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

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 diagnostic (OBD) monitoring system with features and functions to meet federal regulations on exhaust emissions.

The EEC system has two 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 the 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, provides the OBD strategy, controls the malfunction indicator lamp (MIL), communicates to the scan 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).

International Standards Organization (ISO) 14229 Diagnostic Trouble Code (DTC) Descriptions

The ISO 14229 protocol is a global, diagnostic communication standard. The ISO 14229 is a set of standard diagnostic messages that can be used to diagnose any vehicle module in use and at the assembly plant. The ISO 14229 protocol is similar to the Society of Automotive Engineers (SAE) J2190 diagnostic communication standard that was used by all original equipment manufacturers (OEMs) for previous communication protocols, like J1850 standard corporate protocol (SCP).

The ISO 14229 protocol changes the way PIDs, DTCs, and output state control (OSC) is processed internally in the PCM and in the scan tool software. Most of the changes make data transfer between electronic modules more efficient, and the amount and type of information that is available for each DTC. This information may be helpful in diagnosing driveability concerns.

Vehicle Speed Functional Overview

The hybrid vehicle uses three methods to calculate vehicle speed. The PCM uses the ABS signal if available, and will substitute the motor speed if the ABS signal is missing. The PCM will use the engine and generator speed calculation if both the ABS and motor speeds are unavailable.

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 (CO 2 ) 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). The major air pollutants of CO, NO x , and HCs, and their emission into the atmosphere must be controlled.

The exhaust system generally consists of an exhaust manifold, front exhaust pipe, front universal 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. For specific OBD catalyst monitor information, refer to the CATALYST EFFICIENCY MONITOR .

The hybrid vehicle is a partial zero emission vehicle (PZEV) equipped with two sensors that provide input to the PCM. The first sensor in the exhaust stream before the catalyst is the universal HO2S and is used for primary fuel control. The second sensor in the exhaust stream after the catalyst is the HO2S and is used to monitor the light off catalyst.

Scheme 1

The EVAP system prevents fuel vapor build up in the fuel tank. Fuel vapors trapped in the 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.

The EGR system controls the nitrogen oxides (NO x ) emissions. Small amounts of exhaust gases are recirculated back into the combustion chamber to mix with the air to fuel charge. The combustion chamber temperature is reduced, lowering NO x emissions.

The fuel system supplies the fuel injectors with clean fuel at a controlled pressure. The powertrain control module (PCM) controls the fuel pump and monitors the fuel pump circuit. The PCM controls the fuel injector ON and OFF cycle duration and determines the correct timing and amount of fuel delivered. When a new fuel injector is installed it is necessary to reset 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 hybrid electric system consists of four key components: the internal combustion engine, the TCM, the transmission, and the high voltage traction battery. For a detailed description of each component, refer to HYBRID ELECTRIC CONTROL HARDWARE . In this powertrain configuration, there are two 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 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.

Hybrid Electric System

Scheme 2

The planetary gear set functions as an electronically controlled transmission 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 electronically controlled transmission 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 two 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.

The electric traction motor uses voltage supplied by the high voltage traction battery and provides propulsion to the vehicle independently from the engine. 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 optimal fuel economy and lower emissions levels because

1. the engine operates in its most efficient operating modes 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 the powertrain system to the driver demands, increase the fuel economy, and decrease emissions levels.

In order to achieve optimum fuel economy and lower emission levels, the TCM torque determination and energy management strategy controls the powertrain system with specified operational conditions. First, the torque determination and energy management strategy determines the torque the driver is requesting and the amount of torque each power source can deliver to the drivetrain. Then applies the most efficient power source for that operational condition. Some of the inputs to the energy management strategy include driver demand, high voltage traction battery state of charge, performance limitations of components, battery life, driveability, ambient temperature, and barometric pressure.

The brake and the electric power assist steering systems remain fully functional when the engine is stopped by the PCM. This 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 and 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 powertrain control module (PCM) for correct vehicle operation and misfire detection.

The intake air system provides clean air to the engine, optimizes airflow, and reduces unwanted induction noise. The intake air system consists of an air cleaner assembly, resonator assemblies and hoses. 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 airflow (MAF) sensor is attached externally to the air cleaner assembly and measures the quantity of air delivered to the engine. 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. For additional information, refer to ENGINE CONTROL COMPONENTS . The intake air resonator is a part of the intake air housing. The function of a resonator is to reduce intake air noise. The intake air system components are connected to each other and to the electronic throttle body assembly with hoses.

The overall quantity of air metered to the engine is controlled by the torque based electronic throttle control (ETC) system.

For additional information, refer to ELECTRONIC THROTTLE CONTROL (ETC) SYSTEM .

For illustrations of intake air system components, refer to the Intake Air Distribution and Filtering article.

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

The PCV systems that comply with on board diagnostics (OBD) PCV monitoring requirements 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 3

The ETC system is a hardware and software strategy that delivers engine output torque. The ETC system uses an electronic throttle body (ETB), the PCM, and an accelerator pedal assembly to control the throttle opening and engine torque.

The intake phase shifting (IPS) VCT system enables rotation of the intake camshaft relative to the crankshaft rotation as a function of engine operating conditions.

The VCT system has several operational modes: idle, part throttle, wide open throttle (WOT), and default mode. At idle and low engine speeds with closed throttle, the PCM determines the phase angle based on airflow, engine oil temperature and engine coolant. At part and wide open throttle the PCM determines the phase angle based on engine RPM, load, and throttle position. VCT systems provide reduced emissions and enhanced engine power, fuel economy and idle quality. The VCT system also has the added benefit of improved torque.

The VCT system knocking and noise concerns are diagnosed in the Service Information. For additional information, refer to the Engine System - General Information article. Verification of incorrect VCT phasing on a warm engine operating below 1500 RPM can be isolated using a stethoscope and by monitoring the PIDs using a scan tool. If the VCT phaser does not maintain correct valve timing, low oil pressure or oil flow restrictions are primary possible causes. Verify correct oil pressure and flow, refer to the Engine System - General Information article.

OBD Overview

The objectives of the OBD system are to improve air quality by reducing high emissions caused by emission related concerns, reducing the time between the occurrence of a concern 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 concern 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 concern.

The OBD 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-II (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 two drive cycles.

The OBD 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 powertrain control module (PCM) keep alive memory (KAM) when a concern is initially detected. Pending DTCs are displayed as long as the concern is present. Note that OBD regulations required 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 two consecutive drive cycles, the MIL is illuminated. Once the MIL is illuminated, three consecutive drive cycles without a concern 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 will be 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.

The OBD I/M readiness indicators show whether all of the OBD monitors have been completed since the last time the KAM or the PCM DTCs have been cleared. The MIL blinks 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.

The following information 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 provide only 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 this article.

Scheme 4

Catalyst Efficiency Monitor Operation

1. The hybrid vehicle exhaust system uses two separate HO2S. The front HO2S is a universal HO2S and is the primary fuel control sensor. This sensor is the first HO2S in the exhaust stream and is referred to as the front or stream 1 HO2S. The last HO2S downstream in the exhaust system is used to monitor the catalyst and is referred to as the rear or stream 2 HO2S. For additional HO2S information, refer to the «HEATED OXYGEN SENSOR (HO2S) MONITOR»(ref-608998-S12954794782014041200000) . Typical monitor entry conditions: engine coolant temperature is between 71°C - 110°C (160°F - 230°F) intake air temperature is between -7°C - 59°C (20°F - 140°F) inferred rear HO2S sensor temperature, minimum of 427°C (800°F) inferred catalyst midbed temperature is between 482°C - 815°C (900°F - 1500°F) fuel level is greater than 15% air mass is less than 15g/sec (2.0 lb/min)
2. An exponentially weighted moving average algorithm is used to determine a concern. Three DFCU events are required to illuminate the MIL during normal customer driving. If the KAM is reset, a concern illuminates the MIL in two drive cycles.

Scheme 5

The cold start emission reduction monitor works by detecting the lack of catalyst warm up resulting from a failure to apply sufficient cold start emission reduction during a cold start. There are 2 types of monitors

1. cold start emission reduction component monitor
2. cold start emission reduction system monitor

Cold Start Engine Speed Monitor Operation

Once the waiting period is complete, the monitor compares the average difference between desired and commanded spark to a calibrated threshold that is a function of the engine coolant temperature at start. If the difference exceeds the calibrated threshold, a DTC sets.

1. DTC: P050A Cold start idle air control system performance
2. Monitor execution: Once per driving cycle, during the first 15 seconds of a cold start
3. Monitor sequence: None
4. Monitoring duration: Data gathering occurs during the first 15 seconds of a cold start. The decision to set P050A is made 300 seconds after start. This delay gives time for other diagnostics (for example, misfire monitor) to determine if another DTC should set instead of P050A.

Cold Start Spark Timing Monitor Operation

Once the waiting period is complete, the monitor compares the average difference between desired and commanded spark to a calibrated threshold that is a function of the engine coolant temperature at start. If the difference exceeds the calibrated threshold, a DTC is set.

1. DTC: P050B cold start ignition timing performance
2. Monitor execution: Once per driving cycle, during the first 15 seconds of a cold start
3. Monitor sequence: None
4. Monitoring duration: Data gathering occurs during the first 15 seconds of a cold start. The decision to set P050B is made 300 seconds after start. This delay gives time for other diagnostics (for example, misfire monitor) to determine if another DTC should set instead of P050B.

Cold Start Emission Reduction System Monitor Operation

1. DTC: P050E cold start engine exhaust temperature too low
2. Monitor execution: Once per driving cycle, during the first 15 seconds of a cold start
3. Monitor sequence: None
4. Monitoring duration: Data gathering occurs during the first 15 seconds of a cold start. The decision to set P050E is made 300 seconds after start. This delay gives time for other diagnostics (for example, misfire monitor) to determine if another DTC should set instead of P050E.

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 four cylinder engines. The monitor allows for detection of any misfires that occur six engine revolutions after initially cranking the engine.