Engine Controls - Description and Operation (Except Diesel & Hybrid): Overview Mercury Sable V

Overview

The EEC system provides optimum control of the engine and transmission 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.

Some vehicle applications use a stand-alone transmission control module (TCM). Even though it is still part of the EEC system, the TCM communicates with the PCM, the antilock brake system (ABS) module, the instrument cluster, and the four-wheel drive (4WD) control modules using the high speed controller area network (CAN) communications network. The TCM incorporates a stand alone OBD-II system. The TCM independently processes and stores diagnostic trouble codes (DTCs), freeze frame, support PIDs as well as J1979 Mode 09 CALID and calibration verification number. The TCM does not directly illuminate the malfunction indicator lamp (MIL), but requests the PCM to do so. The TCM is located inside the transmission assembly. It is not repairable, with the exception of reprogramming.

Below is a list of transmissions that use a TCM

1. AWF21 (FWD) 6-speed automatic transmission
2. FNR5 (FWD) transmission
3. F21 (FWD) transmission
4. ZF CFT30 (FWD) continuously variable transmission (CVT)
5. ZF 6HP26 (RWD) transmission
6. ZF 6R (RWD)
7. 6R60 (RWD)

For additional information on these transmissions and TCM diagnostics, refer to the AUTOMATIC TRANSAXLE/TRANSMISSION - 4R70E/4R75E -- E-SERIES.

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. The EEC hardware and software are discussed.

This part contains detailed descriptions of the operation of the EEC system input sensors and switches, output actuators, solenoids, relays and connector pins (including other power-ground signals). For additional information on the input sensors and output actuators, refer to ENGINE CONTROL COMPONENTS.

The PCM receives information from a variety of sensor and switch inputs. Based on the strategy and calibration stored within the memory chip, 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 transmission, provides the OBD strategy, controls the MIL, communicates to the scan tool via 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 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 service, and at the assembly plant. The ISO 14229 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).

For the 2008 model year, the new ISO 14229 standard is standard on the Focus powertrain control module (PCM). The ISO 14229 changes the way PIDs, DTCs, and output state control is processed internally in the PCM and in the scan tool software. Most of the changes are to 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.

DTC Structure - Like all digital signals, DTCs are sent to the scan tool as a series of 1s and 0s. Each DTC is made up of 2 data bytes which each consist of 8 bits that can be set to 1 or 0. The data is decoded by the scan tool to display each set of 4 bits as a hexadecimal number (0 to F) in order to display the DTCs in the conventional format. For example, P0420 - Catalyst System Efficiency Below Threshold (Bank 1).

The table below shows how to decode the bits into hex digits.

The first 4 bits of a DTC do not convert directly into hex digits. The conversion into different types of DTCs (P, B, C and U) is defined by SAE J2012. This standard contains DTC definitions and formats.

ISO 14229 sends 2 additional bytes of information with each DTC, a failure type byte and a status byte.

All ISO 14229 DTCs are 4 bytes long instead of 3 bytes or 2 bytes long. Additionally, the status byte for ISO 14229 DTCs is defined differently than the status byte for previous applications with 3 byte DTCs.

Failure Type Byte - The failure type byte is designed to describe the specific failure associated with the basic DTC. For example, an 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 sensor circuit voltage out of range. The base DTC, P0110, means intake air temperature sensor circuit, while the failure type byte 1C means circuit voltage out of range. This DTC structure was designed to allow manufacturers to more precisely identify different kinds of faults without always having to define new DTC numbers.

The PCM does not use failure type bytes and always sends a failure type byte of 00 (no sub type information). This is because OBD-II regulations require manufacturers to use 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 bit and is the left-most bit while bit 0 is the least significant bit and is the right-most bit.

DTC Status Bit Definitions - Refer to the following status bit descriptions

Bit 7

1. 0 - The ECU is not requesting warning indicator to be active
2. 1 - The ECU is requesting warning indicator to be active

Bit 6

1. 0 - The DTC test completed this monitoring cycle
2. 1 - The DTC test has not completed this monitoring cycle

Bit 5

1. 0 - The DTC test never failed since last code clear
2. 1 - The DTC test failed at least once since last code clear

Bit 4

1. 0 - The DTC test completed since the last code clear
2. 1 - The DTC test not completed since the last code clear

Bit 3

1. 0 - The DTC is not confirmed at the time of the request
2. 1 - The DTC is confirmed at the time of the request

Bit 2

1. 0 - The DTC was not failed on the current or previous monitoring cycle
2. 1 - The DTC failed on the current or previous monitoring cycle

Bit 1

1. 0 - The DTC never failed on the current monitoring cycle
2. 1 - The DTC failed on the current monitoring cycle

Bit 0

1. 0 - The DTC is not failed at the time of request
2. 1 - The DTC is failed at the time of request

For DTCs that illuminate the MIL, a confirmed DTC means the PCM has stored a DTC and has illuminated the MIL. If the fault has corrected itself, the MIL may no longer be illuminated but the DTC still shows a confirmed status for 40 warm up cycles at which time the DTC is erased. Bit 7 can be used to determine if the MIL is illuminated for the DTC.

For DTCs that do not illuminate the MIL, a confirmed DTC means the PCM has stored a DTC. If the fault has corrected itself, the DTC still shows a confirmed status for 40 warm up cycles at which time the DTC is erased.

To determine if a test has completed and passed, for example, after a repair, information can be combined from 2 bits as follows

If bit 6 is 0 (the DTC test completed this monitoring cycle), and bit 1 is 0 (the DTC never failed on the current monitoring cycle), then the DTC has been evaluated at least once this drive cycle and was a pass.

If bit 6 is 0 (the DTC test completed this monitoring cycle) and bit 0 is 0 (the DTC is not failed at the time of request), then the most recent test result for that DTC was a pass.

The status byte bits can be decoded as a 2 digit hexadecimal number, and can be displayed as the last 2 digits of the DTC, for example for DTC P0110:1C-AF, AF represents the status byte info.

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 heated oxygen sensor (HO2S), rear exhaust pipe, catalyst HO2S, a muffler, and an exhaust tailpipe. The catalytic converter is typically installed between the front and rear exhaust pipes. On some vehicle applications, more than one catalyst is used between the front and rear exhaust pipes. Catalytic converter efficiency is monitored by the on board diagnostic (OBD) system strategy in the powertrain control module (PCM). For information on the OBD catalyst monitor, refer to the description for the CATALYST EFFICIENCY MONITOR.

For most vehicles, only 2 HO2Ss are used in an exhaust stream. The front sensors (HO2S11/HO2S21) before the catalyst are used for primary fuel control while the ones after the catalyst (HO2S12/HO2S22) are used to monitor catalyst efficiency. However, some partial zero emission vehicles (PZEV) use 3 HO2Ss for each engine bank. The stream 1 sensors (HO2S11/HO2S21) located before the catalyst are used for primary fuel control, the stream 2 sensors (HO2S12/HO2S22) are used to monitor the light-off catalyst, and the stream 3 sensors (HO2S13/HO2S23) located after the catalyst are used for long term fuel trim control to optimize catalyst efficiency (fore aft oxygen sensor control).

Scheme 1

Scheme 2

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.

All applications required to meet on board diagnostics (OBD) regulations use the enhanced EVAP system. Some applications also incorporate an on-board refueling vapor recovery (ORVR) system. Refer to the EVAPORATIVE EMISSIONS -- E-SERIES for vehicle specific information on the description and operation of the evaporative emissions system.

The EGR system controls the oxides of nitrogen (NO x ) 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 reduced, lowering NO x emissions.

The fuel system supplies the sequential multiport 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 circuit. The PCM controls the fuel injector on/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. Refer to RESETTING THE KEEP ALIVE MEMORY (KAM).

The 2 types of fuel systems used are

1. electronic returnless fuel
2. mechanical returnless fuel

The ignition system is designed to ignite the compressed air/fuel mixture in an internal combustion engine by a high voltage spark delivered from an ignition coil controlled by the powertrain control module (PCM).

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, and hoses. Some vehicles use a hydrocarbon filter trap to help 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 mass air flow (MAF) sensor is attached to the air cleaner assembly and measures the volume of air delivered to the engine. The hydrocarbon trap is part of the EVAP system. For more information on the EVAP system, refer to EVAPORATIVE EMISSION (EVAP) SYSTEMS. The MAF sensor can be replaced as an individual component. The intake air system also contains a sensor that measures the intake air temperature (IAT), which is also integrated with the MAF sensor. For additional information on the intake air system components, refer to ENGINE CONTROL COMPONENTS. Intake air components can be separate components or part of the intake air housing. The function of a resonator is to reduce induction noise. The intake air components are connected to each other and to the throttle body assembly with hoses.

Scheme 3

Throttle Body System Overview

Note. This overview is for applications without electronic throttle control (ETC). For ETC applications, refer to TORQUE BASED ELECTRONIC THROTTLE CONTROL (ETC).

Note. The traditional idle air adjust procedure and the throttle return screw are no longer used on OBD applications.

The throttle body system meters air to the engine during idle, part throttle, and wide open throttle (WOT) conditions. The throttle body system consists of an idle air control (IAC) valve assembly, an idle air orifice, single or dual bores with butterfly valve throttle plates, and a throttle position (TP) sensor. One other source of idle air flow is the positive crankcase ventilation (PCV) system. The combined idle air flow (from idle air orifice IAC flow and PCV flow) is measured by the MAF sensor on all applications.

During idle, the throttle body assembly provides a set amount of air flow to the engine through the idle air passage and the PCV valve. The IAC valve assembly provides additional air when commanded by the powertrain control module (PCM) to maintain the correct engine idle speed under varying conditions. The IAC valve assembly mounts directly to the intake manifold assembly in most applications. Idle speed is controlled by the PCM and cannot be adjusted.

Throttle rotation is controlled by a cam/cable linkage to slow the initial opening rate of the throttle plate. The TP sensor monitors the throttle position and provides a signal to the PCM. Some throttle body applications provide an air supply channel upstream of the throttle plate to provide fresh air to the PCV or IAC systems. Other throttle body applications provide individual vacuum taps downstream of the throttle plate for PCV return, exhaust gas recirculation (EGR), evaporative emission (EVAP), and miscellaneous control signals.

Throttle Body System Hardware - The major components of the throttle body assembly include the TP sensor, the IAC valve assembly, and the throttle body housing assembly. For additional information on the intake air system components, refer to ENGINE CONTROL COMPONENTS.

Throttle Body Housing - The throttle body housing assembly is a single piece aluminum or plastic casting with an air passage and a butterfly throttle plate with linkage mechanisms. When the throttle plate is in the idle (or closed) position, the throttle lever arm should be in contact with the throttle return stop. The throttle return stop prevents the throttle plate from contacting the bore and sticking closed. The setting also establishes the amount of air flow between the throttle plate and bore. To minimize the closed plate air flow, a special coating is applied to the throttle plate and bore to help seal this area. This sealant/coating also makes the throttle body resistant to engine intake sludge accumulation.

Overview of the Intake Manifold Runner Control (IMRC) and Intake Manifold Tuning Valve (IMTV) Systems

There are 3 basic types of intake air sub-systems

1. IMRC electric actuated system
2. IMRC vacuum actuated system
3. IMTV

There are several different styles of hardware used to control airflow within the engine air intake system. In general, the devices are defined based on whether they control in-cylinder motion (charge motion) or manifold dynamics (tuning).

The IMRC is a charge motion device that modifies the air charge motion in the manifold. The IMRC control valve is located close to the intake valve/cylinder head. The IMRC actuator can be either electric or vacuum controlled. The IMRC system must have a monitor feedback system in order to meet OBD-II regulations.

The IMTV is a manifold tuning device that effects the air flow volume of the manifold by connecting multiple plenums or inlets within the manifold system. The IMTV control valve is located in the center of the intake manifold away from the intake valve or cylinder head. The IMTV actuator can be either electric or vacuum controlled. The IMTV system does not have to be monitored for OBD-II regulations.

Some vehicles may use both systems.

These subsystems are used to provide increased intake airflow to improve torque, emissions and performance. The overall volume of air metered to the engine is controlled by the throttle body. Vehicles equipped with electronic throttle control (ETC) do not use idle air control (IAC).

The PCV system cycles crankcase gases back through the intake air 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.

Currently, both heated and non-heated PCV systems are used. The heated systems use either a water heated valve, an electrically heated valve, or an electrically heated tube. Engine coolant flows around the water heated valve to prevent it from freezing. Electrically heated systems use a heating element enclosed in the PCV valve, PCV fitting or the PCV tube to prevent the valve or tube from freezing. The valve or the tube heater can be controlled by either the powertrain control module (PCM) or the thermal harness.

1. Thermal harness controlled heater - On vehicle applications that are equipped with a thermal harness to the PCV valve or tube. The thermal harness only provides electrical continuity to the heating element when temperatures are less than 5°C +/- 4°C (40°F +/- 7°F). Typically this harness is located close to the PCV valve or tube.
2. PCM controlled heater - On these applications the PCV heater is turned on by the PCM. When the intake air temperature is less than 0°C (32°F) the PCM grounds the positive crankcase ventilation valve heater control (PCVHC) circuit and turns the heater ON. When the intake air temperature exceeds 9°C (48°F) the heater is turned OFF. The PCV heater is also OFF when the engine is not running to prevent unnecessary battery drain. The heater is also OFF if the vehicle charging system is greater than 16 volts. This minimizes heater element overload.

PCV systems that comply with OBD PCV monitoring requirements use a quarter-turn cam-lock 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.

Note. When the battery (or PCM) is disconnected and connected, some abnormal drive symptoms may occur while the vehicle relearns its adaptive strategy. The charging system set point may also vary. The vehicle may need to be driven to relearn its strategy.

The PCM-controlled charging system provides many additional benefits over the current integral generator regulator system. The first benefit is improved battery life. In a PCM-controlled charging system, the regulator voltage set point is determined by the PCM and communicated to the regulator through the generator regulator control (GENRC) circuit. The PCM uses an algorithm to estimate battery temperature. Improving battery temperature estimates reduces battery damage caused by over- and undercharging.

The second benefit is improved engine performance. Whenever the PCM senses a wide open throttle (WOT) condition, the PCM momentarily lowers the regulator voltage set point. This reduces the torque load of the generator on the engine and improves acceleration. The PCM has a calibratable time limit on this reduced voltage feature. This is to prevent the generator output from being cut back for an extended WOT period, which could cause battery discharge.

The third benefit is improved idle stability. In response to the PCM GENRC signal, the regulator uses a generator load input (GENLI) signal to provide feedback to the PCM. The GENLI signal provides the PCM with charging system information. Specifically, it lets the PCM know when the charging system receives a transient electrical load which would normally affect idle stability. Because the PCM can anticipate additional loads, actions can be taken to minimize idle sag. The PCM can choose to either reduce the regulator set point or increase engine idle speed, both of which are calibratable features. In order to establish whether the regulator is accurately maintaining the desired voltage set point, the regulator uses a charging system voltage line to sense battery voltage.

The fourth benefit is reduced cranking efforts. The PCM can reduce the mechanical load on the starter by initially commanding a low voltage set point. This may improve start times.

If the PCM detects a charging system error, it broadcasts a low voltage telltale (ON) network communication message which tells the cluster to illuminate the charge indicator. The charge indicator is illuminated if the PCM does not see a signal on the GENLI circuit for a time period greater than 500 milliseconds. This telltale command is also used to indicate over-voltage conditions detected by the PCM-controlled generator.

Each time the ignition switch is cycled to the run position, the instrument cluster initiates a bulb check by illuminating the charge indicator. It is the responsibility of the PCM to issue a low voltage telltale (OFF) command if the charging system is functioning correctly. This message should be sent during the network initialization in the voluntary phase (250 milliseconds to 450 milliseconds after the ignition switch is cycled to the run position). If a low voltage telltale (OFF) communications network message is not received, the instrument cluster continues to illuminate the charge indicator indefinitely.

The secondary AIR system controls emissions during the first few seconds of engine operation by forcing air downstream into the exhaust manifolds to oxidize the hydrocarbons and carbon monoxide created by running rich at start up.

The torque based ETC is a hardware and software strategy that delivers an engine output torque (via throttle angle) based on driver demand (pedal position). It uses an electronic throttle body, the powertrain control module (PCM), and an accelerator pedal assembly to control the throttle opening and engine torque.

Torque based ETC enables aggressive automatic transmission shift schedules (earlier upshifts and later downshifts). This is possible by adjusting the throttle angle to achieve the same wheel torque during shifts, and by calculating this desired torque, the system prevents engine lugging (low RPM and low manifold vacuum) while still delivering the performance and torque requested by the driver. It also enables many fuel economy/emission improvement technologies such as variable camshaft timing (VCT) (deliver same torque during transitions).

Torque based ETC also results in less intrusive vehicle and engine speed limiting, along with smoother traction control.

Other benefits of ETC are

1. eliminate cruise control actuators
2. eliminate idle air control (IAC) valve
3. better airflow range
4. packaging (no cable)
5. more responsive powertrain at altitude and improved shift quality

The ETC system illuminates a powertrain malfunction indicator (wrench) on the instrument cluster when a concern is present. Concerns are accompanied by diagnostic trouble codes (DTCs) and may also illuminate the malfunction indicator lamp (MIL).

The VCT enables rotation of the camshaft(s) relative to the crankshaft rotation as a function of engine operating conditions. There are 4 types of VCT systems.

1. Exhaust phase shifting (EPS) system - the exhaust cam is the active cam being retarded.
2. Intake phase shifting (IPS) system - the intake cam is the active cam being advanced.
3. Dual equal phase shifting (DEPS) system - both intake and exhaust cams are phase shifted and equally advanced or retarded.
4. Dual independent phase shifting (DIPS) system - where both the intake and exhaust cams are shifted independently.

All systems have 4 operational modes: idle, part throttle, wide open throttle (WOT), and default mode. At idle and low engine speeds with closed throttle, the powertrain control module (PCM) determines the phase angle based on air flow, engine oil temperature and engine coolant temperature. 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. IPS systems also have the added benefit of improved torque. In addition, some VCT system applications can eliminate the need for an external exhaust gas recirculation (EGR) system. The elimination of the EGR system is accomplished by controlling the overlap time between the intake valve opening and exhaust valve closing. Currently, both the IPS and DEPS systems are used.

OBD-I, OBD-II and Engine Manufacturer Diagnostics (EMD) Overview

The California Air Resources Board (CARB) began regulating OBD systems for vehicles sold in California beginning with the 1988 model year. The initial requirements, known as OBD-I, required identifying the likely area of malfunction with regard to the fuel metering system, exhaust gas recirculation (EGR) system, emission-related components and the powertrain control module (PCM). A malfunction indicator lamp (MIL) was required to illuminate and alert the driver of the malfunction and the need to repair the emission control system. A diagnostic trouble code (DTC) was required to assist in identifying the system or component associated with the malfunction.

Starting with the 1994 model year, both CARB and the Environmental Protection Agency (EPA) mandated enhanced OBD systems, commonly known as OBD-II. The objectives of the OBD-II system are to improve air quality by reducing high in-use 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.

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, malfunctions 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 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 PCM keep alive memory (KAM) when a malfunction is initially detected. Pending DTCs are displayed as long as the malfunction is present. Note that OBD regulations required a complete malfunction-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 malfunction-free monitoring cycle. 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, 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 KAM at the point the malfunction 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 malfunction 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 malfunction is detected. This data is accessible with the scan tool to allow duplicating the conditions when the malfunction 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 stores a DTC P1000 and blinks the MIL after 15 seconds of key-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 IM readiness indicators must show that all monitors have been completed prior to the OBD check.

OBD-II was required on all California and California State gasoline engine vehicles up to 14,000 lbs. Gross vehicle weight rating (GVWR) starting in the 1996 MY and all diesel engine vehicles up to 14,000 lbs. GVWR starting in the 1997 MY.

California States are ones that have adopted California emission regulations, starting in the 1998 MY. For example, Massachusetts, New York, Vermont and Maine have adopted California's emission regulations. These States receive California-certified vehicles for passenger cars and light trucks, and medium-duty vehicles, up to 14,000 lbs GVWR.

OBD-II was also required on all Federal gasoline engine vehicles up to 8,500 lbs. GVWR starting in the 1996 MY and all diesel engine vehicles up to 8,500 lbs. GVWR starting in the 1997 MY.

Starting in the 2004 MY, Federal vehicle over 8,500 lbs. were required to phase in OBD-II. By the 2006 MY, all of Ford's Federal vehicles from 8,500 to 14,000 lbs GVWR have been phased into OBD-II and OBD-I systems are no longer utilized in vehicles up to 14,000 lbs GVWR.

EMD Systems - EMD was required on all 2007 MY and beyond California gasoline-fueled 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 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 PM 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.

EMD vehicles use that 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), fuel tank pressure sensor, canister vent solenoid, and a different PCM calibration.

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 comprehension of the monitor and associated DTCs.

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

Scheme 4

General Catalyst Monitor Operation

Monitor execution is once per drive cycle. The typical monitor duration is 700 seconds or 10-20 seconds for the universal HO2S. In order for the catalyst monitor to run, the HO2S monitor must be complete and the secondary AIR and EVAP system functional with no stored DTCs. 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.

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 1 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.

Most 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 that the catalyst nearest the engine deteriorate first, allowing the catalyst monitor to be more sensitive and illuminate the MIL correctly at lower emission standards.

Most 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 3-can per bank system. (A few applications placed the HO2S in the middle of the catalyst can, between the first and second bricks).

Some partial zero emission vehicles (PZEV) use 3 HO2S per engine bank. The front sensors or stream 1 (HO2S11/HO2S21) are the primary fuel control sensors. The next sensors downstream or stream 2 in the exhaust are used to monitor the light-off catalyst (HO2S12/HO2S22). The last sensors downstream or stream 3 in the exhaust (HO2S13/HO2S23) are used for very long term fuel trim in order to optimize catalyst efficiency (fore aft oxygen sensor control). For additional heated oxygen sensor 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.

Scheme 5

The cold start emission reduction monitor is an on-board strategy designed for vehicles that meet the low emissions vehicle-II (LEV-II) emissions standards. The monitor works by validating the operation of the components of the system required to achieve the cold start emission reduction strategy. There are 2 types of monitors

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

See also:
• DIAGNOSTIC TROUBLE CODE (DTC) CHARTS AND DESCRIPTIONS