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ENGINE CONTROL COMPONENTSNOTE: Transmission inputs which are not described are discussed in the applicable diagrams/repair information transmission system.
Accelerator Pedal Position (APP) Sensor
The APP sensor is an input to the powertrain control module (PCM) and used to determine the amount of torque requested by the operator. Depending on the application, either a 2-track or 3-track APP sensor is used.
2-Track APP Sensor
There are 2 pedal position signals in the sensor. Both signals, APP 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 1 signal has a concern. The PCM determines if a signal is incorrect by calculating where it should be, inferred from the other signals. If a concern is present with one of the circuits the other input is used. There are 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 then converts these degrees to counts, which is the input to the torque based strategy. For additional information, refer to Torque Based Electronic Throttle Control (ETC). Description and Operation
Typical 2-Track APP Sensor:
3-Track APP Sensor
There are 3 pedal position signals in the sensor. Signal 1, APP, 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 then 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.
Typical 3-Track APP Sensor:
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:
- to the PCM supplying battery positive (B+) voltage when the brake pedal is applied.
- 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.
- to the ABS traction control/stability assist module. The ASS 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.
Typical BPP Switch:
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.
Vehicles with 2 CMP sensors are equipped with variable camshaft timing (VCT). The second sensor is used to identify the position of the camshaft on bank 2.
There are 2 types of CMP sensors: the 2-pin variable reluctance type sensor and the 3-pin Hall-effect type sensor.
Typical Variable Reluctance CMP Sensor:
Typical Hall-effect CMP Sensor:
Canister Vent (CV) Solenoid
During the evaporative emissions (EVAP) leak check monitor, the CV solenoid seals the EVAP canister from the atmospheric pressure. This allows the EVAP canister purge valve to obtain the target vacuum in the fuel tank during the EVAP leak check monitor.
Typical Canister Vent (CV) Solenoid:
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 powertrain control module (PCM) uses the information from the CACT sensor to refine the estimate of the air flow rate through the throttle and to determine the desired boost pressure. The CACT sensor for a speed density system is integral with the turbocharger boost pressure (TCBP) sensor.
Typical CACT Sensor Integrated With A TCBP Sensor:
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 (SIG RTN) circuit. The CPP input to the PCM is used to detect a reduction in engine load. The PCM uses the load information for mass air flow and fuel calculations.
Typical Cluch Pedal Position (CPP) Switch:
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 has 3 different modes of operation: engine crank, engine running, and CMP failure mode effects management (FMEM). For additional information, refer to Ignition Systems. Ignition Systems
Typical Coil On Plug (COP):
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.
Typical 4-Tower Coil Pack:
Typical 6-Tower Coil Pack:
Cooling Fan Clutch
The cooling fan clutch is an electrically actuated viscous clutch that consists of 3 main elements:
- a working chamber
- a reservoir chamber
- 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 clutch speed. The cooling fan clutch 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 (ECT), engine oil temperature (EOT), transmission fluid temperature (TFT), intake air temperature (IAT), 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.
Cooling Fan Clutch With FSS:
Crankshaft Position (CKP) Sensor
The CKP sensor is a magnetic transducer mounted on the engine block adjacent to a pulse wheel located on the crankshaft. By monitoring the crankshaft mounted pulse wheel, the CKP is the primary sensor for ignition information to the PCM. The pulse wheel has a total of 35 teeth spaced 10 degrees apart with 1 empty space for a missing tooth. 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 signal to determine if a misfire has occurred by measuring rapid decelerations between teeth.
Typical CKP Sensor:
Cylinder Head Temperature (CHT) 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.
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. Powertrain Control Software
Typical CHT Sensor:
Differential Pressure Feedback Exhaust Gas Recirculation (EGR) Sensor
The differential pressure feedback EGR sensor is a ceramic, capacitive-type pressure transducer that monitors the differential pressure across a metering orifice located in the orifice tube assembly. The differential pressure feedback EGR sensor receives this signal through 2 hoses referred to as the downstream pressure hose (REF SIGNAL) and upstream pressure hose (HI SIGNAL). The HI and REF hose connections are marked on the differential pressure feedback EGR sensor housing for identification (note the HI signal 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.
Differential Pressure Feedback EGR Sensor:
Differential Pressure Feedback EGR Sensor - Tube Mounted
The tube mounted differential pressure feedback EGR sensor is identical in operation as the larger plastic differential pressure feedback EGR sensors and uses a 1.0 volt offset. The HI and REF hose connections are marked on the side of the sensor.
Differential Pressure Feedback EGR Sensor - Tube Mounted:
Electric Exhaust Gas Recirculation (EEGR) Valve
Depending on the application, the EEGR valve is 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.
EEGR Motor/Valve Assembly:
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 in-line. The parallel design has the motor under the bore parallel to the plate shaft. The motor housing is integrated into the main housing. The in-line design has a separate motor housing. 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. The closed throttle plate hard stop is used to prevent the throttle from binding in the bore. This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle. For additional information, refer to Torque Based Electronic Throttle Control (ETC). Description and Operation
Typical In-Line TAC Design:
Typical Parallel TAC Design:
Electronic Throttle Body Throttle Position Sensor (ETBTPS)
The ETBTPS has 2 signal circuits in the sensor for redundancy. The redundant ETBTPS signals are required for increased monitoring. The first ETBTPS signal (TPS1-NS) has a negative slope (increasing angle, decreasing voltage) and the second signal (TPS2-PS) has a positive slope (increasing angle, increasing voltage). The 2 ETBTPS signals make sure the PCM receives a correct input even if one signal has a concern. There is 1 reference voltage circuit and 1 signal return circuit for the sensor that are shared with the reference voltage circuits and signal return circuits used by the APP sensor. For additional information, refer to Torque Based Electronic Throttle Control (ETC). Description and Operation
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 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 measures the temperature of the engine coolant. The PCM uses the ECT input for fuel control and for cooling fan control. There are 3 types of ECT sensors; threaded, push-in, and twist-lock. The ECT sensor is located in an engine coolant passage.
Typical Thread-Type ECT Sensor:
Engine Oil Temperature (EOT) Sensor
The EOT 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 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 EOT sensor measures the temperature of the engine oil. The sensor is typically threaded into the engine oil lubrication system. The PCM uses the EOT sensor input in conjunction with other PCM inputs to determine oil degradation.
The PCM uses EOT sensor input to initiate a soft engine shutdown to prevent engine damage from occurring as a result of high oil temperatures. Whenever engine RPM exceeds a calibrated level for a certain period of time, the PCM begins reducing power by disabling engine cylinders.
On VCT applications, the PCM uses the EOT sensor input to adjust the VCT control gains and logic for camshaft timing.
Typical EOT Sensor:
Evaporative Emission (EVAP) Canister Purge Valve
The EVAP canister purge valve 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 canister purge valve is a normally closed valve. The EVAP canister purge valve controls the flow of vapors by way of a solenoid, eliminating the need for an electronic vacuum regulator and vacuum diaphragm. For E-Series, Escape/Mariner, Expedition, F-Series, Fusion 2.5L, Fusion 3.0L, Milan and Navigator, the PCM outputs a duty cycle between 0% and 100% to control the EVAP canister purge valve. For all others, the PCM outputs a variable current between 0 and 1,000 mA to control the EVAP canister purge valve.
Typical EVAP Canister Purge Valve:
Evaporative Emission (EVAP) Canister Purge Check Valve
The EVAP canister purge check valve is used on turbocharged engines to prevent boost pressure from forcing open the EVAP canister 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 canister purge check valve is in an indeterminate state. The EVAP canister purge check valve is an integral part of the purge valve assembly.
Typical EVAP Canister Purge Check Valve:
Exhaust Gas Recirculation (EGR) Orifice Tube Assembly
The EGR orifice tube assembly is a section of tubing connecting the exhaust system to the intake manifold. The assembly provides the flow path for the EGR to the intake manifold and also contains the metering orifice and 2 pressure pick-up tubes. The internal metering orifice creates a measurable pressure drop across it as the EGR valve opens and closes. This pressure differential across the orifice is picked up by the differential pressure feedback EGR sensor which provides feedback to the PCM.
EGR Orifice Tube Assembly:
Exhaust Gas Recirculation (EGR) System Module (ESM)
The ESM is an integrated differential pressure feedback EGR system that 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 (MAP). This MAP 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.
ESM:
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.
EGR Vacuum Regulator Solenoid:
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 flow of EGR. 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 about 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 diagnostic trouble code (DTC) if the test criteria is not met. The EGR valve flow rate is not measured directly as part of the diagnostic procedures.
Typical EGR Valve:
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 variable speed electric fan(s):
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).
EDGE/MKX, FLEX, MKS, MKT, TAURUS, FUSION/MILAN/MKZ, CROWN VICTORIA/GRAND MARQUIS, TOWN CAR: FCV DUTY CYCLE OUTPUT FROM PCM (negative duty cycle)
For 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.
2.0L Focus And Transit Connect (With A/C): PCM FC Output State For Cooling Fan Speeds:
2.5L Escape: PCM FC Output State For Cooling Fan Speeds:
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.
Cooling Fan Clutch With FSS:
