Engine Controls - Description and Operation - (Hybrid): Overview Ford Escape I facelift

OBD Overview

The objectives of the OBD system are to improve air quality by reducing high emissions caused by emission related malfunctions, reducing the time between the occurrence of a malfunction and its detection and repair, and assisting in the diagnosis and repair of emission related problems. A malfunction indicator lamp (MIL) is required to illuminate and alert the driver of the malfunction and the need to repair the emission control system. A diagnostic trouble code (DTC) is required to assist in identifying the system or component associated with the fault.

The OBD system monitors virtually all emission control systems and components that can affect tailpipe or evaporative emissions. In most cases, malfunctions must be detected before emissions exceed 1.5 times the applicable 100,000, 120,000, or 150,000 mile emission standard. Partial zero emission vehicles (PZEV) can use malfunction criteria of 2.5 in lieu of the 1.5 standard whenever required. If a system or component exceeds emission thresholds or fails to operate within a manufacturer's specifications, a DTC is stored and the MIL is illuminated within 2 driving cycles.

The OBD system monitors for malfunctions either continuously, regardless of driving mode, or non-continuously, once per drive cycle during specific drive modes. A pending DTC is stored in the powertrain control module (PCM) keep alive memory (KAM) when a malfunction is initially detected. This pending DTC is stored as long as the malfunction is present and it may be erased on the power up after 1 drive cycle without malfunction. However, if the malfunction is still present after 2 consecutive drive cycles, the MIL is illuminated. Once the MIL is illuminated, 3 consecutive drive cycles without a malfunction 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, and standardized DTCs and terminology. Examples of standard diagnostic information are freeze frame data and Inspection Maintenance (IM) Readiness Indicators.

Freeze frame data describes data stored in the KAM at the point the malfunction is initially detected. Freeze frame data consists of parameters such as engine RPM and load, state of fuel control, spark, and warm-up status. Freeze frame data is stored at the time the first malfunction is detected, however, previously stored conditions are replaced if a fuel or misfire fault is detected. This data is accessible with the diagnostic tool to assist in repairing the vehicle.

OBD IM readiness indicators show whether all of the OBD monitors have been completed since the last time the KAM or the PCM DTCs were cleared. Ford also stores a P1000 DTC 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 IM readiness indicators must show that all monitors have been completed prior to the OBD check.

The following provides 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 is also provided. These illustrations only provide a high level overview.

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 comprehensive component monitor (CCM) illustration has numerous components and signals involved and are shown generically. When referring to the illustrations, match the numbers to the corresponding numbers in the monitor descriptions for a better comprehension of the monitor and associated DTCs.

These icons are used in the illustrations of the OBD monitors and throughout ENGINE PERFORMANCE articles.

Scheme 125

Catalyst Efficiency Monitor Overview

The catalyst efficiency monitor uses precatalyst and post catalyst heated oxygen sensors (HO2S) to infer the hydrocarbon (HC) efficiency based the on the oxygen storage capacity of the catalyst. Under normal, closed loop fuel conditions, high efficiency catalysts have significant oxygen storage. This makes the switching frequency of the post catalyst HO2S (B) very slow and reduces the amplitude of those switches as compared to the switching frequency and amplitude of the precatalyst HO2S (A). As catalyst efficiency deteriorates due to thermal and/or chemical deterioration, its ability to store oxygen declines. The post catalyst HO2S (B) signal begins to switch more rapidly with increasing amplitude, approaching the switching frequency and amplitude of the precatalyst HO2S (A).

High Efficiency Catalyst (Normal)

Scheme 126

Low Efficiency Catalyst

Scheme 127

Note. The primary failure mode for high mileage catalysts is chemical deterioration (phosphorus deposition on the front brick of the catalyst), not thermal deterioration as is often assumed.

Escape Hybrid Hardware and Monitor Operation

1. The Escape Hybrid exhaust system uses 2 of 3 HO2S. The front HO2S is the primary fuel control sensor. This sensor is the first HO2S in the exhaust stream and is referred to as the HO2S11. The last HO2S downstream in the exhaust system is used to monitor the catalyst and is referred to as HO2S12. The middle HO2S in the exhaust stream does not provide any input to the powertrain control module (PCM). For additional HO2S information, refer to «HEATED OXYGEN SENSOR (HO2S) MONITOR»(ref-235203-S14115958852006061500000) . The catalyst monitor algorithm is index ratio designed. This means in order to assess catalyst oxygen storage, the catalyst monitor counts precatalyst HO2S11 switches during part-throttle, closed loop fuel conditions after the engine is warmed up and the inferred catalyst temperature is within limits. The HO2S11 switches are accumulated in up to 3 different air mass regions or cells. While catalyst monitoring entry conditions are being met, the pre and post catalyst HO2S signal lengths are continually being calculated. When the required number of precatalyst HO2S11 switches has accumulated in each cell, the total signal length of the post catalyst HO2S12 is divided by the total signal length of the HO2S11 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. Typical Index Ratio Monitor Entry Conditions: Minimum 330 seconds since start-up at 21°C (70°F) Engine coolant temperature is between 76.6°C -110°C (170°F - 230°F) Intake air temperature is between -7°C - 82°C (20°F - 180°F) Time since entering close loop is 30 seconds Inferred post catalyst HO2S sensor temperature of 482°C (900 °F) EGR is between 1% and 12% Part throttle, maximum rate of change 0.2 volts/0.05 sec Vehicle speed is between 8 and 112 km/h (5 and 70 mph) Fuel level greater than 15% First Air Flow Cell Engine RPM 1,000 to 1,300 Engine load 15% to 35% Inferred catalyst temperature 454 °C - 649 °C (850 °F -1,200°F) Number of front HO2S switches: 50 Second Air Flow Cell Engine RPM 1,200 to 1,500 Engine load 20% to 35% Inferred catalyst temperature 482 °C - 677°C (900 °F -1,250°F) Number of front HO2S switches: 70 Third Air Flow Cell Engine RPM 1,300 to 1,600 Engine load 20% to 40% Inferred catalyst temperature 510 °C - 704 °C (950 °F - 1,300 °F) Number of front HO2S switches: 30
2. The DTC associated with this test is DTC P0420. Because an exponentially weighted moving average algorithm is used for malfunction determination, up to 6 drive cycles may be required to illuminate the MIL during normal driving. If the keep alive memory (KAM) is reset or the battery is disconnected, a malfunction illuminates the MIL in 2 drive cycles.

Misfire Monitor Operation

The low data rate (LDR) misfire monitoring system is capable of meeting the federal test procedure monitoring requirements and the full range of misfire monitoring requirements on 4 cylinder engines. The monitor allows for detection of any misfires that occur 6 engine revolutions after initially cranking the engine.

Overview

The EEC system provides optimum control of the engine through the enhanced capability of the powertrain control module (PCM). The EEC system also has an on board diagnostics (OBD) monitoring system with features and functions to meet federal regulations on exhaust emissions.

The EEC system has 2 major divisions: hardware and software. The hardware includes the PCM, sensors, switches, actuators, solenoids, and interconnecting terminals. The software in the PCM provides the strategy control for outputs (engine hardware) based on the values of the inputs to the PCM. EEC hardware and software are described in this article.

This article contains detailed descriptions of the operation of EEC system input sensors and switches, output actuators, solenoids, relays and connector pins (including other power ground signals).

The PCM receives information from a variety of sensor and switch inputs. Based on the strategy and calibration stored within PCM, the PCM generates the appropriate output. The system is designed to minimize emissions and optimize fuel economy and driveability. The software strategy controls the basic operation of the engine, and provides the OBD strategy, controls the malfunction indicator lamp (MIL), communicates to the diagnostic tool over the data link connector (DLC), allows for flash electrically erasable programmable read only memory (EEPROM), provides idle air and fuel trim, and controls failure mode effects management (FMEM).

Vehicle Speed Functional Overview

The Escape Hybrid has 3 methods of calculating a vehicle speed.

Powertrain Control Module (PCM) Hardware Limited Operation Strategy (HLOS)

This system of special circuitry provides minimal engine operation should the PCM, mainly the central processing unit (CPU) or EEPROM, stop functioning correctly. All modes of self-test are not functional at this time. The electronic hardware is in control of the system while in HLOS.

HLOS Allowable Output Functions

1. Spark output controlled directly by the CKP signal.
2. Fixed fuel pulse width synchronized with the CKP signal.
3. Fuel pump relay energized.

PCM Location

The PCM is located behind the instrument panel (cowl), center to both driver and passenger sides (access from the engine compartment).

The TR sensor communicates the gear selector position that the driver selects to the PCM. The PCM determines a gear mode based on the TR input and the vehicle speed signal. The PCM then broadcasts a gear mode message over the communication link. The transmission control module (TCM) uses the gear mode message to engage the transaxle in the gear that the driver selected. The other control modules use the gear mode message to control the rear lamps or a brake shift interlock solenoid. The TR sensor is mounted at the base of the gear selector assembly and the sensor shaft is moved by the selector.

Scheme 128

The Escape Hybrid is a full hybrid electric vehicle which consists of 3 key subsystems: the internal combustion engine, the electronically controlled continuously variable transaxle (CVT), and the high voltage traction battery. Refer to HYBRID ELECTRIC CONTROL HARDWARE for a detailed description of each component. In this powertrain configuration, there are 2 power sources that are connected to the driveline: a combination of the engine and the generator which uses a planetary gear set to connect to each other, and the electric traction motor which is connected to the drive wheels.

The high voltage traction battery is an electric energy storage device. The electric energy is used by the generator motor and the traction motor.

Scheme 129

The planetary gear set functions as an electronically controlled continuously variable transaxle (CVT) between the carrier gear (engine) and the ring gear (traction motor) which is connected to the drive wheels. This is achieved by controlling the sun gear (generator) speed and direction. The reason this is an CVT is due to the property of the planetary gear set in which the torque relationships between the sun gear, the carrier gear, and ring gear are fixed for this mechanical design. Therefore, the planetary gear set can also be viewed as a device that splits the engine output power to the driveline and to the generator motor. There are 2 paths for the engine to deliver its output power: from the engine to the carrier gear, to the ring gear, to the intermediate shaft (mechanical path) and from the engine to the carrier, to the sun gear, to the ring gear and to the intermediate shaft (electrical path). The combination of the mechanical and the electrical paths makes this powertrain similar to a conventional vehicle powertrain with a CVT.

The electric traction motor uses power supplied by the high voltage traction battery and provides propulsion to the vehicle independently from the engine. Both power sources, a combination of the engine and the generator and the electric traction motor, can propel the vehicle simultaneously and independently.

This powertrain configuration is able to achieve better than conventional powertrain fuel economy and lower emissions levels because

1. the engine operates in its most efficient operating regions whenever possible.
2. the engine size can be reduced with the same vehicle performance because of the dual power sources.
3. the engine operation can be better optimized since it can be stopped if operational conditions are not favorable to the fuel economy or emissions.
4. the kinetic energy during braking can be captured and stored in the high voltage traction battery through regenerative braking.

The torque determination and energy management strategy controls and operates the powertrain system to satisfy driver demands, increase the fuel economy, and decrease emissions levels.

In order to achieve better fuel economy and lower emission levels, the powertrain control module (PCM) torque determination and energy management strategy operates the powertrain system with specified operational conditions. First the torque determination and energy management strategy determines in real time how much torque the driver is requesting and how much torque each power source can deliver to the drivetrain. Then it chooses the most efficient power source for that operational condition. Some of the inputs to the energy management strategy include driver demand, traction battery state of charge, performance limitations of components, battery life (charging and discharging rate and cycling), driveability, ambient temperature, and barometric pressure.

The hybrid electric system is a torque based system. When the gear selector is placed in DRIVE, the driver is going to request a positive torque by pressing the accelerator pedal or a negative torque by pressing the brake pedal. The positive torque is perceived as vehicle acceleration, and the negative torque as vehicle deceleration (braking).

The brake and the electric power assist steering systems remain fully functional when the engine is stopped by the PCM. That allows the driver to operate the vehicle in electric mode when the engine is off.

The ignition system is designed to ignite the compressed air/fuel mixture in an internal combustion engine by a high voltage spark from an ignition coil. The ignition system also provides engine timing information to the PCM for proper vehicle operation and misfire detection.

The fuel system supplies the sequential multi-port fuel injection (SFI) fuel injectors with clean fuel at a controlled pressure. The powertrain control module (PCM) controls the fuel pump and monitors the fuel pump monitor (FPM) circuit. The PCM controls the fuel injector on/off cycle duration and determines the correct timing and amount of fuel delivered. If the injectors have been replaced it is necessary to clear the learned values contained in the keep alive memory (KAM) in the PCM. For more information, refer to RESETTING THE KEEP ALIVE MEMORY (KAM) .

The EGR system controls oxides of nitrogen (NOx) emissions. Small amounts of exhaust gases are recirculated back into the combustion chamber to mix with the air/fuel charge. The combustion chamber temperature is thereby reduced, lowering NOx emissions.

The EEGR system consists of an electric motor/EGR valve integrated assembly, the powertrain control module (PCM), and the connecting wiring. Additionally a MAP sensor is also required. Operation of the system is as follows

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

The EVAP system prevents fuel vapor build-up in the sealed fuel tank. Fuel vapors trapped in the sealed tank are vented through the vapor valve assembly on top of the tank. The vapors leave the valve assembly through a single vapor line and continue to the EVAP canister for storage until the vapors are purged to the engine for burning.

The intake air system provides clean air to the engine, optimizes air flow, and reduces unwanted induction noise. The intake air system consists of an air cleaner assembly, resonator assemblies, hydrocarbon filter and hoses. The hydrocarbon filter trap helps reduce emissions by preventing fuel vapor from escaping into the atmosphere from the intake when the engine is off. It is typically located inside the air intake system. The main component of the intake air system is the air cleaner assembly. The air cleaner assembly houses the air cleaner element that removes potential engine contaminants, particularly abrasives. The mass air flow (MAF) sensor is attached externally to the air cleaner assembly and measures the quantity of air delivered to the engine combustion chamber. The MAF sensor can be replaced as an individual component. The intake air system also contains a intake air temperature (IAT) sensor, which is integrated with the MAF sensor. Refer to POWERTRAIN CONTROL MODULE (PCM) INPUTS for additional information on the MAF and IAT sensors. The air induction resonator is a part of the intake air housing. The function of a resonator is to reduce induction noise. The air induction components are connected to each other and to the electronic throttle body assembly with hoses.

Note. For illustrations of intake air system components, refer to INTAKE AIR DISTRIBUTION & FILTERING - HYBRID .

The overall quantity of air metered to the engine is controlled by the TORQUE BASED ELECTRONIC THROTTLE CONTROL (ETC) system.

The PCV system cycles crankcase gases back through the induction system into the engine where they are burned. The PCV valve regulates the amount of ventilated air and blow-by gases to the intake manifold.

The Escape Hybrid uses a non-heated PCV system. PCV systems that comply with OBD PCV monitoring requirements will use a quarter-turn camlock thread design at one end to prevent accidental disconnection from the valve cover. For more information about the PCV monitor refer to POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM MONITOR .

Scheme 130

The catalytic converter and exhaust systems work together to control the release of harmful engine exhaust emissions into the atmosphere. The engine exhaust gas consists mainly of nitrogen (N), carbon dioxide (CO2) and water vapor (H 2 O). However, it also contains carbon monoxide (CO), oxides of nitrogen (NO x), hydrogen (H), and various unburned hydrocarbons (HCs). CO, NO x, and HCs are major air pollutants, and their emission into the atmosphere must be controlled.

The exhaust system generally consists of an exhaust manifold, front exhaust pipe, front heated oxygen sensor (HO2S), rear exhaust pipe, rear HO2S, a muffler and an exhaust tailpipe. The catalytic converter is installed between the front and rear exhaust pipes. Catalytic converter efficiency is monitored by the on board diagnostic (OBD) system strategy in the PCM. Refer to CATALYST EFFICIENCY MONITOR for specific OBD catalyst monitor information.

The number of HO2S used in the exhaust stream and the location of these sensors depend on the vehicle emission certification level (LEV, ULEV, PZEV). The Escape Hybrid is a partial zero emission vehicle (PZEV) but only 2 out of 3 HO2S sensors provide input to the powertrain control module (PCM). The first sensor in the exhaust stream before the catalyst (HO2S11) is used for primary fuel control and the last sensor after the catalyst (HO2S12) is used to monitor the light-off catalyst. The middle sensor in the exhaust stream does not provide any input to the PCM.

Scheme 131

The Generation II (Gen II) torque based electronic throttle control (ETC) is a hardware and software strategy that delivers an engine output torque (through throttle angle) based on driver demand (pedal position). It uses an electronic throttle body, the PCM, and an accelerator pedal assembly to the control throttle opening and engine torque. The ETC system basically replaces the standard cable operated accelerator pedal, idle air control (IAC) valve, 3-wire throttle position (TP) sensor, and mechanical throttle body.