699-S18626867712012060700000) .
5. The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail. The PCM uses this information to vary the duty cycle output to the FPDM or fuel pump control module, which changes the fuel pressure to compensate for varying loads and to avoid fuel system vaporization.
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 either the PCM power relay or the fuel pump relay. The ground signal is controlled by the PCM.
7. There are 3 filtering or screening devices in the fuel delivery system. The intake filter is a fine, nylon mesh screen mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. The fuel filter assembly is located between the fuel pump and the fuel rail.
8. The FP assembly is a device that contains the fuel pump and the fuel sender assembly. The fuel pump is located inside the reservoir and supplies fuel through the fuel pump assembly manifold to the engine and the fuel pump assembly jet pump.
9. For vehicles with an inertia fuel shutoff (IFS) switch, the IFS switch de-energizes the fuel delivery secondary circuit in the event of a collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision. For vehicles without an IFS switch, the fuel pump control module receives an event notification signal from the restraints control module (RCM) to disable the fuel pump in the event of a collision. The signal is sent on a dedicated circuit between the fuel pump control module and RCM.

Scheme 83

Fuel Pump Control - ERFS

Note. The Mustang 5.4L uses 2 fuel pump control modules to control fuel for the fuel delivery system. The PCM sends one FP duty cycle on the fuel pump control (FPC) circuit. Both fuel pump control modules use this circuit.

The FP signal is a duty cycle command sent from the PCM to the FPDM or fuel pump control module. The FPDM or fuel pump control module uses the FP command to operate the fuel pump at the speed requested by the PCM or to turn the pump OFF. When the ignition is turned ON, the electric 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 (EDGE 2.0L, EXPLORER 2.0L, FOCUS)

FUEL PUMP DUTY CYCLE OUTPUT FROM PCM (MUSTANG 5.4L)

FUEL PUMP DUTY CYCLE OUTPUT FROM PCM (ALL OTHERS)

For additional information, refer to POWERTRAIN CONTROL HARDWARE , FUEL PUMP DRIVER MODULE (FPDM) or FUEL PUMP CONTROL MODULE .

Fuel Pump Monitor (FPM) - ERFS

Note. The Mustang 5.4L uses 2 fuel pump control modules to control fuel for the fuel delivery system. The PCM individually monitors both fuel pump control modules through the FPM and FPM2 circuits.

The FPDM or fuel pump control module communicates diagnostic information to the PCM through the FPM circuit. This information is sent by the FPDM or fuel pump control module as a duty cycle signal. The 3 duty cycle signals that may be sent are listed in the following table.

FUEL PUMP CONTROL MODULE DUTY CYCLE SIGNALS (EDGE 2.0L, EXPLORER 2.0L, FOCUS AND MUSTANG 5.4L)

FUEL PUMP DRIVER MODULE DUTY CYCLE SIGNALS (ALL OTHERS)

For additional information, refer to POWERTRAIN CONTROL HARDWARE , FUEL PUMP DRIVER MODULE (FPDM) or FUEL PUMP CONTROL MODULE .

Mechanical Returnless Fuel System (MRFS) - Single Speed

Note. The MRFS can be configured with a single or dual speed fuel pump. The dual speed MRFS incorporates a fuel pump control module which is used to control the speed of the fuel pump. For additional information on the fuel pump control module, refer to POWERTRAIN CONTROL HARDWARE .

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

Scheme 84

1. The fuel delivery system is enabled during ignition ON, engine OFF for 1 second and during crank or running mode once the PCM receives a CKP sensor signal.
2. The fuel pump logic is defined in the fuel system control strategy and is carried out by the PCM.
3. The PCM grounds the fuel pump relay, which provides power to the fuel pump.
4. The IFS switch de-energizes the fuel delivery secondary circuit in the event of collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision.
5. A pressure test point valve, Schrader valve, is located on the fuel rail and measures the fuel injector supply pressure for diagnostic procedures and repairs. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit 134-R0087 or equivalent.
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 either the PCM power relay or the fuel pump relay. The ground signal is controlled by the PCM.
7. There are 3 to 5 filtering or screening devices in the fuel delivery system. For additional information refer to «FUEL FILTERS»(ref-477699-S29523531692012060700000) .
8. The FP assembly contains the fuel pump, the fuel pressure regulator, and the fuel sender assembly. The fuel pressure regulator is attached to the FP assembly 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 assembly is located in the fuel tank.

Fuel Pump Control - Single Speed MRFS

The output signal from the PCM controls the electric fuel pump. With the PCM power relay contacts closed, vehicle power (VPWR) is sent to the coil of the fuel pump relay. For electric fuel pump operation, the PCM grounds the FP circuit, which is connected to the coil of the fuel pump relay. This energizes the coil and closes the contacts of the relay, sending B+ through the FP PWR circuit to the electric fuel pump. When the ignition is turned ON, the electric fuel pump runs for about 1 second and is turned OFF by the PCM if engine rotation is not detected.

Fuel Pump Monitor (FPM) - Single Speed MRFS

The FPM circuit is spliced into the fuel pump power (FP PWR) circuit and is used by the PCM for diagnostic purposes. The PCM sources a low current voltage down the FPM circuit. With the fuel pump OFF, this voltage is pulled low by the path to ground through the fuel pump. With the fuel pump OFF and the FPM circuit low, the PCM can verify the FPM and FP PWR circuits are complete from the FPM splice through the fuel pump to ground. This also confirms that the FP PWR or FPM circuits are not short to power. With the fuel pump ON, voltage is now being supplied from the fuel pump relay to the FP PWR and FPM circuits. With the fuel pump ON and the FPM circuit high, the PCM can verify the FP PWR circuit from the fuel pump relay to the FPM splice is complete. It can also verify the fuel pump relay contacts are closed and there is a B+ supply to the fuel pump relay.

Mechanical Returnless Fuel System (MRFS) - Dual Speed

Note. The MRFS can be configured with a single or dual speed fuel pump. The dual speed MRFS incorporates a fuel pump control module which is used to control the speed of the fuel pump. For additional information, refer to POWERTRAIN CONTROL HARDWARE .

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, fuel injectors, and a Schrader valve/pressure test point (if equipped).

For vehicles with gasoline direct fuel injection, a pressure accumulator is incorporated into the fuel line to prevent fuel vapor formation after several hours of cold soak and reduce crank time.

For additional information on the fuel system components, refer to ENGINE CONTROL COMPONENTS . Operation of the system is as follows

Scheme 85

1. The fuel delivery system is enabled during ignition ON, engine OFF for 1 second and during crank or running mode once the PCM receives a CKP sensor signal. On vehicles with gasoline direct fuel injection, the high pressure fuel system may be under vacuum after several hours of cold soak. Fuel vapor may collect at the fuel injection pump, causing a long start condition. To prevent this, the fuel pump relay is energized for 1 or 2 seconds, depending on application, as soon as the dome light is commanded ON. This causes the fuel pump control module and the fuel pump to cycle for 1 or 2 seconds and purge any trapped air or fuel vapor from the high pressure fuel system.
2. The fuel pump logic is defined in the fuel system control strategy and executed by the PCM.
3. For vehicles with an IFS switch, the switch disables the voltage to the fuel pump control module in the event of a collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision. For vehicles without an IFS switch, the fuel pump control module receives an event notification signal from the RCM to disable the fuel pump in the event of a collision. The signal is sent on a dedicated circuit between the fuel pump control module and RCM.
4. The PCM commands a duty cycle to the fuel pump control module. The fuel pump control module reports diagnostic information to the PCM.
5. The fuel pump control module controls the voltage to the fuel pump (FP) based on the duty cycle request from the PCM. Voltage for the fuel pump is supplied by the fuel pump control module relay. For additional information refer to «FUEL PUMP CONTROL - DUAL SPEED MRFS»(ref-477699-S28317511272012060700000) and «FUEL PUMP MONITOR (FPM) - DUAL SPEED MRFS»(ref-477699-S39265032252012060700000) .
6. A pressure test point valve (Schrader valve) is located on the fuel rail and measures the fuel injector supply pressure for diagnostic procedures and repairs. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit 134-R0087 or equivalent.
7. 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.
8. There are 3 to 5 filtering or screening devices in the fuel delivery system. For additional information, refer to «FUEL FILTERS»(ref-477699-S29523531692012060700000) .
9. The FP assembly contains the fuel pump, the fuel pressure regulator, lifetime fuel filter (if equipped) and the fuel sender assembly. The fuel pressure regulator is attached to the FP assembly 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 assembly is located in the fuel tank.

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 ignition is turned ON, the fuel pump runs for about 1 second and is requested OFF by the PCM if engine rotation is not detected.

FUEL PUMP DUTY CYCLE OUTPUT FROM PCM

Fuel Pump Monitor (FPM) - Dual Speed MRFS

The fuel pump control module communicates diagnostic information to the PCM through the FPM circuit. This information is sent by the fuel pump control module as a duty cycle signal. The 4 duty cycle signals that may be sent are listed in the following table.

Note. The Expedition and Navigator have the event notification signal circuit and an IFS switch. The event notification signal information is calibrated off in the PCM and the IFS switch disables the voltage to the fuel pump control module in the event of a collision. Some vehicles use a fuel pump control module relay located in the body control module (BCM) that is disabled when the BCM detects a crash event. These vehicles do not use an IFS switch nor an event notification signal circuit.

FUEL PUMP CONTROL MODULE DUTY CYCLE SIGNALS

Fuel Filters

The system contains 3 to 5 filtering or screening devices. Refer to appropriate Fuel Tank and Lines article, for the individual component locations.

1. The fuel intake filter or screen is a fine nylon mesh filter mounted on the intake side of the fuel pump. It is part of the assembly and cannot be repaired separately.
2. The filter/screen at the fuel rail port of the injectors is part of the fuel injector assembly and cannot be repaired separately.
3. The filter/screen at fuel inlet side of the fuel pressure regulator is part of the regulator assembly and cannot be repaired separately.
4. The fuel filter assembly is located between the fuel pump and the pressure test point (Schrader valve) or injectors. This filter may be a lifetime fuel filter located in the fuel pump assembly or an external 3- port inline filter that allows clean fuel to return to the fuel tank. A new filter may be installed for the external filter.
5. The fuel filter sock is located on the fuel pump assembly between the reservoir and the fuel tank.

On some gasoline direct fuel injection applications, there is a fuel pressure sensor located in the fuel line that allows the PCM to monitor the low pressure fuel system operation. For additional information, refer to ENGINE CONTROL COMPONENTS , FUEL PRESSURE SENSOR .

Integrated Electronic Ignition System

Note. Electronic ignition engine timing is controlled entirely by the PCM. Electronic ignition engine timing is not adjustable. Do not attempt to check base timing. You will receive false readings.

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

Scheme 86

Scheme 87

1. The CKP sensor indicates the 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 electronic ignition system to identify the compression stroke of cylinder 1 and to synchronize the firing of the individual coils.
2. The PCM uses the CKP sensor signal to calculate a spark target and then fires the coil pack(s) to that target shown. The PCM uses the CMP sensor signal to identify the compression stroke of cylinder 1, and to synchronize the firing of the individual coils.
3. The PCM controls the ignition coils after it calculates the spark target. The COP system fires only one spark plug per coil upon synchronization during the compression stroke. For the coil pack ignition system, each coil within a pack fires 2 spark plugs at the same time. The plugs are paired so that as one fires during the compression stroke the other fires during the exhaust stroke. The next time the coil is fired the situation is reversed. The current flow, or dwell, through the primary ignition coil is controlled by the PCM by providing a switched ground path through the ignition coil driver to ground. When the ignition coil driver is switched ON, current rapidly builds up to a maximum value, determined by the coil inductance and resistance. When the current is switched OFF, the magnetic field collapses which induces a secondary high voltage surge and the spark plug is fired. This high voltage surge creates a flyback voltage which the PCM uses as a feedback during the ignition diagnostics. The PCM uses the charge current dwell time characteristics to carry out the ignition diagnostics.
4. The PCM processes the CKP sensor signal and uses it to drive the tachometer as the clean tach output (CTO) signal.

Engine Crank/Engine Running

During engine crank the PCM fires 2 spark plugs simultaneously. Of the 2 spark plugs fired, one is under compression while the other is on the exhaust stroke. Both spark plugs fire until camshaft position is identified by a successful CMP sensor signal. Once camshaft position is identified only the cylinder under compression is fired.

Camshaft Position Failure Mode Effects Management (FMEM)

During camshaft position 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.

Heated Fittings or Tube

1. non-heated
2. water heated
3. with PCM-controlled heating element

PCV Valves

1. non-heated
2. with PCM-controlled heating element

Refer to the following figures for examples of these types of PCV valves.

Scheme 88

Scheme 89

Scheme 90

Supercharger Bypass (SCB) System

The SCB system allows the high pressure air at the outlet of the supercharger to vent back into the inlet of the supercharger, equalizing the pressure. This eliminates the boost (increased pressure that the supercharger produces) for times when supercharger function is undesirable. The system uses a vacuum bypass actuator, which controls the bypass valve inside the supercharger. The system normally operates with engine vacuum applied to the upper port of the vacuum bypass actuator, while the lower port references the air pressure in the clean air tube to cancel out any pressure difference in the intake air system. The actuator is set to open (bypassing the supercharger) during high vacuum engine conditions. As the throttle is opened and engine vacuum decreases, the actuator closes to allow the supercharger to pressurize the air in the manifold.

Charge Air Cooler (CAC) System

The CAC system cools the intake air which has been heated by the supercharger. The removal of heat from the pressurized air going into the CAC increases the air density which improves combustion efficiency, engine horsepower, and torque. The system consists of an additional CAC radiator in the grille, a reservoir (independent from the engine cooling system), an electric water pump, the CAC located in the lower intake manifold, and tubing to interconnect these components. The CAC is positioned after the supercharger directly in the flow of the intake air. As the heated air flows through the CAC, heat is transferred to the coolant which is circulated back to the CAC radiator to be cooled by the airflow through the grille. The CAC pump is controlled by the powertrain control module (PCM). The PCM maintains a desirable intake air temperature by monitoring a second intake air temperature (IAT2) sensor in the lower intake manifold.

Scheme 91

Scheme 92

Scheme 93

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 2 wires).
2. There are 2 designs: parallel and inline. The parallel design has the motor under the bore parallel to the plate shaft. The motor housing is integrated into the main housing. The inline design has a separate motor housing.
3. An internal spring is used in both designs 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.
4. The closed throttle plate hard stop prevents the throttle from binding in the bore. This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle.
5. 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.
6. 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 2 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 TP 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.

Depending on the application either a 2 track or 3 track APP sensor is used. 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 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 fuel control and transmission shift schedules while delivering the requested wheel torque.

The ETC monitor system is distributed across 2 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 checker 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 WITH 3 TRACK APP SENSOR FAILURE MODE EFFECTS MANAGEMENT

ETC SYSTEM WITH 2 TRACK APP SENSOR FAILURE MODE AND EFFECTS MANAGEMENT

ELECTRONIC THROTTLE MONITOR OPERATION

APP And TP Sensor Inputs

ACCELERATOR PEDAL POSITION (APP) SENSOR CHECK

THROTTLE POSITION (TP) SENSOR CHECK

Electronic Throttle Actuator Control (TAC) Output

ELECTRONIC TAC OPERATION CHECK

Turbocharger System

A turbocharger is an exhaust gas driven device used to increase the power output of an engine by increasing the mass of air entering the engine. The increased mass of air is achieved by the compressor increasing the pressure of the air entering the engine. Compressing the air causes the temperature to increase. The temperature increase is counteracted using a charge air cooler to increase the density of the air prior to induction into the cylinder. The turbocharger uses exhaust gas energy to drive the radial compressor.

The 6 cylinder engine uses twin turbochargers in a parallel arrangement with one turbine connected to the exhaust of each cylinder bank. This configuration improves engine responsiveness due to the reduced inertia of 2 small rotating assemblies in the place of a single large one while pumping adequate air to achieve the rated power. Emission compliance is achieved by mounting the catalysts very close to the turbo outlet.

The engine control system manages bypass valves for both the compressor and turbine stages. Two bypass valves are used to bypass the compressors on heavy throttle releases to prevent an unwanted air rush noise from the turbocharger. The bypass valves provide a connection between the high pressure and low pressure sides of the compressor. The wastegate on the turbine side is opened to reduce exhaust gas flow through the turbine when boost is not needed. A pneumatic actuator changes the wastegate valve opening. The wastegate is controlled by the powertrain control module (PCM) through a pulse width modulated (PWM) turbocharger wastegate regulating valve solenoid. The turbocharger wastegate regulating valve solenoid then regulates the supplying pressure to the wastegate canister to open the poppet style wastegate valve. The wastegate may be pressure or vacuum actuated, and the poppet style wastegate valve could be normally opened or normally closed at idle or low engine airflow conditions depending on vehicle configuration and requirements such as fuel economy and boost performance. The wastegates are coupled by having one control output from the turbocharger wastegate regulating valve solenoid that drives both turbocharger wastegate actuators.

The 4 cylinder system is similar, but uses only one turbocharger, wastegate and bypass valve instead of two. The compressor bypass valve can be electric or pneumatic and it may be mounted in the air induction system or in the compressor cover.

Scheme 94

Scheme 95

The CAC system cools the intake air which has been heated by the turbocharger. The removal of heat from the pressurized air going into the CAC increases the air density which improves combustion efficiency, engine horsepower, and torque. The system consists of a CAC radiator in the grille and tubing to interconnect these components. The CAC is positioned after the turbocharger directly in the flow of the intake air. As the heated air flows through the CAC, it is cooled by the airflow through the grille. The PCM maintains a desirable intake air temperature by monitoring the TCBP/CACT (located at the throttle body) and the MAP/IAT2 (located at the intake manifold) sensors.

Scheme 96

Scheme 97

VCT System

The VCT system consists of an electric hydraulic positioning control solenoid, a camshaft position (CMP) sensor, and a trigger wheel. The CMP sensor 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.

Scheme 98

1. The PCM receives input signals from the intake air temperature (IAT), engine coolant temperature (ECT), CMP, throttle position (TP), mass airflow (MAF), and CKP sensors to determine the operating conditions of the engine. At idle and low engine speeds with closed throttle, the PCM controls the camshaft position based on engine coolant temperature, engine oil temperature, intake air temperature, and mass airflow. During part and wide open throttle, the camshaft position is determined by engine RPM, load and throttle position. The VCT system does not operate until the engine is at normal operating temperature.
2. The VCT system is enabled by the PCM when the correct conditions are met.
3. The CKP signal is used as a reference for 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. The PCM calculates and determines the desired camshaft position. It continually updates the VCT solenoid duty cycle until the desired position is achieved. A difference between the desired and actual camshaft position represents a position error in the PCM VCT control loop. The PCM disables the VCT and places the camshaft in a default position if a concern is detected. A related DTC also sets when the concern is detected.
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 2 halves couple the camshaft to the timing chain. When the flow of oil is shifted from one side of the chamber to the other, the differential change in oil pressure forces the camshaft to rotate in either an advance or retard position depending on the oil flow.

OBD I Systems

OBD I vehicles use the same PCM, controller area network (CAN) serial data communication link, J1962 Data Link Connector, and PCM software as the corresponding OBD II vehicle. The only difference is the possible removal of the rear oxygen sensor(s), fuel tank pressure (FTP) sensor, EVAP canister vent valve, and a different PCM calibration. Starting in the 2006 model year, all Federal vehicles from 8, 500 to 14, 000 lbs. Gross Vehicle Weight Rating (GVWR) will have been phased into OBD II and OBD I systems will no longer be utilized in vehicles up to 14, 000 lbs. GVWR.

OBD II Systems

The OBD II system monitors virtually all emission control systems and components that can affect tailpipe or evaporative emissions. In most cases, concerns must be detected before emissions exceed 1.5 times the applicable 120, 000 or 150, 000 mile emission standards. Partial zero emission vehicles (PZEV) and super ultra low emission vehicles (SULEV-II) can use 2.5 times the standard in place of the 1.5 times the standard. If a system or component exceeds emission thresholds or does not operate within a manufacturer's specifications, a DTC is stored and the MIL is illuminated within 2 drive cycles.

The OBD II system monitors for concerns either continuously (regardless of driving mode) or non-continuously (once per drive cycle during specific drive modes). A pending DTC is stored in the PCM keep alive memory (KAM) when a concern is initially detected. Pending DTCs are displayed as long as the concern is present. OBD regulations require a complete concern free monitoring cycle to occur before erasing a pending DTC. This means that a pending DTC is erased on the next power up after a concern free monitoring cycle. However, if the concern is still present after 2 consecutive drive cycles, the MIL is illuminated. Once the MIL is illuminated, 3 consecutive drive cycles without a concern being detected are required to extinguish the MIL. The DTC is erased after 40 engine warm-up cycles once the MIL is extinguished.

In addition to specifying and standardizing much of the diagnostics and MIL operation, OBD requires the use of a standard data link connector (DLC), standard communication links and messages, standardized DTCs and terminology. Examples of standard diagnostic information are freeze frame data and inspection/maintenance (I/M) readiness indicators.

Freeze frame data describes data stored in KAM at the point the concern is initially detected and the pending DTC is stored. Freeze frame data consists of parameters such as engine RPM, engine load, vehicle speed or throttle position. Freeze frame data is updated when the concern is detected again on a subsequent drive cycle and a confirmed DTC is stored; however, a previously stored freeze frame is overwritten if a higher priority fuel or misfire concern is detected. This data is accessible with the scan tool to allow duplicating the conditions when the concern occurred in order to assist in repairing the vehicle.

OBD I/M readiness indicators show whether all of the OBD monitors have been completed since the last time the KAM or the PCM DTC(s) have been cleared. Ford vehicles blink the MIL after 15 seconds of ignition ON engine OFF time to indicate that some monitors have not completed. In some states, it may be necessary to carry out an OBD check in order to renew a vehicle registration. The I/M readiness indicators must show that all monitors have been completed prior to the OBD check.

Starting in the 1996 model year, OBD II was required on all California and California State gasoline engine vehicles up to 14, 000 lbs. GVWR. Starting in the 1997 model year, diesel engine vehicles up to 14, 000 lbs. GVWR required OBD II.

California states are ones that have adopted California emission regulations, starting in the 1998 model year. For example, Connecticut, Maine, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington have adopted California's emission regulations. These states receive California-certified vehicles for passenger cars, light trucks, and medium-duty vehicles up to 14, 000 lbs GVWR.

Starting in the 1996 model year, OBD II was also required on all Federal gasoline engine vehicles up to 8, 500 lbs. GVWR. Starting in the 1997 model year, diesel engine vehicles up to 8, 500 lbs. GVWR required OBD II.

Starting in the 2004 model year, Federal vehicles over 8, 500 lbs. are required to phase in OBD II. Starting in the 2004 model year, gasoline fueled medium duty passenger vehicles (MDPVs) are required to have OBD II. By the 2006 model year, all Federal vehicles from 8, 500 to 14, 000 lbs. GVWR will have been phased into OBD II.

Heavy Duty (HD) OBD II Systems

Starting in the 2010 model year, California and Federal gasoline fueled and diesel fueled on road heavy duty engines used in vehicles over 14, 000 lbs. GVWR are required to phase into HD OBD II. All vehicles over 14, 000 lbs. GVWR must comply for the 2013 model year. Vehicles that do not comply with HD OBD II during the phase in period must comply with EMD+.

EMD Systems

EMD was required on all 2007 model year and beyond California gasoline and diesel fueled on road heavy duty engines used in vehicles over 14, 000 lbs GVWR. EMD systems are required to functionally monitor the fuel delivery system, exhaust gas recirculation (EGR) system, particulate matter trap, as well as emission related PCM inputs for circuit continuity and rationality, and emission related outputs for circuit continuity and functionality. For gasoline engines which have no particulate matter trap, EMD requirements are very similar to current OBD I system requirements. As such, OBD I system philosophy is employed, the only change being the addition of some comprehensive component monitor (CCM) rationality and functionality checks.

The EMD vehicles use the same PCM, CAN, serial data communication link, J1962 DLC, and PCM software as the corresponding OBD II vehicle. The only difference is the possible removal of the rear oxygen sensor (s), FTP sensor, EVAP canister vent valve (if equipped), and a different PCM calibration.

Starting in the 2010 model year, EMD requires functional monitoring of the NO X after treatment system on gasoline engines. This requirement is commonly known as EMD+.

The following list indicates what monitors and functions have been altered from OBD II for gasoline engine EMD calibrations

The following monitor descriptions provide a general description of each OBD monitor. In these descriptions, the monitor strategy, hardware, testing requirements, and methods are presented to provide an overall understanding of monitor operation. An illustration of each monitor may also be provided. These illustrations should be used as typical examples and are not intended to represent all possible vehicle configurations.

Each illustration depicts the PCM as the main focus with primary inputs and outputs for each monitor. The icons to the left of the PCM represent the inputs used by each of the monitor strategies to enable or activate the monitor. The components and subsystems to the right of the PCM represent the hardware and signals used while carrying out the tests and the systems being tested. The CCM illustration has numerous components and signals involved which are shown generically. When referring to the illustrations, match the numbers to the corresponding numbers in the monitor descriptions for a better understanding of the monitor and associated DTCs.

These icons are used in the illustrations of the OBD monitors and throughout this service information.

Scheme 99

Air Fuel Ratio Imbalance Monitor

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

Scheme 100

Catalyst Efficiency Monitor

The catalyst efficiency monitor uses an oxygen sensor before and 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 sensors are switching. Under normal closed-loop fuel conditions, high efficiency catalysts have significant oxygen storage. This makes the switching frequency of the rear heated oxygen sensor (HO2S) very slow and reduces the amplitude, which provides for a shorter signal length. The front HO2S switches more frequently with greater amplitude, which provides for a longer signal length. As the catalyst efficiency deteriorates due to thermal and chemical deterioration, its ability to store oxygen declines. The post-catalyst or downstream HO2S signal begins to switch more rapidly with increasing amplitude and signal length, approaching the switching frequency, amplitude, and signal length of the pre-catalyst or upstream HO2S. The predominant failure mode for high mileage catalysts is chemical deterioration (phosphorus deposits on the front brick of the catalyst), not thermal deterioration.

For the typical HO2S, the catalyst monitor counts the number of front HO2S switches during part throttle, closed loop fuel conditions after the engine is warmed-up and the inferred catalyst temperature is within limits. The number of front switches are accumulated, depending on the calibration, in up to 3 different air mass regions or cells. While catalyst monitoring entry conditions are being met, the front and rear HO2S signal lengths are continually being calculated. When the required number of front switches has accumulated in each cell, the total signal length of the rear HO2S is divided by the total signal length of the front HO2S to compute a catalyst index ratio. 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.

For the universal HO2S, the catalyst 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. The fixed fuel control routine is the same for every vehicle with universal HO2Ss. During monitor operation the rear HO2S signal lengths are continually calculated. The calculated rear HO2S signal length is then divided by a calibrated signal length, which has compensation for mass airflow. The calibrated signal length is based on the signal length of an HO2S placed after a catalyst without a washcoat. 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.

Inputs from engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), mass airflow (MAF), crankshaft position (CKP), throttle position (TP), and vehicle speed sensors are required to enable the catalyst efficiency monitor.

Typical Monitor Entry Conditions

1. Minimum 330 seconds since start-up at 21°C (70°F)
2. Engine coolant temperature is between 76.6°C - 110°C (170°F - 230°F)
3. Intake air temperature is between -7°C - 82°C (20°F - 180°F)
4. Time since entering closed-loop is 30 seconds
5. Inferred rear HO2S temperature of 482°C (900°F)
6. EGR is between 1% and 12%
7. Part throttle, maximum rate of change is 0.2 volts/0.050 sec
8. Vehicle speed is between 8 and 112 km/h (5 and 70 mph)
9. Fuel level is greater than 15%
10. First Airflow Cell Engine RPM 1, 000 to 1, 300 RPM Engine load 15 to 35% Inferred catalyst temperature 454°C - 649°C (850°F - 1, 200°F) Number of front HO2S switches is 50
11. Second Airflow Cell Engine RPM 1, 200 to 1, 500 RPM Engine load 20 to 35% Inferred catalyst temperature 482°C - 677°C (900°F - 1, 250°F) Number of front HO2S switches is 70
12. Third Airflow Cell Engine RPM 1, 300 to 1, 600 RPM Engine load 20 to 40% Inferred catalyst temperature 510°C - 704°C (950°F - 1, 300°F) Number of front HO2S switches is 30

The diagnostic trouble codes (DTCs) associated with this test are DTC P0420 (Bank 1 or Y-pipe system) and P0430 (Bank 2). Because an exponentially weighted moving average algorithm is used to determine a concern, up to 6 driving cycles may be required to illuminate the malfunction indicator lamp (MIL) during normal customer driving. If the keep alive memory (KAM) is reset or the battery is disconnected, a concern illuminates the MIL in 2 drive cycles.

Vehicles With Universal HO2S

The catalyst monitor duration is 12 seconds, once per drive cycle. If the catalyst monitor conditions are met, the catalyst monitor may run and complete after all of the upstream HO2S functional tests are complete and the EVAP system is functional, with no stored DTCs; however, the catalyst monitor may run and complete before the downstream HO2S deceleration fuel shut off test is complete. In this case, the catalyst monitor inspection maintenance (I/M) readiness flag may indicate complete before the O2S I/M readiness flag indicates complete. If the catalyst monitor does not complete during a particular driving cycle, the already accumulated switch/signal data is retained in the KAM and is used during the next driving cycle to allow the catalyst monitor a better opportunity to complete.

Vehicles With HO2S

The catalyst monitor runs up to 700 seconds, once per drive cycle. If the catalyst monitor conditions are met the catalyst monitor runs but the catalyst monitor IM readiness flag does not indicate complete until the HO2S monitor is complete and the EVAP system is functional with no stored DTCs. If the catalyst monitor does not complete during a particular driving cycle, the already accumulated switch and signal data is retained in the KAM and used during the next driving cycle to allow the catalyst monitor a better opportunity to complete.

Rear HO2S can be located in various configurations to monitor different kinds of exhaust systems. Inline engines and many V engines are monitored by their individual bank. A rear HO2S is used along with the front, fuel control HO2S for each bank. Two sensors are used on an inline engine and 4 sensors are used on a V engine. Some V engines have exhaust banks that combine into a single underbody catalyst. These systems are referred to as Y pipe systems. They use only one rear HO2S along with the 2 front, fuel-control HO2S. The Y pipe system uses 3 sensors in all. For Y piped systems, the 2 front HO2S signals are combined by the PCM software to infer what the HO2S signal would have been in front of the monitored catalyst. The inferred front HO2S signal and the actual single, rear HO2S signal is then used to calculate the index ratio.

Exhaust systems that use an underbody catalyst without a downstream/rear HO2S are not monitored by the catalyst efficiency monitor.

Some vehicles that are part of the low emission vehicle (LEV) catalyst monitor phase-in, monitor less than 100% of the catalyst volume. Often this is the first catalyst brick of the catalyst system. Partial volume monitoring is done on LEV and ultra low emission vehicle (ULEV) vehicles in order to meet the 1.75 emission standard. The rationale for this strategy is the catalyst nearest the engine deteriorates first, allowing the catalyst monitor to be more sensitive and illuminate the MIL correctly at lower emission standards.

Some applications use partial-volume monitoring, where the rear HO2S is located after the first light-off catalyst can or after the second catalyst can in a three can per bank system (a few applications placed the HO2S in the middle of the catalyst can, between the first and second bricks). For additional HO2S information, refer to the HEATED OXYGEN SENSOR (HO2S) MONITOR .

Index ratios for ethanol (flex fuel) vehicles vary based on the changing concentration of alcohol in the fuel. The threshold to determine a concern typically increases as the percent of alcohol increases. For example, a threshold of 0.5 may be used at E10 (10% ethanol) and 0.9 may be used at E85 (85% ethanol). The thresholds are adjusted based on the percentage of alcohol in the fuel. Standard fuel may contain up to 10% ethanol.

The PCM calibration prevents the catalyst monitor from running on a new vehicle until 60 minutes of time has accumulated with the catalyst temperature greater than 426°C (800°F) or 483 km (300 miles) have accumulated. A replacement PCM or updated calibration does not prevent the catalyst monitor from running.

Scheme 101

Integrated Air Fuel Catalyst Monitor

The integrated air fuel catalyst monitor is an on board strategy designed to monitor the oxygen storage capacity of the catalyst after a deceleration fuel shut off (DFSO) event. The monitor determines the amount of fuel needed to drive the catalyst to a rich condition when starting from an oxygen saturated, lean condition. The monitor is a measure of how much fuel is required to force the catalyst from a lean to a rich condition. The monitor runs during fuel reactivation following a DFSO event. The monitor completes after a calibrated number of DFSO monitoring events have occurred. The integrated air fuel catalyst monitor is used with a heated oxygen sensor (HO2S) or a universal HO2S.

Cold Start Emission Reduction Component Monitor

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

Engine Speed And Spark Timing Monitor

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

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

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

Engine Speed Monitor Entry Conditions

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

Spark Timing Monitor Entry Conditions

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

Cold Start Variable Cam Timing (VCT) Monitor

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

1. DTC: P052A Cold start camshaft position timing over-advanced (Bank 1)
2. DTC: P052B Cold start camshaft timing over-retarded (Bank 1)
3. DTC: P052C Cold start camshaft timing over-advanced (Bank 2)
4. DTC: P052D Cold start camshaft timing over-retarded (Bank 2)
5. Monitor execution: Continuous
6. Monitor sequence: None
7. Monitoring duration: 5 seconds

Cold Start Emission Reduction System Monitor

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

Cold Start Emission Reduction System Monitor Entry Conditions

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

Comprehensive Component Monitor (CCM)

The CCM checks 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 diagnostics (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 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 throttle position or engine coolant temperature are typically checked for opens, shorts, and out-of-range values. This type of monitoring is carried out continuously. Some digital inputs like brake switch or crankshaft position rely on rationality checks that are checking 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 only be carried out under the appropriate test conditions.

Outputs such as coil drivers 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. An idle air control solenoid can be functionally tested by monitoring the idle RPM relative to the target idle RPM. Some tests can only be carried out under the appropriate test conditions. For example, the transmission shift solenoids can only be tested when the PCM commands a shift.

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

Scheme 102

1. Inputs: Air conditioning pressure (ACP) transducer sensor, camshaft position (CMP) sensor, crankshaft position (CKP) sensor, engine coolant temperature (ECT) sensor, fuel rail pressure temperature (FRPT) sensor, fuel tank pressure (FTP) sensor, intake air temperature (IAT) sensor, mass airflow (MAF) sensor, throttle position (TP) sensor.
2. Outputs: EVAP purge valve, EVAP canister vent valve (if equipped), fuel injector, fuel pump (FP), shift solenoid, torque converter clutch (TCC) solenoid, variable camshaft timing (VCT) actuator, wide open throttle A/C cutout (WAC).
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 2 driving cycles when a concern is detected. Many of the CCM tests are also carried out during an on-demand self-test.

Electric Exhaust Gas Recirculation (EEGR) System Monitor

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

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

Scheme 103

Engine Off Timer Monitor

The engine off time is obtained from the powertrain control module (PCM) or the body control module (BCM). If the engine off time is obtained from the BCM, the PCM expects to receive a message with the engine off time from BCM shortly after engine start up. If the message is not available on the CAN or a battery disconnect has occurred, a communication DTC sets.

There are two parts to this test.

The first part determines if the timer is incrementing during engine OFF. The PCM determines the timer is incrementing during engine OFF by comparing the engine coolant temperature value prior to shut down, to the engine coolant temperature value at ignition ON to determine if an engine OFF soak has occurred. For an engine OFF soak to occur, the engine coolant temperature value must be greater than 71°C (160°F) while the engine is running. The timer starts at ignition OFF and the engine coolant temperature value must decrease by greater than 17°C (30°F) before the next ignition ON signal. If the engine off timer indicates a value less than 30 seconds, a DTC sets.

The second part checks the accuracy of the engine off timer. The PCM determines the accuracy of the engine off timer by comparing time in the BCM with the time in the PCM. The timer in the BCM is allowed to count up for 5 minutes and compared to a different clock in the PCM. If the two timers differ by more than 15 seconds, a DTC sets.

Enhanced Thermostat Monitor

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

During a cold start, when the thermostat should be closed, the enhanced thermostat monitor uses intake air temperature, engine speed, and engine load to predict the engine coolant temperature. Once the predicted temperature has exceeded a target temperature for a length of time, the actual engine coolant temperature is compared to its required threshold. This threshold is 11°C (20°F) below the thermostat regulating temperature. If the engine coolant temperature exceeds this threshold, the thermostat is functioning correctly. If the engine coolant temperature is too low, the thermostat may be stuck open and 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 an 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 engine coolant temperature (ECT) sensor or cylinder head temperature (CHT) sensor (if equipped), intake air temperature (IAT) sensor, mass airflow (MAF) sensor, vehicle speed, fuel level input (FLI) and fuel tank pressure (FTP) sensor (if equipped), 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 ignition 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.

Some vehicle applications have an engine OFF natural vacuum (EONV) check as part of the EVAP leak check monitor.

Engine On EVAP Leak Check Monitor - Fiesta

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

Scheme 104

1. The PCM uses inputs from the engine coolant temperature (ECT) sensor, the fuel level input (FLI), the intake air temperature (IAT) sensor, the mass airflow (MAF) sensor, the NVLD ambient air temperature sensor, the vehicle speed sensor (VSS) and the NVLD module to determine conditions of the enhanced EVAP system. The combination of these signals are used by the PCM to determine when to activate the EVAP leak check monitors.
2. The fuel tank pressure is inferred by the PCM based on a message from the NVLD module and other engine parameters. The NVLD module message is based on the position of the NVLD vacuum switch and the NVLD ambient air temperature sensor during calibrated conditions of the EVAP system.
3. The EVAP purge valve creates a vacuum in the fuel tank for the large leak check. In order to detect if the EVAP purge valve will open and allow the vacuum to be released, an EVAP purge valve check is initiated after the NVLD vacuum switch is detected as closed.
4. The NVLD module uses the NVLD vacuum switch to seal the EVAP system from the atmosphere. The NVLD vacuum switch is closed when a vacuum is created in the fuel tank. The NVLD vacuum switch position is monitored for correct operation after the NVLD vacuum switch is detected as closed. Correct operation of the NVLD vacuum switch is determined by opening the EVAP purge valve with the engine OFF to relieve the vacuum in the fuel tank and force the NVLD vacuum switch to open. If the NVLD vacuum switch does not open within a calibrated amount of time, a mechanical switch error is detected. If the NVLD vacuum switch is closed at the beginning of the large leak test, then the EVAP system does not have a large leak and the test is passed. If the NVLD vacuum switch is open at the beginning of the large leak test, the PCM opens the EVAP purge valve to a calibrated amount creating a vacuum in the fuel tank. The NVLD vacuum switch position is monitored by the NVLD module. If the NVLD vacuum switch closes within a calibrated period of time after the EVAP purge valve is open, the system does not have a large leak and the test is passed.
5. On a normally operating EVAP system, a vacuum is generated inside the fuel tank as the temperature of the fuel decreases.

Engine On EVAP Leak Check Monitor - All Others

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

Scheme 105

1. The EVAP purge valve controls the flow of vacuum from the engine and creates a target vacuum on the fuel tank.
2. The EVAP canister vent valve seals the EVAP system from the atmosphere. It is closed by the PCM (100% duty cycle) to allow the EVAP purge valve to achieve 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. Some vehicle applications with the engine on EVAP leak check monitor use a remote inline FTP sensor. Once the target vacuum on the fuel tank is achieved, the change in fuel tank vacuum over a calibrated period of time determines if a leak exists.
4. If the initial target vacuum cannot be reached, DTC P0455 (gross leak detected) sets. The engine on EVAP leak check monitor aborts and does not continue with the leak check portion of the test. For some vehicle applications, if the initial target vacuum cannot be reached after a refueling event and the purge vapor flow is excessive, DTC P0457 (fuel cap off) sets. If the initial target vacuum is exceeded, a system flow concern exists and DTC P1450 (unable to bleed-up fuel tank vacuum) is set. The engine on EVAP leak check monitor aborts and does not continue with the leak check portion of the test. If the vacuum increase is quicker than expected, a blocked fuel vapor tube is suspected and if confirmed after an intrusive test, DTC P144A sets. If the target vacuum is achieved on the fuel tank, the change in the fuel tank vacuum (bleed-up) is calculated for a calibrated period of time. The calculated change in fuel tank vacuum is compared to a calibrated threshold for a leak from an opening of 1.016 mm (0.040 inch) in the enhanced EVAP system. If the calculated bleed-up is less than the calibrated threshold, the enhanced EVAP system passes. If the calibrated bleed-up exceeds the calibrated threshold, the test aborts. The test can be repeated up to 3 times. If the bleed-up threshold is still being exceeded after 3 tests, a vapor generation test is carried out before DTC P0442 (small leak detected) sets. This is accomplished by returning the enhanced EVAP system to atmospheric pressure by closing the EVAP purge valve and opening the EVAP canister vent valve. Once the FTP sensor observes the fuel tank is at atmospheric pressure, the EVAP canister vent valve closes and seals the enhanced EVAP system. The fuel tank pressure build-up over a calibrated period of time is compared to a calibrated threshold for pressure build-up due to vapor generation. If the fuel tank pressure build-up exceeds the threshold, the leak test results are invalid due to vapor generation. The engine on EVAP leak check monitor attempts to repeat the test again. If the fuel tank pressure build-up does not exceed the threshold, the leak test results are valid and DTC P0442 sets.
5. If the 1.016 mm (0.040 inch) test passes, the test time is extended to allow the 0.508 mm (0.020 inch) test to run. The calculated change in fuel vacuum over the extended time is compared to a calibrated threshold for a leak from a 0.508 mm (0.020 inch) opening. If the calculated bleed-up exceeds the calibrated threshold, the vapor generation test is run. If the vapor generation test passes (no vapor generation), an internal flag sets in the PCM to run a 0.508 mm (0.020 inch) test at idle (vehicle stopped). On the next start following a long engine OFF period, the enhanced EVAP system is sealed and evacuated for the first 10 minutes of operation. If the appropriate conditions are met, a 0.508 mm (0.020 inch) leak check is conducted at idle. If the test at idle fails, DTC P0456 sets. There is no vapor generation test with the idle test.
6. The malfunction indicator lamp (MIL) is activated for DTCs P0442, P0455, P0456, P0457, and P1450 after 2 occurrences of the same concern and for DTC P144A 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, and P0453 are tested as part of the comprehensive component monitor (CCM).

Engine Off Natural Vacuum (EONV) EVAP Leak Check Monitor

The EONV EVAP leak check monitor is executed during ignition 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

Scheme 106

1. The EVAP purge valve is normally closed at ignition OFF.
2. The normally open EVAP canister vent valve 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 EVAP canister vent valve 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 as a means to detect a leak in the EVAP system. At ignition 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 ignition 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 ignition OFF. After ignition OFF the normally open EVAP canister vent valve 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 EVAP canister vent valve is closed by the PCM (100% duty cycle) and seals the EVAP system from the atmosphere. If the pressure on the fuel tank decreases after the EVAP system is sealed, the EONV EVAP leak check monitor begins to monitor the fuel tank pressure. When the target vacuum is exceeded within the calibrated amount of time the test completes and the fuel tank pressure and time since ignition OFF information is stored. If the target vacuum is not reached in the calibrated amount of time, a leak is suspected and the fuel tank pressure and time since ignition OFF information is stored. If the pressure on the fuel tank increases after the EVAP system is sealed, but does not exceed the target pressure within a calibrated amount of time, the EVAP canister vent valve is opened to allow the fuel tank pressure to again stabilize with the atmosphere. After a calibrated amount of time the EVAP canister vent valve is closed by the PCM and seals the EVAP system. When the fuel tank pressure exceeds either the target pressure or vacuum within the calibrated amount of time, the test completes and the fuel tank pressure and time since ignition OFF information is stored. If the target pressure or vacuum is not reached in the calibrated amount of time, a leak is suspected and the fuel tank pressure and time since ignition OFF information is stored. On ISO 14229 vehicles, a fast initial response occurs during the first 4 tests after the battery is disconnected or the DTCs are cleared. The PCM processes unfiltered data to quickly indicate a fault is present. The MIL illuminates if the PCM suspects a leak within 2 consecutive trips after a DTC clear or a battery disconnect using the fast initial response logic. A step change logic becomes active after the 4th EONV monitor test. The step change logic detects an abrupt change from a no leak condition to a suspected leak condition. The MIL illuminates if the PCM suspects a leak within 2 consecutive trips using the step change logic. During the EONV monitor test the PCM uses an exponentially weighted moving average to filter test data. The PCM uses this average after the fourth EONV test and illuminates the MIL on the first trip when the exponentially weighted moving average is greater than a calibrated threshold. When a leak is suspected, DTC P0456 sets and the MIL is illuminated. On non-ISO 14229 vehicles, when a leak is suspected, the PCM uses the stored fuel tank pressure and time since ignition OFF information from an average run of 4 tests to suspect a leak. Some vehicles use an alternative method of a single run of 5 tests to determine the presence of a leak. If a leak is still suspected after 2 consecutive runs of 4 tests, (8 total tests) or one run of 5 tests, DTC P0456 sets and the MIL is illuminated.
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 EVAP canister vent valve and the stored test information. If the separate microprocessor is unable to control the EVAP canister vent valve or communicate with other processors, DTC P260F sets.
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.

Natural Vacuum Leak Detection (NVLD) Small Leak Monitor

The engine off NVLD small leak monitor is executed by the individual components internal to the NVLD module as follows

1. The PCM uses inputs from the ECT sensor, the IAT sensor, the MAF sensor, the VSS and the NVLD module to determine conditions of the enhanced EVAP system. The combination of these signals are used by the PCM to determine when to activate the EVAP leak check monitors.
2. When the ignition is turned OFF and the calibrated conditions are met the PCM sends a message to the NVLD module to begin the engine off NVLD monitor.
3. The EVAP purge valve is normally closed with the ignition OFF.
4. The NVLD leak check monitor uses the naturally occurring change in fuel tank pressure as a means to detect a leak in the EVAP system. The small leak check monitor is controlled by a separate low power consuming microprocessor inside the NVLD module. The small leak check monitor is executed with the ignition OFF, after the engine running EVAP leak check monitor is completed. The heat generated while the engine is running warms the fuel in the fuel tank. When the engine is turned OFF a natural vacuum is generated by the fuel cooling in the fuel tank. On a normally operating EVAP system this vacuum closes the NVLD vacuum switch. The NVLD vacuum switch position is checked after 10 minutes from engine shut down. If the NVLD vacuum switch is closed the small leak monitor passes. If, after 10 minutes from engine shut down the NVLD vacuum switch is not closed, and the NVLD ambient air temperature sensor change is more than 8°C (14°F) over the next 24 hour period without the vacuum switch closing, the test fails. The PCM receives a message from the NVLD module at ignition ON and then engine running, indicating the EVAP system has either passed or failed the small leak test. A vacuum decay test is executed as a rationality test to the NVLD small leak check monitor. The vacuum decay rate is determined by the calculated fuel tank pressure, leak size, the fuel tank fill level, the NVLD ambient temperature sensor, and the fuel type. Tank pressure is determined by tank fill level, AAT sensor, the EVAP purge valve opening, and NVLD vacuum switch position prior to engine OFF. If either the NVLD small leak check monitor passes or the vacuum decay test passes the PCM considers the EVAP system passed the leak test. If the NVLD small leak check monitor fails and the vacuum decay test passes the PCM considers the EVAP system passed the leak test
5. On a normally operating EVAP system, a vacuum is generated inside the fuel tank as the temperature of the fuel decreases.

Exhaust Gas Recirculation (EGR) System Monitor - EGR System Module (ESM)

The EGR system monitor is an on board strategy designed to test the integrity and flow characteristics of the EGR system. The monitor is activated during EGR system operation and after certain base engine conditions are satisfied. Input from the engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), throttle position (TP), and crankshaft position (CKP) sensors is required to activate the 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 an on demand self-test.

Scheme 107

1. The differential pressure feedback EGR sensor and circuit are continuously tested for opens and shorts. The monitor checks for the differential pressure feedback EGR circuit voltage to exceed the maximum or minimum allowable limits. The diagnostic trouble codes (DTCs) associated with this test are P0405 and P0406.
2. The EGR vacuum regulator solenoid is continuously tested for opens and shorts. The monitor looks for an EVR circuit voltage that is inconsistent with the EVR circuit commanded output state. The DTC associated with this test is P0403.
3. The test for a stuck open EGR valve or EGR flow at idle is continuously carried out at idle (TP sensor indicating closed throttle). The monitor compares the differential pressure feedback EGR circuit voltage at idle to the differential pressure feedback EGR circuit voltage stored during key ON engine OFF (KOEO) to determine if EGR flow is present at idle. The DTC associated with this test is P0402.
4. The differential pressure feedback EGR sensor hoses are tested once per drive cycle for disconnect and plugging. The test is carried out with the EGR valve closed and during a period of acceleration. The powertrain control module (PCM) momentarily commands the EGR valve closed. The monitor looks for the differential pressure feedback EGR sensor voltage to be inconsistent for a no flow voltage. A voltage increase or decrease during acceleration while the EGR valve is closed may indicate a concern with a signal hose during this test. The DTCs associated with this test are P1405 and P1406 (differential pressure feedback EGR systems only).
5. The EGR flow rate test is carried out during a steady state when the engine speed and load are moderate and the EGR vacuum regulator duty cycle is high. The monitor compares the actual differential pressure feedback EGR circuit voltage to a desired EGR flow voltage for that state to determine if the EGR flow rate is acceptable or insufficient. This is a system test and may trigger a DTC for any concern causing the EGR system to not operate correctly. The DTC associated with this test is P0401. DTC P1408 is similar to P0401 but is carried out during key ON engine running (KOER) self-test conditions.
6. The malfunction indicator lamp (MIL) is activated after one of the above tests fails on 2 consecutive drive cycles.

Fuel System Monitor

The fuel system monitor is an on board strategy designed to monitor the fuel control system. The fuel control system uses fuel trim tables stored in the powertrain control module (PCM) keep alive memory (KAM) to compensate for the variability that occurs in fuel system components due to normal wear and aging. Fuel trim tables are based on air mass. 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 a short term fuel trim. Refer to POWERTRAIN CONTROL SOFTWARE , FUEL TRIM . Long term fuel trim relies on the fuel trim tables and short term fuel trim refers to the desired air to 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 to fuel ratio during closed-loop operation. Short term fuel trim and long term fuel trim work together. If the HO2S indicates the engine is running rich, the PCM corrects the rich condition by moving the short term fuel trim into 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%. Inputs from the engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), and mass airflow (MAF) sensors are required to activate the fuel trim system, which in turn activates the fuel system monitor. Once activated, the fuel system monitor looks for the fuel trim tables to reach the adaptive clip (adaptive limit) and LAMBSE to exceed a calibrated limit. The fuel system monitor stores the appropriate DTC when a concern is detected as described below.

Scheme 108

1. The HO2S detects the presence of oxygen in the exhaust and provides the PCM with feedback indicating air to fuel ratio.
2. A correction factor is added to the fuel injector pulse width calculation and the mass airflow 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 LAMBSE parameter increases, air to fuel control suffers and emissions increase. When LAMBSE exceeds a calibrated limit and the fuel trim table has clipped, the fuel system monitor sets a DTC as follows: The DTCs associated with the monitor detecting a lean shift in fuel system operation are P0171 (Bank 1) and P0174 (Bank 2). The DTCs associated with the monitor detecting a rich shift in fuel system operation are P0172 (Bank 1) and P0175 (Bank 2).
4. The malfunction indicator lamp (MIL) is activated after a concern is detected on 2 consecutive drive cycles. Typical fuel system monitor entry conditions: RPM range greater than idle Air mass range greater than 5.67 g/sec (0.75 lb/min) Purge duty cycle of 0% Typical fuel monitor thresholds: Lean Condition Concern: LONGFT greater than 25%, SHRTFT greater than 5% Rich Condition Concern: LONGFT less than 25%, SHRTFT less than 10%

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 fuel control or stream 1 HO2S are 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 camshaft position (CMP), crankshaft position (CKP), engine coolant temperature (ECT) or cylinder head temperature (CHT), fuel rail pressure temperature (FRPT), fuel tank pressure (FTP), intake air temperature (IAT), mass airflow (MAF), manifold absolute pressure (MAP), and throttle position (TP) sensors and the vehicle speed sensor (VSS) to activate the HO2S monitor. The fuel system monitor and misfire detection monitor must also have completed successfully before the HO2S monitor is enabled.

For applications using a universal HO2S in the upstream or stream 1 position, there are additional DTCs such as heater temperature control, additional circuit diagnostics, lack of movement, and FAOS catalyst optimization.

Scheme 109

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 to 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 to 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 concerns can 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 concern. 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. A functional test of the rear HO2Ss is done during normal vehicle operation. The peak rich and lean voltages are continuously monitored. Voltages that exceed the calibrated rich and lean thresholds indicate a functional sensor. If the voltages have not exceeded the thresholds after a long period of vehicle operation, the air to fuel ratio may be forced rich or lean in an attempt to get the rear sensor to switch. This situation normally occurs only with a green, less than 804.7 km (500 miles), catalyst. If the sensor does not exceed the rich and lean peak thresholds, a concern is indicated. Also, a deceleration fuel shut off rear HO2S response test is done during a deceleration fuel shut off (DFSO) event. Carrying out the HO2S response test during a DFSO event helps to isolate a sensor concern from a catalyst concern. The response test monitors how quickly the sensor switches from a rich to lean voltage. It also monitors if there is a delay in the response to the rich or lean condition. If the sensor responds very slowly to the rich to lean voltage switch or is never greater than a rich voltage threshold or less than a lean voltage threshold, a concern is indicated.
3. The malfunction indicator lamp (MIL) is activated after a concern is detected on 2 consecutive drive cycles.

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 engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), and mass airflow (MAF) sensors is required to enable the monitor. The misfire detection monitor is also carried out during an on-demand self-test.

Scheme 110

1. The powertrain control module (PCM) synchronized ignition spark is based on information received from the crankshaft position (CKP) sensor. The CKP sensor 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 sensor signal edges and the crankshaft rotational velocity and acceleration. By comparing the accelerations of each cylinder event, the power loss of each cylinder is determined. When the power loss of a particular cylinder is sufficiently less than a calibrated value and other criteria are met, then the suspect cylinder is determined to have misfired.
4. The malfunction indicator lamp (MIL) is activated after one of the above tests fail on 2 consecutive drive cycles.

Low Data Rate (LDR) System

The LDR misfire monitor uses a low data rate CKP sensor signal which indicates one position reference at 10 degrees before top dead center (BTDC) for each cylinder event. The PCM uses the CKP sensor signal to calculate the crankshaft speed and acceleration for each cylinder. The crankshaft acceleration is then processed to detect a sporadic, single-cylinder misfire patterns or multi-cylinder misfire patterns. 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. Refer to the GENERIC MISFIRE PROCESSING for more information.

High Data Rate (HDR) System

The HDR misfire monitor uses a high data rate CKP sensor signal which indicates 18 position references per crankshaft revolution. This high resolution signal is processed using 2 different algorithms. The first algorithm is optimized to detect hard misfires on one or more continuously misfiring cylinders. The low pass filter filters the high resolution crankshaft velocity signal to remove some of the crankshaft torsional vibrations that degrade signal to noise. Two low pass filters are used to enhance detection capability: a base filter and a more aggressive filter to enhance single-cylinder capability at higher RPM. This significantly improves detection capability for continuous misfires on single cylinders up to red line. The second algorithm, called pattern cancellation, is optimized to detect low rates of misfire. The algorithm learns the normal pattern of cylinder accelerations from the mostly good firing events and is then able to accurately detect deviations from that pattern. Both the hard misfire algorithm and the pattern cancellation algorithm produce a deviant cylinder acceleration value, which is used in evaluating misfire in the GENERIC MISFIRE PROCESSING .

Due to the high data processing requirements, the HDR algorithms may be implemented by the PCM in a separate chip. The chip carries out the HDR algorithm calculations and sends the deviant cylinder acceleration values to the PCM microprocessor for additional processing as described below. The chip requires correct operation of the CKP and camshaft position (CMP) sensor inputs. DTC P1336 sets if the chip detects noise on the CKP sensor input or if the chip is unable to synchronize with the missing tooth location. DTC P1336 points to noise present on the CKP sensor input or a lack of synchronization between the CMP and CKP sensors.

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/cylinder 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 at high RPM with light load conditions, will 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 is evaluated every 200 revolution period (Type A) and compared to a threshold value achieved from an engine speed/load table. This misfire threshold is designed to prevent damage to the catalyst due to sustained excessive temperature 899°C (1, 650°F) for Pt/Pd/Rh advanced washcoat and 982°C (1, 800°F) for Pd-only high tech washcoat. If the misfire threshold is exceeded and the catalyst temperature model calculates a catalyst mid-bed temperature that exceeds the catalyst damage threshold, the 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.

If a single cylinder is determined to be consistently misfiring in excess of the catalyst damage criteria, the fuel injector to that cylinder is shut off to prevent catalyst damage for a calibrated period of time, typically 30 to 60 seconds. Up to 2 cylinders may be disabled at the same time on 6 and 8 cylinder engines and one cylinder on 4 cylinder engines. After the calibrated period of time has elapsed, the injector is re-enabled. If misfire on that cylinder is detected again after 200 revolutions (about 5 to 10 seconds), the fuel injector is shut off again and the process repeats until the misfire is no longer present. Note that ignition coil primary circuit failures trigger the same type of fuel injector disablement. For additional information, refer to COMPREHENSIVE COMPONENT MONITOR (CCM) .

The misfire rate is also evaluated every 1, 000 revolution period and compared to a single (type B) threshold value to indicate an emission-threshold concern, which can be either a single 1, 000 over-rev event from startup or 4 subsequent 1, 000 over-rev events on a drive cycle after start-up. Many vehicles set DTC P0316 if the type B 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. If the misfire is detected but it can not be attributed to a specific cylinder, DTC P0300 is stored.

Rough Road Detection

The misfire detection monitor may include a rough road detection system to eliminate false misfire indications due to rough road conditions. The rough road detection system uses data from the anti-lock brake system (ABS) wheel speed sensors for estimating the severity of rough road conditions. This is a more direct measurement of rough road over other methods which are based on drive line feedback via crankshaft velocity measurements. It improves accuracy over these other methods since it eliminates interactions with actual misfire.

In the event of a rough road detection system failure, the rough road detection output is ignored and the misfire detection monitor remains active. A rough road detection system failure could be caused by a failure in any of the input signals to the algorithm. This includes the ABS wheel speed sensors, brake pedal sensor, or controller area network (CAN) hardware concerns. Specific DTCs indicate the source of these component concerns.

A redundant check is also carried out on the rough road detection system to verify it is not stuck high due to other unforeseen causes. If the rough road detection system indicates rough road during low vehicle speed conditions where it is not expected, the rough road detection output is ignored and the misfire monitor remains active.

Profile Correction

Profile correction software is used to learn and correct 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. The LDR system learns one profile correction factor per cylinder (that is, 4 correction factors for a 4 cylinder engine), while the HDR system learns 36, 40 or 60 correction factors depending on the number of crankshaft wheel teeth (that is, 35 for some V6 or V8 engines, 39 for V10 engines, 58 for some 4 cylinder engines and some V6 engines).

The corrections are calculated from several engine cycles of misfire sample interval data. The correction factors are the average of a selected number of samples. In order to assure the accuracy of these corrections, a tolerance is placed on the incoming values such that an individual correction factor must be repeatable within the tolerance during learning. This is to reduce the possibility of learning corrections on rough road conditions which could limit misfire detection capability and to help isolate misfire diagnoses from other crankshaft velocity disturbances.

To prevent any fueling or combustion differences from affecting the correction factors, learning is done during deceleration fuel shut off (DFSO). This can be done during closed throttle, nonbraking, defueled decelerations in the 97 to 64 km/h (60 to 40 mph) range after exceeding 97 km/h (60 mph) (likely to correspond to a freeway exit condition). In order to minimize the learning time for the correction factors, a more aggressive DFSO strategy may be used when the conditions for learning are present. The corrections are typically learned in a single 97 to 64 km/h (60 to 40 mph) deceleration, but may take up to 3 such decelerations or a higher number of shorter decelerations.

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 battery disconnection or loss of keep alive memory (KAM), the correction factors are lost and must be relearned. If the software is unable to learn a profile after three, 97 to 64 km/h (60 to 40 mph) deceleration cycles, DTC P0315 is set.

Neutral Profile Correction And Non-Volatile Memory

Neutral profile learning is used at end of line to learn profile correction through a series of one or more neutral engine RPM throttle snaps. This allows the misfire monitor to be activated at the assembly plant. A scan tool command is required to enable neutral profile correction learning. Learning profile correction factors at high-speed (3, 000 RPM) neutral conditions versus during 60-40 mph decels optimizes correction factors for higher RPMs where they are most needed and eliminates driveline or transmission and road noise effects. This improves signal to noise characteristics which means improved detection capability.

The profile correction factors learned at the assembly plant are stored into non-volatile memory. This eliminates the need for specific customer drive cycles. However, misfire profiles may need to be relearned using a scan tool procedure if major engine work is done or a new PCM is installed. Re-learning is not required for a reflash.

The neutral profile correction strategy is only available on selected vehicles.

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 cam-lock 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 inadvertent disconnection of the lines after a vehicle is repaired causes either an immediate engine stall or does not allow the engine to be restarted. In the event the vehicle does not stall if the line between the intake manifold and PCV valve is inadvertently disconnected, the vehicle has a large vacuum leak that causes the vehicle to run lean at idle. This illuminates the malfunction indicator lamp (MIL) after 2 consecutive driving cycles and stores one or more of the following diagnostic trouble codes (DTCs): P2195 Lack of HO2S sensor switches (bank 1), P2197 Lack of HO2S sensor switches (bank 2), P0171 fuel system lean (bank 1) or P0174 fuel system lean (bank 2).

The PCV monitor sets DTC P2282 if a PCV vacuum hose is disconnected, or if a large air leak between the throttle body and intake valves is present. A fast idle speed symptom may be present when the DTC P2282 is set.

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

Thermostat Monitor

The thermostat monitor is designed to verify correct thermostat operation. This monitor is executed once per drive cycle and has a monitor run duration of 300-800 seconds. If a concern is present, diagnostic trouble code (DTC) P0125 or P0128 is set and the malfunction indicator lamp (MIL) is illuminated.

The monitor checks the engine coolant temperature (ECT) or cylinder head temperature (CHT) sensor to warm up in a predictable manner when the engine is generating sufficient heat. A timer is initialized while the engine is at moderate load and the vehicle speed is above a calibrated limit. The target timer value is based on ambient air temperature at start-up. If the timer exceeds the target time and ECT or CHT has not warmed up to the target temperature, a concern is indicated. The test runs if the start-up intake air temperature from the intake air temperature (IAT) sensor is at, or below the target temperature. A 2-hour engine OFF soak time is also required to enable the monitor and to prevent erasing of any pending DTCs during a hot soak. This soak time feature also prevents false-passes of the monitor when the engine coolant temperature rises after the engine is turned OFF during a short engine OFF soak period.

The target temperature is calibrated to within 11°C (20°F) less than the thermostat regulating temperature. For a typical 90°C (195°F) thermostat, the target temperature would be calibrated to 79°C (175°F). Some vehicle calibrations may lower the target temperature to less than 27°C (50°F) for vehicles that do not warm-up to thermostat regulating temperatures in the 11°C (20°F) to 27°C (50°F) ambient temperature range.

Scheme 111

1. Inputs: ECT or CHT, IAT, engine LOAD (from mass airflow (MAF) sensor) and vehicle speed input. Typical monitor entry conditions: vehicle speed greater than 24 km/h (15 mph) intake air temperature at start-up is between -7°C (20°F) and target thermostat temperature engine load greater than 30% engine OFF (soak) time greater than 2 hours
2. Output: MIL.

Variable Camshaft Timing (VCT) Monitor

The VCT output driver in the powertrain control module (PCM) is checked electrically for opens or 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 .