Engine Controls - Description & Operation (except Diesel & Hybrid) Ford Five Hundred I

VECI Decal

Each vehicle has a VECI decal containing emission control information that applies specifically to the vehicle and engine. The specifications on the decal are critical to repairing emissions systems.

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VECI Decal Location

Typical location of the decal will be on the underside of the hood or the radiator support sight shield.

Engine/Evaporative Emission (EVAP) System Information

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

The ENGINE FAMILY GROUP and EVAPORATIVE FAMILY name consists of 12 characters each.

Both the engine family group and the evaporative family name are listed in the box on the emission decal as indicated in the area marked as engine evaporative family information. The first line contains engine size and the 12-character engine family group. The second line contains the 12-character evaporative family name information. Both the engine family group and the evaporative family name are specific to the vehicle. Please refer to the ENGINE FAMILY GROUP WORK SHEET and the EVAPORATIVE FAMILY NAME WORK SHEET for decoding information.

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ENGINE FAMILY GROUP WORK SHEET

EVAPORATIVE FAMILY NAME WORK SHEET

Base Engine Calibration Information

Base engine calibration information, also sometimes referred to as the powertrain calibration, is located in the lower right corner of the Vehicle Certification (VC) Label. Engine calibration information is limited to a maximum of 5 characters per line (2 lines maximum). Calibration information more than 5 characters long will wrap to the second line of this field. Only the base calibration will appear on this label. For more information on the Vehicle Certification Label or Engine Calibration, refer to IDENTIFICATION CODES .

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Decal Location

Typical location of the Vehicle Certification label is on the LH door or door post pillar.

Engine Calibration Code

2005 MODEL YEAR EXAMPLE - ENGINE CALIBRATION CODE

VECI Acronym Definitions

CARB: California Air Resource Board

CARB LEV: Low Emission Vehicle

CARB TLEV: Transitional Low Emission Vehicle

CARB ULEV: Ultra Low Emission Vehicle

CARB ZEV: Zero Emission Vehicle

CI: Cylinder Injection

EPA: Environmental Protection Agency

EVAP: Evaporative Emissions

GVW: Gross Vehicle Weight

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

HHDE: Heavy Heavy Duty Engine

HHDDE: Heavy Heavy Duty Diesel Engine

MHDE: Medium Heavy Duty Diesel Engine

MPI: Multi-Port Injection

LDDT: Light Duty Diesel Truck categories

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

LDV: Light Duty Vehicle, generally passenger cars and light trucks under 6000 pounds GVWR.

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

LVW: Loaded Vehicle Weight, curb weight plus 300 pounds.

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

MDV: Medium Duty Vehicle

MHDE: Medium Heavy Duty Engine

MY: Model Year

NCP: Non-Compliance Penalty

OBD: On-Board Diagnostic

ORVR: On-Board Refueling Vapor Recovery

PC: Passenger Car

SI: Sequential Injection

SULEV: Super Ultra Low Emission Vehicle

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

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

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

LEV: Low Emission Vehicle

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

ZEV: Zero Emission Vehicle

PZEV: Partially Zero Emission Vehicle

ULEV: Ultra Low Emission Vehicle

ILEV: Inherently Low Emission Vehicle

OBD-I and OBD-II Overview

The California Air Resources Board (CARB) began regulating On-Board Diagnostic (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) labeled CHECK ENGINE or SERVICE ENGINE SOON was required to illuminate and alert the driver of the malfunction and the need to repair the emission control system. A fault code or diagnostic trouble code (DTC) was required to assist in identifying the system or component associated with the fault.

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.

North American OBD-II/Federal OBD requirements apply to

1. Gasoline engine passenger cars and trucks: All California (CA), Massachusetts (MA), and New York (NY) Federal passenger cars, California, MA, and NY Medium Duty Passenger Vehicles (MDPVs) and trucks up to 14,000 lb Gross Vehicle Weight Rating (GVWR). Federal trucks from 8,500 lb to 14,000 lb GVWR will begin phasing in OBD-II starting in the 2004 model year. Federal heavy-duty trucks up to 10,000 lb GVWR choosing to certify using light duty truck provisions must comply with OBD-II requirements. Federal heavy-duty trucks over 8,500 lb GVWR that do not comply with OBD-II regulations must comply with OBD-I in order to meet the minimum Ford requirements. Passenger cars and trucks sold in Canada and Mexico have Federal calibrations, unless unique calibrations are certified for Mexico at high altitude.
2. Diesel Engine passenger cars and trucks: All passenger cars and California trucks up to 14,000 lb GVWR. Federal trucks from 8,500 lb to 14,000 lb GVWR began phase in of OBD-II starting in the 2004 model year.

Green States are states that choose to adopt California emission regulations. Green States receive California vehicles for all passenger cars and trucks less than 6,000 lbs. GVWR. Green States are MA, NY, Vermont (VT) and Maine (ME).

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 100,000, 120,000, or 150,000 (passenger cars), or 120,000 (trucks) mile emission standards. Partial Zero Emission Vehicle (PZEV), Super Ultra Low Emission Vehicle (SULEV-II), and Federal Tier 2 (Bin 3 and 4) vehicles can use the 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 will be illuminated within 2 driving 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. For the 2005 model year, pending DTCs will be displayed as long as the fault is present. Note that OBD II regulations required a complete fault-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 fault-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 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 DTC(s) have been 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.

Vehicles not required to comply with OBD-II requirements will use an OBD-I system. OBD-I systems are used on all Federal truck calibrations over 8,500 lb GVWR. OBD-I vehicles use the same data communication link, data link connector (DLC), and PCM software as the corresponding OBD-II vehicle. Differences between OBD-I and OBD-II vehicles may be removal of the rear oxygen sensor(s), fuel tank pressure sensor, canister vent solenoid, and PCM calibration. The table below lists what monitors and functions have been altered for the OBD-I calibration.

MONITOR/FEATURE - CALIBRATION

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 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 Comprehensive Component Monitor (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 ON-BOARD DIAGNOSTIC MONITORS and throughout this article.

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Catalyst Efficiency Monitor

The Catalyst Efficiency Monitor uses an oxygen sensor before and after the catalyst to infer the hydrocarbon (HC) efficiency based on the oxygen storage capacity of the catalyst. Under normal closed-loop fuel conditions, high efficiency catalysts have significant oxygen storage. This makes the switching frequency of the rear heated oxygen sensor (HO2S) very slow and reduces the amplitude of those switches as compared to the switching frequency and amplitude of the front HO2S. As the catalyst efficiency deteriorates due to thermal and/or chemical deterioration, its ability to store oxygen declines. The post-catalyst or downstream HO2S signal begins to switch more rapidly with increasing amplitude, approaching the switching frequency and amplitude of the pre-catalyst or upstream HO2S.

Note. The predominant failure mode for high mileage catalysts is chemical deterioration (phosphorus deposits on the front brick of the catalyst), not thermal deterioration.

All vehicles use a Federal Test Procedure based catalyst monitor. This simply means that the catalyst monitor must run during a standard Federal Test Procedure emission test. This differs from the 20-second steady state catalyst monitor used in 1994 through some 1996 vehicles. Currently, the 2 slightly different versions of the catalyst monitor that are used are the Switch Ratio method and the Index Ratio method. Beginning with the 2001 model year and beyond, both versions will continue to be used in subsequent model years.

Switch Ratio Method

1. In order to assess catalyst oxygen storage, the monitor counts front and rear HO2S switches during the part-throttle, closed-loop fuel condition after the engine is warmed-up and the inferred catalyst temperature is within limits. Front switches are accumulated in up to 9 different air mass regions or cells, although 3 air mass regions is typical. Rear switches are counted in a single cell for all air mass regions. When the required number of front switches has accumulated in each cell, the total number of rear switches is divided by the total number of front switches to compute a switch ratio. A switch ratio near 0.0 indicates high oxygen storage capacity, hence high HC efficiency. A switch ratio near 1.0 indicates low oxygen storage capacity, hence low HC efficiency. If the actual switch ratio exceeds a calibrated threshold switch ratio, the catalyst is considered failed. Inputs from the engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), mass air flow (MAF), crankshaft position (CKP), vehicle speed, and throttle position (TP) are required to enable the Catalyst Efficiency Monitor. Typical Switch Ratio Monitor Entry Conditions: Part throttle with no rapid throttle transients. 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 -6°C - 82°C (20°F - 180°F). Engine load is greater than 10%. Time since entering closed-loop is 30 seconds. Vehicle speed is between 8 and 112 km/h (5 and 70 mph). Inferred catalyst mid-bed temperature of 482°C (900°F). Mass air flow is between 1 and 5 lbs/min. Fuel level greater than 15%. EGR is between 1 and 12%.
2. The DTCs associated with this test are DTC P0420 (Bank 1 or Y-pipe system) and P0430 (Bank 2). Because an exponentially weighted moving average algorithm is used for malfunction determination, up to 6 driving cycles may be required to illuminate the MIL during normal customer driving. If the KAM is reset or the battery is disconnected, a malfunction illuminates the MIL in 2 drive cycles.

Index Ratio Method

1. In order to assess catalyst oxygen storage, the catalyst monitor counts front HO2S switches during part-throttle, closed-loop fuel conditions after the engine is warmed-up and the inferred catalyst temperature is within limits. Front switches are accumulated in up to 3 different air mass regions or cells. While catalyst monitoring entry conditions are being met, the front and rear HO2S signal lengths are continually being calculated. When the required number of front switches has accumulated in each cell, the total signal length of the rear HO2S is divided by the total signal length of the front HO2S to compute a catalyst index ratio. An index ratio near 0.0 indicates high oxygen storage capacity, hence high HC efficiency. A switch ratio near 1.0 indicates low oxygen storage capacity, hence low HC efficiency. If the actual index ratio exceeds the threshold index ratio, the catalyst is considered failed. Inputs from ECT or CHT, IAT, MAF, CKP, TP, and vehicle speed are required to enable the Catalyst Efficiency Monitor. 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 -6°C - 82°C (20°F - 180°F). Time since entering closed-loop is 30 seconds. Inferred rear HO2S sensor temperature of 482°C (900°F). EGR is between 1% and 12%. Part throttle, maximum rate of change is 0.2 volts/0.050 sec. Vehicle speed is between 8 and 112 km/h (5 and 70 mph). Fuel level is greater than 15%. First Air Flow Cell Engine RPM 1,000 to 1,300 RPM. Engine load 15 to 35%. Inferred catalyst temperature 454°C - 649°C (850°F - 1,200°F). Number of front HO2S switches is 50. Second Air Flow Cell Engine RPM 1,200 to 1,500 RPM. Engine load 20 to 35%. Inferred catalyst temperature 482°C - 677°C (900°F - 1,250°F). Number of front HO2S switches: 70. Third Air Flow Cell Engine RPM 1,300 to 1,600 RPM. Engine load 20 to 40%. Inferred catalyst temperature 510°C - 704°C (950°F - 1,300°F). Number of front HO2S switches is 30.
2. The DTCs associated with this test are DTC P0420 (Bank 1 or Y-pipe system) and P0430 (Bank 2). Because an exponentially weighted moving average algorithm is used for malfunction determination, up to 6 driving cycles may be required to illuminate the MIL during normal customer driving. If the KAM is reset or the battery is disconnected, a malfunction illuminates the MIL in 2 drive cycles.

General Catalyst Monitor Operation

Monitor execution is once per drive cycle. The typical monitor duration is 700 seconds. 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 sensors can be located in various configurations to monitor different kinds of exhaust systems. In-line 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 in-line 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 switch ratio. The rational for this strategy is that the catalyst nearest the engine will deteriorate first, allowing the catalyst monitor to be more sensitive, and illuminate the MIL properly at lower emission standards.

Note. 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 will 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 properly at lower emission standards.

Many applications that use partial-volume monitoring place the rear HO2S 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 sets of 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 HEATED OXYGEN SENSOR (HO2S) MONITOR .

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

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Comprehensive Component Monitor (CCM)

The CCM monitors for malfunctions in any powertrain electronic component or circuit that provides input or output signals to the PCM that can affect emissions and is not monitored by another OBD monitor. Inputs and outputs are, at a minimum, monitored for circuit continuity or proper range of values. Where feasible, inputs are also checked for rationality, and outputs are also checked for proper functionality.

The CCM covers many components and circuits and tests them in various ways depending on the hardware, function, and type of signal. For example, analog inputs such as throttle position or engine coolant temperature are typically checked for opens, shorts, and out-of-range values. This type of monitoring is carried out continuously. Some digital inputs like brake switch or crankshaft position rely on rationality checks - checking to see if the input value makes sense at the current engine operating conditions. These types of tests may require monitoring several components and can only be carried out under the appropriate test conditions.

Outputs such as coil drivers are checked for opens and shorts by monitoring a feedback circuit or smart driver associated with the output. Other outputs, such as relays, require additional feedback circuits to monitor the secondary side of the relay. Some outputs are also monitored for proper function by observing the reaction of the control system to a given change in the output command. An idle air control solenoid can be functionally tested by monitoring the idle RPM relative to the target idle RPM. Some tests can only be carried out under the appropriate test conditions. For example, the transmission shift solenoids can only be tested when the PCM commands a shift.

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

Scheme 9

1. Inputs: Air conditioning (A/C) pressure sensor, camshaft position (CMP) sensor, engine coolant temperature (ECT) sensor, fuel tank pressure (FTP) sensor, intake air temperature (IAT) sensor, mass air flow (MAF) sensor, throttle position (TP) sensor.
2. Outputs: EVAP canister purge valve, EVAP canister vent (CV) solenoid, fuel pump (FP), idle air control (IAC), intake manifold runner control (IMRC), shift solenoid (SS), torque converter clutch (TCC) solenoid, wide open throttle A/C cutout (WAC).
3. CCM is enabled after the engine starts and is running. A DTC is stored in KAM and the MIL is illuminated after 2 driving cycles when a malfunction is detected. Many of the CCM tests are also carried out during an on-demand self-test.

Evaporative Emission (EVAP) Leak Check Monitor

The EVAP leak check monitor is an on-board strategy designed to detect a leak from a hole (opening) equal to or greater than 0.508 mm (0.020 inch) in the enhanced EVAP system. The proper function of the individual components of the enhanced EVAP system, as well as its ability to flow fuel vapor to the engine, is also examined. The EVAP leak check monitor relies on the individual components of the enhanced EVAP system to either allow a natural vacuum to occur in the fuel tank or apply engine vacuum to the fuel tank and then seal the entire enhanced EVAP system from the atmosphere. The fuel tank pressure is then monitored to determine the total vacuum lost (bleed-up) for a calibrated period of time. Inputs from the engine coolant temperature (ECT) sensor or cylinder head temperature (CHT) sensor, intake air temperature (IAT) sensor, mass air flow (MAF) sensor, vehicle speed, fuel level input (FLI) and fuel tank pressure (FTP) sensor are required to enable the EVAP Leak Check Monitor.

Note. During the EVAP Leak Check Monitor Repair Verification Drive Cycle, clearing the continuous diagnostic trouble codes (DTCs) and resetting the emission monitors information in the powertrain control module (PCM) will bypass the minimum soak time required to complete the monitor. The EVAP Leak Check Monitor will not run if the key is turned off after clearing the continuous DTCs and resetting the emission monitors information in the PCM. The EVAP Leak Check Monitor will not run if a MAF sensor failure is indicated. The EVAP Leak Check Monitor will not initiate until the heated oxygen sensor (HO2S) monitor has completed.

Note. Some 2005 vehicle applications will add an engine off natural vacuum (EONV) check to the EVAP leak check monitor.

Engine On EVAP Leak Check Monitor

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

Scheme 10

1. The EVAP canister purge valve, also known as the vapor management valve (VMV), is used to control the flow of vacuum from the engine and create a target vacuum on the fuel tank.
2. The canister vent (CV) solenoid is used to seal the EVAP system from the atmosphere. It is closed by the PCM (100% duty cycle) which then allows the EVAP canister purge valve to obtain the target vacuum on the fuel tank.
3. The FTP sensor will be used by the engine on EVAP leak check monitor to determine if the target vacuum necessary to carry out the leak check on the fuel tank is reached. Some vehicle applications with the engine on EVAP leak check monitor use a remote in-line FTP sensor. Once the target vacuum on the fuel tank is achieved, the change in fuel tank vacuum over a calibrated period of time will determine if a leak exists.
4. If the initial target vacuum cannot be reached, DTC P0455 (gross leak detected) will be set. The engine on EVAP leak check monitor will abort and not continue with the leak check portion of the test. For some vehicle applications, if the initial target vacuum cannot be reached after a refueling event and the purge vapor flow is excessive, DTC P0457 (fuel cap off) is set. If the initial target vacuum cannot be reached and the purge flow is too small, DTC P1443 (no purge flow condition) is set. If the initial target vacuum is exceeded, a system flow fault exists and DTC P1450 (unable to bleed-up fuel tank vacuum) is set. The engine on EVAP leak check monitor will abort and not continue with the leak check portion of the test. If the target vacuum is obtained on the fuel tank, the change in the fuel tank vacuum (bleed-up) will be calculated for a calibrated period of time. The calculated change in fuel tank vacuum will be compared to a calibrated threshold for a leak from a hole (opening) of 1.016 mm (0.040 inch) in the enhanced EVAP system. If the calculated bleed-up is less than the calibrated threshold, the enhanced EVAP system passes. If the calibrated bleed-up exceeds the calibrated threshold, the test will abort and rerun the test up to 3 times. If the bleed-up threshold is still being exceeded after 3 tests, a vapor generation test must be carried out before DTC P0442 (small leak detected) will be set. This is accomplished by returning the enhanced EVAP system to atmospheric pressure by closing the EVAP canister purge valve and opening the CV solenoid. Once the FTP sensor observes the fuel tank is at atmospheric pressure, the CV solenoid closes and seals the enhanced EVAP system. The fuel tank pressure build-up, over a calibrated period of time will be compared to a calibrated threshold for pressure build-up due to vapor generation. If the fuel tank pressure build-up exceeds the threshold, the leak test results are invalid due to vapor generation. The engine on EVAP leak check monitor will attempt to retest again. If the fuel tank pressure build-up does not exceed the threshold, the leak test results are valid and DTC P0442 will be set.
5. If the 1.016 mm (0.40 inch) test passes, the test time is extended to allow the 0.508 mm (0.020 inch) test to run. The calculated change in fuel vacuum over the extended time is compared to a calibrated threshold for a leak from a 0.508 mm (0.020 inch) hole (opening). If the calculated bleed-up exceeds the calibrated threshold, the vapor generation test is run. If the vapor generation test passes (no vapor generation), an internal flag is set in the PCM to run a 0.508 mm (0.020 inch) test at idle (vehicle stopped). On the next start following a long engine off period, the enhanced EVAP system will be sealed and evacuated for the first 10 minutes of operation. If the appropriate conditions are met, a 0.508 mm (0.020 inch) leak check is conducted at idle. If the test at idle fails, a DTC P0456 will be set. There is no vapor generation test with the idle test. NOTE: If the vapor generation is high on some vehicle enhanced EVAP systems, where the monitor does not pass, the result is treated as a no test. Thereby, the test is complete for the day.
6. The MIL is activated for DTCs P0442, P0455, P0456, P0457, P1443, and P1450 (or P0446) after 2 occurrences of the same fault. The MIL can also be activated for any enhanced EVAP system component DTCs in the same manner. The enhanced EVAP system component DTCs P0443, P0452, P0453, and P1451 are tested as part of the CCM.

Engine Off Natural Vacuum (EONV) EVAP Leak Check Monitor

The EONV EVAP leak check monitor is executed during key off, after the engine on EVAP leak check monitor is completed. The EONV EVAP leak check monitor determines a leak is present when the naturally occurring change in fuel tank pressure or vacuum does not exceed a calibrated limit during a calibrated amount of time. A separate, low power consuming, microprocessor in the PCM will manage the EONV leak check. The engine off EVAP leak check monitor is executed by the individual components of the enhanced EVAP system as follows

Scheme 11

1. The EVAP canister purge valve, also known as the vapor management valve (VMV), is normally closed at key off.
2. The normally open canister vent (CV) remains open for a calibrated amount of time to allow the fuel tank pressure to stabilize with the atmosphere. During this time period the FTP sensor is monitored for an increase in pressure. If pressure remains below a calibrated limit the CV is closed by the PCM (100% duty cycle) and seals the EVAP system from the atmosphere.
3. The FTP sensor is used by the EONV EVAP leak check monitor to determine if the target pressure or vacuum necessary to complete the EONV EVAP leak check monitor on the fuel tank is reached. Some vehicle applications with the EONV EVAP leak check monitor use a remote in-line FTP sensor. If the target pressure or vacuum on the fuel tank is achieved within the calibrated amount of time the test is complete.
4. The EONV EVAP leak check monitor uses the naturally occurring change in fuel tank pressure as a means to detect a leak in the EVAP system. At key off, a target pressure and vacuum is determined by the PCM. These target values are based on the fuel level and the ambient temperature at key off. As the fuel tank temperature increases, the pressure in the tank will increase and as the temperature decreases a vacuum will develop. If a leak is present in the EVAP system the fuel tank pressure or vacuum will not exceed the target value during the testing time period. The EONV EVAP leak check monitor begins at key off. After key off the normally open canister vent (CV) remains open for a calibrated amount of time to allow the fuel tank pressure to stabilize with the atmosphere. During this time period the FTP sensor is monitored for an increase in pressure. If pressure remains below a calibrated limit the CV is closed by the PCM (100% duty cycle) and seals the EVAP system from the atmosphere. If the pressure on the fuel tank decreases after the EVAP system is sealed, the EONV EVAP leak check monitor begins to monitor the fuel tank pressure. When the target vacuum is exceeded within the calibrated amount of time the test completes and the fuel tank pressure and time since key off information is stored. If the target vacuum is not reached in the calibrated amount of time, a leak is suspected and the fuel tank pressure and time since key off information is stored. If the pressure on the fuel tank increases after the EVAP system is sealed, but does not exceed the target pressure within a calibrated amount of time the CV is opened to allow the fuel tank pressure to again stabilize with the atmosphere. After a calibrated amount of time the CV is closed by the PCM and seals the EVAP system. When the fuel tank pressure exceeds either the target pressure or vacuum within the calibrated amount of time the test completes and the fuel tank pressure and time since key off information is stored. If the target pressure or vacuum is not reached in the calibrated amount of time, a leak is suspected and the fuel tank pressure and time since key off information is stored. When a leak is suspected, the PCM will use the stored fuel tank pressure and time since key off information from an average run of 4 tests to suspect a leak. If a leak is still suspected after 2 consecutive runs of 4 tests, (8 total tests) DTC P0456 is set and the MIL is illuminated.
5. The EONV EVAP leak check monitor is controlled by a separate low power consuming microprocessor inside the PCM. The fuel level indicator, fuel tank pressure, and battery voltage are inputs to the microprocessor. The microprocessor outputs are the CV solenoid and the stored test information. If the separate microprocessor is unable to control the CV solenoid or communicate with other processors DTC P260F is set.
6. The MIL is activated for DTCs P0456 and P260F. The MIL can also be activated for any enhanced EVAP system component DTCs in the same manner. The enhanced EVAP system component DTCs P0443, P0446, P0452, P0453, and P1451 are tested as part of the CCM.

Exhaust Gas Recirculation (EGR) System Monitor - Delta Pressure Feedback (DPFE) EGR and EGR System Module (ESM)

The EGR System Monitor is an on-board strategy designed to test the integrity and flow characteristics of the EGR system. The monitor is activated during EGR system operation and after certain base engine conditions are satisfied. Input from the engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), throttle position (TP), and crankshaft position (CKP) sensors is required to activate the monitor. Once activated, the EGR System Monitor will carry out each of the tests described below during the engine modes and conditions indicated. Some of the EGR System Monitor tests are also carried out during an on-demand self-test.

Note. The DPFE sensor, EGR vacuum regulator (EVR) solenoid, manifold absolute pressure (MAP) sensor and the EGR valve itself are integrated into one unit in the ESM EGR assembly. The ESM is not repairable. If any one component fails within the ESM, the entire ESM assembly must be replaced.

Scheme 12

Scheme 13

1. The DPFE sensor and circuit are continuously tested for opens and shorts. The monitor looks for the DPFE circuit voltage to exceed the maximum or minimum allowable limits. The DTCs associated with this test are DTCs P0405 or P1400 and P0406 or P1401.
2. The EVR solenoid is continuously tested for opens and shorts. The monitor looks for an EVR circuit voltage that is inconsistent with the EVR circuit commanded output state. The DTC associated with this test is DTC P0403 or P1409.
3. The test for a stuck open EGR valve or EGR flow at idle is continuously carried out at idle (TP sensor indicating closed throttle). The monitor compares the DPFE circuit voltage at idle to the DPFE circuit voltage stored during key on engine off (KOEO) to determine if EGR flow is present at idle. The DTC associated with this test is DTC P0402.
4. The DPFE sensor hoses are tested once per drive cycle for disconnect and plugging. The test is carried out with the EGR valve closed and during a period of acceleration. The PCM will momentarily command the EGR valve closed. The monitor looks for the DPFE sensor voltage to be inconsistent for a no flow voltage. A voltage increase or decrease during acceleration while the EGR valve is closed may indicate a fault with a signal hose during this test. The DTCs associated with this test are DTC P1405 and P1406.
5. The EGR flow rate test is carried out during a steady state when the engine speed and load are moderate and the EVR duty cycle is high. The monitor compares the actual DPFE circuit voltage to a desired EGR flow voltage for that state to determine if the EGR flow rate is acceptable or insufficient. This is a system test and may trigger a DTC for any fault causing the EGR system to fail. The DTC associated with this test is DTC P0401. DTC P1408 is similar to P0401 but is carried out during key on engine running (KOER) self-test conditions.
6. The MIL is activated after one of the above tests fails on 2 consecutive drive cycles.

Electric Exhaust Gas Recirculation (EEGR) System Monitor

The EEGR System Monitor is an on-board strategy designed to test the integrity and flow characteristics of the EGR system. The monitor is activated during EGR system operation and after certain base engine conditions are satisfied. Input from the engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), throttle position (TP), crankshaft position (CKP), mass air flow (MAF), and manifold absolute pressure (MAP) sensors is required to activate the EGR System Monitor. Once activated, the EGR System Monitor will carry out each of the tests described below during the engine modes and conditions indicated. Some of the EGR System Monitor tests are also carried out during an on-demand self-test.

The EEGR monitor consists of an electrical and functional test that checks the stepper motor and the EEGR system for proper flow. The PCM controls the EEGR valve by commanding from 0 to 52 discreet increments or steps to get the valve from fully closed to fully open. The stepper motor electrical test is a continuous check of the 4 electric stepper motor coils and circuits to the PCM. A malfunction is indicated if an open circuit, short to power, or short to ground has occurred in one or more of the stepper motor coils or circuits for a calibrated period of time. If a malfunction has been detected, the EEGR system will be disabled, setting DTC P0403. Additional monitoring will be suspended for the remainder of the drive cycle, or until the next engine startup.

After the vehicle has warmed up and normal EEGR flow rates are being commanded by the PCM, the EEGR flow check is carried out. The flow test is carried out once per drive cycle when a minimum amount of exhaust gas is requested and the remaining entry conditions required to initiate the test are satisfied. If a malfunction is detected, the EEGR system, as well as the EEGR monitor, is disabled until the next engine startup.

The EEGR flow test is done by observing the behavior of 2 different values: MAP - the analog MAP sensor reading, and inferred MAP - calculated from the MAF sensor, throttle position, RPM, etc. During normal, steady-state operating conditions, EEGR is intrusively commanded ON to a specified percentage. Then, EEGR is commanded OFF. If the EEGR system is working properly there is a significant difference in both the observed and the calculated values of MAP between the EGR-ON and the EGR-OFF states.

When the flow test entry conditions have been satisfied, EEGR is commanded to flow at a calibrated test rate (about 10%). At this time, the value of MAP is recorded (EGR-ON MAP). The value of inferred MAP EGR-ON IMAP is also recorded. Next the EEGR is commanded off (0%). Again, the value of MAP is recorded (EGR-OFF MAP). The value of EGR-OFF IMAP is also recorded. Typically, 7 such ON/OFF samples are taken. After all the samples have been taken, the average EGR-ON MAP, EGR-ON IMAP, EGR-OFF MAP and EGR-OFF IMAP values are stored.

Then the difference between the EGR-ON and EGR-OFF value is calculated

1. MAP-delta = EGR-ON MAP - EGR-OFF MAP (analog MAP)
2. IMAP-delta = EGR-ON IMAP - EGR-OFF IMAP (inferred MAP)

If the sum of MAP-delta and IMAP-delta exceeds a maximum threshold or falls to less than a minimum threshold, DTC P0400 (high or low flow malfunction) is registered.

As an additional check, if the EGR-ON MAP exceeds a maximum threshold (BARO, a calibrated value), DTC P0400 (low flow) is set. This check is carried out to detect reduced EGR flow on systems where the MAP pickup point is not located in the intake manifold, but is located just upstream of the EEGR valve in the EEGR delivery tube.

Note. BARO is inferred at engine startup using the KOEO MAP sensor reading. It is updated during high, part-throttle or high RPM engine operation.

If the inferred ambient temperature is less than -7°C (20°F), greater than 54°C (130°F), or the altitude is greater than 8,000 feet (BARO less than 22.5 in-Hg), the EEGR flow test cannot be reliably done. In these conditions, the EEGR flow test is suspended and a timer starts to accumulate the time in these conditions. When the vehicle leaves these extreme conditions, the timer starts to decrement, and if conditions permit, will attempt to complete the EGR flow monitor. If the timer reaches 800 seconds, the EEGR flow test is disabled for the remainder of the current driving cycle and the EGR Monitor will be set to a ready condition.

A DTC P1408, like the P0400, will indicate a EGR flow failure (outside the minimum or maximum limits) but is only set during the KOER self-test. The P0400 and P0403 are MIL codes. P1408 is a non-MIL code.

Scheme 14

Fuel System Monitor

The fuel system monitor is an on-board strategy designed to monitor the fuel control system. The fuel control system uses fuel trim tables stored in the PCMs KAM to compensate for the variability that occurs in fuel system components due to normal wear and aging. Fuel trim tables are based on engine RPM and engine load. During closed-loop fuel control, the fuel trim strategy learns the corrections needed to correct a biased rich or lean fuel system. The correction is stored in the fuel trim tables. The fuel trim has 2 means of adapting: Long Term Fuel Trim and a Short Term Fuel Trim. Both are described in greater detail under powertrain Control Software, FUEL TRIM . Long Term relies on the fuel trim tables and Short Term refers to the desired air/fuel ratio parameter called LAMBSE. LAMBSE is calculated by the PCM from HO2S inputs and helps maintain a 14.7:1 air/fuel ratio during closed-loop operation. Short Term Fuel Trim and Long Term Fuel Trim work together. If the HO2S indicates the engine is running rich, the PCM will correct the rich condition by moving the Short Term Fuel Trim into the negative range (less fuel to correct for a rich combustion). If after a certain amount of time the Short Term Fuel Trim is still compensating for a rich condition, the PCM learns this and moves the Long Term Fuel Trim into the negative range to compensate and allow the Short Term Fuel Trim to return to a value near 0%. Inputs from the engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), mass air flow (MAF) sensors are required to activate the fuel trim system, which in turn activates the fuel system monitor. Once activated, the fuel system monitor looks for the fuel trim tables to reach the adaptive clip (adaptive limit) and LAMBSE to exceed a calibrated limit. The fuel system monitor will store the appropriate DTC when a fault is detected as described below.

Scheme 15

1. The heated oxygen sensor (HO2S) detects the presence of oxygen in the exhaust and provides the PCM with feedback indicating air/fuel ratio.
2. A correction factor is added to the fuel injector pulse width calculation and the mass air flow calculation, according to the Long and Short Term Fuel Trims as needed to compensate for variations in the fuel system.
3. When deviation in the LAMBSE parameter increases, air/fuel control suffers and emissions increase. When LAMBSE exceeds a calibrated limit and the fuel trim table has clipped, the Fuel System Monitor sets a DTC as follows: The DTCs associated with the monitor detecting a lean shift in fuel system operation are DTCs P0171 (Bank 1) and P0174 (Bank 2). The DTCs associated with the monitor detecting a rich shift in fuel system operation are DTCs P0172 (Bank 1) and P0175 (Bank 2).
4. The MIL is activated after a fault is detected on 2 consecutive drive cycles. Typical Fuel System Monitor Entry Conditions: RPM range greater than idle. Air mass range greater than 5.67 g/sec (0.75 lb/min). Purge duty cycle of 0%. Typical Fuel Monitor Malfunction Thresholds: Lean Malfunction: LONGFT greater than 25%, SHRTFT greater than 5%. Rich Malfunction: LONGFT less than 25%, SHRTFT less than 10%

Heated Oxygen Sensor (HO2S) Monitor

The HO2S monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration which can affect emissions. The fuel control or stream 1 HO2S sensors are checked for proper output voltage and response rate (the time it takes to switch from lean to rich or rich to lean). Stream 2 HO2S sensors are used for catalyst monitoring, and stream 3 HO2S sensors used for fore-aft oxygen sensor (FAOS) control are also monitored for proper output voltage. Input is required from the engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), mass air flow (MAF) sensors, and crankshaft position (CKP) sensors to activate the HO2S monitor. The fuel system monitor and misfire detection monitor must also have completed successfully before the HO2S monitor is enabled.

Scheme 16

Scheme 17

1. The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1), the HO2S will generate a voltage between zero and 0.45 volt. Rich of stoichiometric, the HO2S will generate a voltage between 0.45 and 1.0 volt. The HO2S monitor evaluates the stream 1 (fuel control), stream 2 (catalyst monitor), and stream 3 (FAOS control) HO2S for proper function.
2. The time between HO2S switches is monitored after vehicle startup and during closed loop fuel conditions. Excessive time between switches or no switches since startup indicates a malfunction. Since lack of switching malfunctions can be caused by HO2S sensor malfunctions or by shifts in the fuel system, DTCs are stored that provide additional information for the lack of switching malfunction. Different DTCs indicate whether the sensor always indicates lean/disconnected (P1131 or P2195, P1151 or P2197), or always indicates rich (P1132 or P2196, P1152, or P2198). 2005 MY vehicles will monitor the HO2S signal for high voltage, in excess of 1.1 volts and store a unique DTC. (P0132, P0152). An over-voltage condition is caused by a HO2S heater or battery power short to the HO2S signal line. A functional test of the rear HO2S sensors is done during normal vehicle operation. The peak rich and lean voltages are continuously monitored. Voltages that exceed the calibrated rich and lean thresholds indicate a functional sensor. If the voltages have not exceeded the thresholds after a long period of vehicle operation, the air/fuel ratio may be forced rich or lean in an attempt to get the rear sensor to switch. This situation normally occurs only with a green catalyst (less than 500 miles). If the sensor does not exceed the rich and lean peak thresholds, a malfunction is indicated. 2005 MY vehicles will monitor the rear HO2S signal for high voltage, in excess of 1.1 volts and store a unique DTC. (P0138, P0158). An over-voltage condition is caused by a HO2S heater or battery power short to the HO2S signal line.
3. The MIL is activated after a fault is detected on 2 consecutive drive cycles.
4. Some 2005 Partial Zero Emission Vehicles (PZEV) will use 3 sets of HO2S sensors. The front sensors (HO2S11/HO2S21) are the primary fuel control sensors. The next sensors downstream in the exhaust are used to monitor the light-off catalyst (HO2S12/HO2S22). The last sensors downstream in the exhaust (HO2S13/HO2S23) are used for very long term fuel trim in order to optimize catalyst efficiency (FAOS Control). The current PZEV vehicle uses a 4-cylinder engine, so only the Bank 1 DTCs are used. The HO2S Monitor DTCs can be categorized as follows: HO2S signal circuit malfunction - P0131, P0136, P0151, P0156. HO2S slow response rate - P0133, P0153. HO2S circuit high voltage - P0132, P0138, P0144, P0152, P0158, P0164. HO2S heater circuit malfunction - P0135, P0141, P0155, P0161, P0147, P0167. HO2S heater current malfunction - P0053, P0054, P0055, P0059, P0060, P0061. Downstream HO2S not running in on-demand self-test - P1127. Swapped HO2S connectors - P0040, P0041, P1128, P1129, P2278. HO2S lack of switching - P1131, P1132, P1151, P1152, P2195, P2196, P2197, P2198. HO2S lack of switching (sensor indicates lean) - P1137, P1157, P2270, P2272, P2274, P2276. HO2S lack of switching (sensor indicates rich) - P1138, P1158, P2271, P2273, P2275, P2277.

Misfire Detection Monitor

The Misfire Detection Monitor is an on-board strategy designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause. The Misfire Detection Monitor will be enabled only when certain base engine conditions are first satisfied. Input from the engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), mass air flow (MAF) sensors is required to enable the monitor. The Misfire Detection Monitor is also carried out during an on-demand self-test.

Scheme 18

1. The PCM synchronized ignition spark is based on information received from the CKP sensor. The CKP signal generated is also the main input used in determining cylinder misfire.
2. The input signal generated by the CKP sensor is derived by sensing the passage of teeth from the crankshaft position wheel mounted on the end of the crankshaft.
3. The input signal to the PCM is then used to calculate the time between CKP edges and the crankshaft rotational velocity and acceleration. By comparing the accelerations of each cylinder event, the power loss of each cylinder is determined. When the power loss of a particular cylinder is sufficiently less than a calibrated value and other criteria are met, then the suspect cylinder is determined to have misfired.

Misfire Monitor Operation

There are 2 different misfire monitoring technologies used in the 2005 MY. They are low data rate (LDR) and high data rate (HDR). The LDR system is capable of meeting the Federal Test Procedure monitoring requirements on most engines and is capable of meeting the full-range of misfire monitoring requirements on 4-cylinder engines. The HDR system is capable of meeting the full-range of misfire monitoring requirements on 6 and 8 cylinder engines. HDR is being phased in on these engines to meet the full-range of misfire phase-in requirements specified in the OBD regulations. All engines except the 6.8L V-10 are full-range capable. All 2005 MY software allows for detection of any misfires that occur 6 engine revolutions after initially cranking the engine. This meets the new OBD requirement to identify misfires within 2 engine revolutions after exceeding the warm drive, idle RPM.

Low Data Rate System (LDR)

The LDR misfire monitor uses a low-data-rate crankshaft position signal, one position reference signal at 10 degrees BTDC for each cylinder event. The PCM calculates the crankshaft rotational velocity for each cylinder from this crankshaft position signal. The acceleration for each cylinder can then be calculated using successive velocity values. The changes in overall engine RPM are removed by subtracting the median engine acceleration over a complete engine cycle. The resulting deviant cylinder acceleration values are used in evaluating misfire in the GENERIC MISFIRE PROCESSING .

High Data Rate System (HDR)

The HDR misfire monitor uses a high data rate crankshaft position signal, 18 position references per crankshaft revolution (20 on a V-10). This high-resolution signal is processed using 2 different algorithms. The first algorithm, called pattern cancellation, is optimized to detect low rates of misfire. The algorithm learns the normal pattern of cylinder accelerations from the mostly good firing events and is then able to accurately detect deviations from that pattern. The second algorithm is optimized to detect hard misfires, one or more continuously misfiring cylinders. This algorithm filters the high-resolution crankshaft velocity signal to remove some of the crankshaft torsional vibrations that degrade signal to noise. This significantly improves detection capability for continuous misfires. Both algorithms produce a deviant cylinder acceleration value, which is used in evaluating misfire in the General Misfire Algorithm Processing below. Due to the high data processing requirements, the HDR algorithms could not be implemented in the PCM microprocessor. They are implemented in a separate chip in the PCM called an AICE chip. The PCM microprocessor communicates with the AICE chip using a dedicated serial communication link. The output of the AICE chip (the cylinder acceleration values) is sent to the PCM microprocessor for additional processing as described below. Lack of serial communication between the AICE chip and the PCM microprocessor, or an inability to synchronize the crankshaft or camshaft sensors inputs sets a P1309 DTC. For 2005 MY software, the P1309 DTC is being split into 2 separate DTCs. A P0606 will be set if there is a lack of serial communication between the AICE chip and the PCM microprocessor. A P1336 will be set if there is an inability to synchronize the crank or cam sensors inputs. This change was made to improve repairability. A P0606 generally results in PCM replacement while a P1336 points to a cam sensor that is out of synchronization with the crank. Profile correction software is used to learn and correct for mechanical inaccuracies in crankshaft tooth spacing under de-fueled engine conditions (requires 3 decelerations from 97 to 64 km/h (60 to 40 mph) with no-braking after the keep alive memory (KAM) has been reset). If the KAM has been reset, the PCM microprocessor initiates a special routine which computes correction factors for each of the 18 (or 20) position references and sends these correction factors back to the AICE chip to be used for subsequent misfire signal processing. These learned corrections improve the high RPM capability of the monitor. The misfire monitor is not active until a profile has been learned.

Generic Misfire Processing

The acceleration that a piston undergoes during a normal firing event is directly related to the amount of torque that cylinder produces. The calculated piston/cylinder acceleration value(s) are compared to a misfire threshold that is continuously adjusted based on inferred engine torque. Deviant accelerations exceeding the threshold are conditionally labeled as misfires. The calculated deviant acceleration value(s) are also evaluated for noise. Normally, misfire results in a nonsymmetrical loss of cylinder acceleration. Mechanical noise, such as rough roads or high RPM/light load conditions, will produce symmetrical acceleration variations. Cylinder events that indicate excessive deviant accelerations of this type are considered noise. Noise-free deviant acceleration exceeding a given threshold is labeled a misfire. The number of misfires are counted over a continuous 200 revolution and 1000 revolution period. The revolution counters are not reset if the misfire monitor is temporarily disabled such as for negative torque mode. At the end of the evaluation period, the total misfire rate and the misfire rate for each individual cylinder is computed. The misfire rate is evaluated every 200 revolution period (Type A) and compared to a threshold value obtained from an engine speed/load table. This misfire threshold is designed to prevent damage to the catalyst due to sustained excessive temperature 871°C (1600°F) for Pt/Pd/Rh conventional washcoat, 899°C (1650°F) for Pt/Pd/Rh advanced washcoat and 982°C (1800°F) for Pd-only high tech washcoat. If the misfire threshold is exceeded and the catalyst temperature model calculates a catalyst mid-bed temperature that exceeds the catalyst damage threshold, the MIL blinks at a 1 Hz rate while the misfire is present. If the threshold is again exceeded on a subsequent driving cycle, the MIL is illuminated. If a single cylinder is indicated to be consistently misfiring in excess of the catalyst damage criteria, the fuel injector to that cylinder may be shut off for a period of time to prevent catalyst damage. Up to 2 cylinders may be disabled at the same time. This fuel shut-off feature is used on many 8-cylinder engines and some 6-cylinder engines. It is never used on a 4-cylinder engine. Next, the misfire rate is evaluated every 1000 revolution period and compared to a single (Type B) threshold value to indicate an emission-threshold malfunction, which can be either a single 1000 over-rev event from startup or 4 subsequent 1000 over-rev events on a drive cycle after start-up. Many 2005 MY vehicles will set a P0316 DTC if the Type B malfunction threshold is exceeded during the first 1,000 revolutions after engine startup. This DTC is stored in addition to the normal P03xx DTC that indicates the misfiring cylinder(s).

Profile Correction

Profile correction software is used to learn and correct for mechanical inaccuracies in the crankshaft position wheel tooth spacing. Since the sum of all the angles between the crankshaft teeth must equal 360°, a correction factor can be calculated for each misfire sample interval that makes all the angles between individual teeth equal. To prevent any fueling or combustion differences from affecting the correction factors, learning is done during deceleration-fuel cutout. The correction factors are learned during closed-throttle, non-braking, de-fueled decelerations in the 97 to 64 km/h (60 to 40 mph) range after exceeding 97 km/h (60 mph) (likely to correspond to a freeway exit condition). In order to minimize the learning time for the correction factors, a more aggressive deceleration-fuel cutout strategy may be employed when the conditions for learning are present. The corrections are typically learned in a single deceleration, but can be learned during up to 3 such decelerations. The mature correction factors are the average of a selected number of samples. A low data rate misfire system will typically learn 4 such corrections in this interval, while a high data rate system will learn 36 or 40 in the same interval (data is actually processed in the AICE chip). In order to assure the accuracy of these corrections, a tolerance is placed on the incoming values such that an individual correction factor must be repeatable within the tolerance during learning. This is to reduce the possibility of learning corrections on rough road conditions which could limit misfire detection capability. Since inaccuracies in the wheel tooth spacing can produce a false indication of misfire, the misfire monitor is not active until the corrections are learned. In the event of battery disconnection or loss of Keep Alive Memory, the correction factors are lost and must be relearned. If the software is unable to learn a profile after 3, 97 to 64 km/h (60 to 40 mph) deceleration cycles, a P0315 DTC is set.

Misfire Monitor Specifications

Misfire Monitor Operation: DTCs P0300 to P0310 (general and specific cylinder misfire), P1309 (no cam/crank synchronization, AICE chip malfunction), P1336 (no cam/crank synchronization), P0606 (AICE chip malfunction), P0315 (unable to learn profile), P0316 (misfire during first 1,000 revolutions after start-up). The monitor execution is continuous, misfire rate calculated every 200 or 1000 revolutions. The monitor does not have a specific sequence. The CKP and CMP sensors have to be OK to run the monitor. The monitoring duration is the entire driving cycle (see disablement conditions below)

Typical misfire monitor entry conditions: Entry condition minimum/maximum time since engine start-up is 0 seconds, engine coolant temperature is -7°C to 121°C (20°F to 250°F), RPM range is (full-range misfire certified, with 2 revolution delay) 2 revolutions after exceeding 150 RPM below drive idle RPM to red-line on tach or fuel cutoff, profile correction factors learned in KAM are Yes, and the fuel tank level is 15%.

Typical misfire temporary disablement conditions: Temporary disablement conditions: Closed throttle deceleration (negative torque, engine being driven), Fuel shut-off due to vehicle-speed limiting or engine-RPM limiting mode, and a high rate of change of torque (heavy throttle tip-in or tip out)

The Profile Learning operation includes DTCs P0315 - unable to learn profile in 3 97 to 64 km/h (60 to 40 mph) decelerations and P1309 - AICE chip communication failure; Monitor Execution is once per KAM reset; The Monitor Sequence: Profile must be learned before the misfire monitor is active; The CKP and CMP sensors are required to be OK; AICE communication errors, CKP/CMP in synch. The Monitoring Duration is 10 cumulative seconds in conditions (a maximum of 3, 97 to 64 km/h (60 to 40 mph) de-fueled decelerations).

Typical profile learning entry conditions: Entry conditions from minimum to maximum: Engine in deceleration-fuel cutout mode for 4 engine cycles the brakes are not applied, the engine RPM is 1,300 to 3,700 RPM, the change is less than 600 RPM, the vehicle speed is 48 to 112 km/h (30 to 75 mph), and the learning tolerance is 1%.

Positive Crankcase Ventilation (PCV) System Monitor

The PCV monitor consists of a modified PCV system design. The PCV valve is installed into the rocker cover using a quarter-turn cam-lock design to prevent accidental disconnection. High retention force molded plastic lines are used from the PCV valve to the intake manifold. The diameter of the lines and the intake manifold entry fitting are increased so that inadvertent disconnection of the lines after a vehicle is repaired will cause either an immediate engine stall or will not allow the engine to be restarted. In the event that the vehicle does not stall if the line between the intake manifold and PCV valve is inadvertently disconnected, the vehicle will have a large vacuum leak that will cause the vehicle to run lean at idle. This will illuminate the MIL after 2 consecutive driving cycles and will store one or more of the following DTCs: Lack of HO2S sensor switches, bank 1 (P1131 or P2195), Lack of HO2S sensor switches bank 2 (P1151 or P2197), fuel system lean, bank 1 (P0171) or fuel system lean, bank 2 (P0174).

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

Secondary Air Injection (AIR) System Monitor - Electric Secondary Air Injection Pump System

The Secondary Air Injection (AIR) System Monitor is an on-board strategy designed to monitor the proper function of the secondary air injection system. The AIR monitor for the electric secondary air injection pump system consists of 2 monitor circuits: an AIR circuit to diagnose concerns with the primary circuit side of the AIR relay, and an AIR monitor circuit to diagnose concerns with the secondary circuit side of the AIR relay. A functional check is also carried out that tests the ability of the AIR system to inject air into the exhaust. The functional check relies upon HO2S sensor feedback to determine the presence of air flow. The monitor is enabled during AIR system operation and only after certain base engine conditions are first satisfied. Input is required from the engine coolant temperature (ECT) or cylinder head temperature (CHT), intake air temperature (IAT), crankshaft position (CKP) sensors and the HO2S monitor test must also have passed without a fault detection to enable the AIR monitor. The AIR monitor is also activated during on-demand self-test.

Scheme 19

1. On the primary side of the AIR relay, open and short circuit faults are detected during normal operation by the PCM output driver. This circuit energizes the relay and the vacuum-operated check and solenoid control valves. The DTC associated with this test is DTC P0412.
2. On the secondary side of the AIR relay, the AIR monitor circuit is held low by the resistance path through the AIR pump when the pump is off. If the AIR monitor circuit is high there is either an open circuit to the PCM from the pump or there is power supplied to the AIR pump. If the AIR monitor is low when the pump is commanded on, there is either an open circuit from the AIR relay or the AIR relay has failed to supply power to the pump. The DTCs associated with this test are DTCs P2257 and P2258.
3. The functional check may be done in 2 parts: at startup when the AIR pump is normally commanded on, or during a hot idle if the startup test was not able to be carried out. The flow test relies upon the HO2S to detect the presence of additional air in the exhaust when introduced by the secondary air injection system. The DTC associated with this test is DTC P0411.
4. The MIL is activated after one of the above tests fail on 2 consecutive drive cycles.

Thermostat Monitor

The thermostat monitor is designed to verify proper thermostat operation. This monitor will be executed once per drive cycle and has a monitor run duration of 300-800 seconds. If a malfunction occurs, a diagnostic trouble code P0125 or P0128 is set and the malfunction indicator lamp will be illuminated.

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

The target temperature will be calibrated to the thermostat regulating temperature minus 11°C (20°F). For a typical 90°C (195°F) thermostat, the warm-up temperature would be calibrated to 79°C (175°F). For the 2005 model year, some vehicle calibrations may lower the target temperature below 27°C (50°F) for vehicles that do not warm-up to thermostat regulating temperatures in the 11°C (20°F) to 27°C (50°F) ambient temperature range.

Scheme 20

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

Variable Cam Timing (VCT) Monitor

The VCT output driver in the powertrain control module (PCM) is checked electrically for opens and shorts. The VCT system is checked functionally by monitoring the closed loop cam position error correction. If the proper cam position can not be maintained and the system has an advance or retard error greater than the malfunction threshold, a VCT control malfunction is indicated.

For additional VCT information, refer to VARIABLE CAM TIMING (VCT) SYSTEM .

Malfunction Indicator Lamp (MIL)

The MIL notifies the driver that the powertrain control module (PCM) has detected an OBD emission-related component or system fault. When this occurs, an OBD diagnostic trouble code (DTC) will be set.

Scheme 21

Scheme 22

1. The MIL is located in the instrument cluster and is labeled CHECK ENGINE, SERVICE ENGINE SOON or the ISO standard engine symbol.
2. The MIL is illuminated during the instrument cluster prove out for approximately 4 seconds.
3. For applications with a dedicated hard wire MIL circuit, the PCM will illuminate the MIL until a profile ignition pickup (PIP) signal is detected. For 2005, the following vehicles use a hard wire circuit: Crown Victoria/Grand Marquis, Explorer Sport Trac, and Ranger.
4. The MIL will remain illuminated after instrument cluster prove out if: an emission related concern and DTC exists. no PIP signal is detected (applications with a dedicated hard-wire MIL circuit). The PIP signal is generated in the PCM using the crankshaft position (CKP) sensor. For these applications, the MIL can be helpful in diagnosing a no start. the PCM does not send a control message to the instrument cluster (applications with the MIL controlled through the communication link). the PCM is operating in the Hardware Limited Operation Strategy (HLOS). the MIL circuit is shorted to ground (applications with a dedicated hard wire MIL circuit).
5. The MIL remains off during the instrument cluster prove out if: an indicator or instrument cluster concern is present. the MIL circuit is open (applications with a dedicated hard wire MIL circuit).
6. To turn off the MIL after a repair, a reset command from the diagnostic tool must be sent, or 3 consecutive drive cycles must be completed without a fault.
7. For all MIL concerns, go to «SYMPTOM CHARTS - GASOLINE MODELS»(/ford/five-hundred/i-2004-2007/remont/testing-diagnostics/#engine-controls-symptom-charts-except-diesel-hybrid) .
8. If the MIL flashes at a steady rate, a severe misfire condition may exist.
9. If the MIL flashes erratically, the PCM can reset while cranking if the battery voltage is low.

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.

Note. Some vehicle applications use a stand alone transmission control module (TCM). While still part of the EEC system the TCM communicates to the PCM, anti-lock brake system (ABS) module, instrument cluster, and four-wheel drive (4WD) control modules using the high speed CAN communication link. The TCM incorporates a stand alone OBD-II system. The TCM independently processes and stores fault codes, freeze frame, support PIDs as well as J1979 Mode 09 CALID and calibration verification number (CVN). The TCM does not directly illuminate the MIL, but request 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. F21 (FWD) transmission
2. ZF CFT30 (FWD) continuously variable transmission (CVT)
3. ZF 6HP26 (RWD) transmission

For additional information on these transmissions and TCM diagnostics, refer to AUTOMATIC TRANSMISSION/TRANSAXLE .

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 article 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).

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 malfunction indicator lamp (MIL), communicates to the diagnostic 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).

Modifications to OBD Vehicles

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

Multiplexing

The increased number of modules on the vehicle necessitates a more efficient method of communication. Multiplexing is a method of sending 2 or more signals simultaneously over a single circuit. In an automotive application, multiplexing is used to allow 2 or more electronic modules to communicate simultaneously over a single media. Typically this media is a twisted pair of wires. The information or messages that can be communicated on these wires consists of commands, status or data. The advantage of using multiplexing is to reduce the weight of the vehicle by reducing the number of redundant components and electrical wiring.

Multiplexing Implementation

Currently Ford Motor Company uses 2 different types of communication language protocols to communicate with the powertrain control module (PCM). These protocols are standard corporate protocol (SCP) and controller area network (CAN). For the 2005 model year the following vehicles use the SCP protocol for PCM communication with the diagnostic tool

1. Aviator
2. Excursion
3. Explorer Sport Trac
4. Ford GT
5. Freestar
6. Monterey
7. Ranger

For the 2005 model year the following vehicles use the CAN protocol for PCM communication with the diagnostic tool

1. Crown Victoria
2. E-Series
3. Escape
4. Expedition
5. Explorer
6. F-Series
7. F-Super Duty
8. Five Hundred
9. Focus
10. Freestyle
11. Grand Marquis
12. LS
13. Mariner
14. Montego
15. Mountaineer
16. Mustang
17. Navigator
18. Sable
19. Taurus
20. Thunderbird
21. Town Car

For additional information about the module communication network, refer to MODULE COMMUNICATIONS NETWORK .

Standard Corporate Protocol (SCP)

SCP is a communication language protocol based on SAE J1850 and is used by Ford Motor Company for exchanging bi-directional message (signals) between electronic modules. Two or more signals can be sent over one SCP network circuit. Ford's SCP network operates at 41.6kB/sec (kilobytes per second).

Included in these messages is diagnostic data that is output over the BUS (+) and BUS (-) lines to the data link connector (DLC). PCM connection to the DLC is typically done with a 2-wire, twisted pair cable used for network interconnection. The diagnostic data such as self-test or PIDs can be accessed with a diagnostic tool. Information on diagnostic tool equipment is described in DIAGNOSTIC METHODS - GASOLINE MODELS .

High Speed Controller Area Network (CAN)

High speed CAN is based on SAE J2284, ISO-11898 and is a serial communication language protocol used to transfer messages (signals) between electronic modules or nodes. Two or more signals can be sent over one CAN network circuit allowing 2 or more electronic modules or nodes to communicate with each other. This communication or multiplexing network operates at 500kB/sec (kilobytes per second) and allows the electronic modules to share their information messages.

Included in these messages is diagnostic data that is outputted over the CAN High (+) and CAN Low (-) lines to the data link connector (DLC). PCM connection to the DLC is typically done with a 2-wire, twisted pair cable used for the network interconnection. The diagnostic data such as self-test or PIDs can be accessed with a diagnostic tool. Information on diagnostic tool equipment is described in DIAGNOSTIC METHODS - GASOLINE MODELS .

Flash Electrically Erasable Programmable Read Only Memory (EEPROM)

The Flash EEPROM is an integrated circuit (IC) within the PCM. This IC contains the software code required by the PCM to control the powertrain. One feature of the EEPROM is that it can be electrically erased and then reprogrammed without removing the PCM from the vehicle. If a software change is required to the PCM, the module no longer needs to be replaced, but can be reprogrammed through the DLC.

Idle Air Trim

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

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

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

Once the KAM has been reset, the engine must idle for 15 minutes (actual time varies between strategies) to learn new idle air trim values. Idle quality will improve as the strategy adapts. Adaptation occurs in 4 separate modes. The modes are shown in the IDLE AIR TRIM LEARNING MODES table.

IDLE AIR TRIM LEARNING MODES

Short Term Fuel Trim

If the oxygen sensors are warmed up and the PCM determines that the engine can operate near stoichiometric air/fuel ratio (14.7:1 for gasoline), the PCM enters closed loop fuel control mode. Since an oxygen sensor can only indicate rich or lean, the fuel control strategy continuously adjusts the desired air/fuel ratio between rich and lean causing the oxygen sensor to "switch" around the stoichiometric point. If the time between rich and lean switches are the same, then the system is actually operating at stoichiometric. The desired air/fuel control parameter is called short term fuel trim (SHRTFT1 and 2) where stoichiometric is represented by 0%. Richer (more fuel) is represented by a positive number and leaner (less fuel) is represented by a negative number. Normal operating range for short term fuel trim is +/- 25%. Some calibrations will have time between switches and short term fuel trim excursions that are not equal. These unequal excursions are used to run the system slightly lean or rich of stoichiometric. This practice is referred to as using bias. For example, the fuel system can be biased slightly rich during closed loop fuel to help reduce NO x .

Values for SHRTFT1 and 2 may change significantly on a diagnostic tool as the engine is operated at different RPM and load points. This is because SHRTFT1 and 2 reacts to fuel delivery variability that changes as a function of engine RPM and load. Short term fuel trim values are not retained after the engine is turned off.

Long Term Fuel Trim

While the engine is operating in closed loop fuel control, the short term fuel trim corrections are learned by the PCM as LONGFT1 and 2 corrections. These corrections are stored in the KAM fuel trim tables. Fuel trim tables are based on engine speed and load and by bank for engines with 2 HO2S sensors forward of the catalyst. Learning the corrections in KAM improves both open loop and closed loop air/fuel ratio control. Advantages include

1. Short term fuel trim does not have to generate new corrections each time the engine goes into closed loop.
2. Long term fuel trim corrections can be used both while in open loop and closed loop modes.

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

Idle Speed Control Closed Throttle Determination (applications without Electronic Throttle Control)

One of the fundamental criteria for entering RPM control is an indication of closed throttle. Throttle mode is always calculated to the lowest learned throttle position (TP) voltage seen since engine start. This lowest learned value is called ratch, since the software acts like a one-way ratch. The ratch value (voltage) is displayed as the TPREL PID. The ratch value is relearned after every engine start. Ratch will learn the lowest, steady TP voltage seen after the engine starts. In some cases, ratch can learn higher values of TP. The time to learn the higher values is significantly longer than the time to learn the lower values. The brakes must also be applied to learn the higher values.

All PCM functions are done using this ratch voltage, including idle speed control. The PCM goes into closed throttle mode when the TP voltage is at the ratch (TPREL PID) value. An increase in TP voltage, normally less than 0.05 volts, will put the PCM in part throttle mode. Throttle mode can be viewed by looking at the TP MODE PID. With the throttle closed, the PID must read C/T (closed throttle). Slightly corrupt values of ratch can prevent the PCM from entering closed throttle mode. An incorrect part throttle indication at idle will prevent entry into closed throttle RPM control, and could result in a high idle. Ratch can be corrupted by a throttle position sensor or a circuit that drops out or is noisy, or by loose/worn throttle plates that close tight during a deceleration and spring back at a normal engine vacuum.

Fail-Safe Cooling Strategy

The fail-safe cooling strategy is activated by the PCM only in the event that an overheating condition has been identified. This strategy provides engine temperature control when the cylinder head temperature exceeds certain limits. The cylinder head temperature is measured by the cylinder head temperature (CHT) sensor. For additional information about the CHT sensor, refer to POWERTRAIN CONTROL MODULE (PCM) INPUTS for a description of the CHT sensor. Note: Not all vehicles equipped with a CHT sensor will have the fail-safe cooling strategy.

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

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

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

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

Failure Mode Effects Management

Failure mode effects management (FMEM) is an alternate system strategy in the PCM designed to maintain engine operation if one or more sensor inputs fail.

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

All FMEM sensors display a sequence error message on the diagnostic tool. The message may or may not be followed by Key On Engine Off (KOEO) or Continuous Memory DTCs when attempting Key On Engine Running (KOER) self-test mode.

Engine RPM/Vehicle Speed Limiter

The PCM will disable some or all of the fuel injectors whenever an engine RPM or vehicle over speed condition is detected. The purpose of the engine RPM or vehicle speed limiter is to prevent damage to the powertrain. The vehicle will exhibit a rough running engine condition, and the PCM will store one of the following Continuous Memory DTCs: P0219, P0297, or P1270. Once the driver reduces the excessive speed, the engine will return to the normal operating mode. No repair is required. However, the technician should clear the DTCs and inform the customer of the reason for the DTC.

Excessive wheel slippage may be caused by sand, gravel, rain, mud, snow, ice. or excessive and sudden increase in RPM while in NEUTRAL or while driving.

Powertrain Control Module (PCM)

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

VEHICLE PCM APPLICATION

PCM Locations

Note. For PCM Removal and Installation procedures, refer to ELECTRONIC ENGINE CONTROLS .

Scheme 23

1. Focus - passenger side behind the kick panel.
2. Five Hundred, Freestyle, Montego - engine compartment, driver side, mounted to the cowl.
3. Taurus, Sable, Freestar, Monterey - behind the glove compartment (access from the engine compartment dash panel) on the passenger side.
4. Mustang - front of engine compartment, passenger side, near fender, under the battery junction box.
5. Crown Victoria, Grand Marquis, Town Car - engine compartment, driver side, fender mounted.
6. LS, Thunderbird, Explorer, Mountaineer, Aviator - passenger side, near side cowl, behind the glove compartment.
7. Ford GT - engine compartment, driver side, behind the driver seat, quarter panel mounted.
8. Escape, Mariner, Explorer Sport Trac, Ranger - behind the instrument panel (cowl), center to both driver and passenger sides (access from the engine compartment).
9. Expedition, Navigator, F-Series, F-Super Duty - passenger side of the engine compartment, mounted to the cowl.
10. Excursion - lower dash panel on the driver side.
11. E-Series - engine compartment, driver side, near the cowl (access from the engine compartment).

104-PIN PCM POWER AND GROUNDS

Scheme 24

150-PIN PCM POWER AND GROUNDS

Scheme 25

150-PIN PCM POWER AND GROUNDS

Scheme 26

170-PIN PCM POWER AND GROUNDS

Scheme 27

190-PIN PCM POWER AND GROUNDS

Fuel Injector Control Module

The fuel injector control module (FICM) is used to control the dual-injection fuel delivery system for gasoline engines. Based on an input from the PCM the FICM will control either single or dual-injection modes.

Scheme 28

Fuel Pump Driver Module (FPDM)

Note. For the Thunderbird and LS, the FPDM functions are incorporated in the rear electronic module (REM). The fuel pump operation is the same as for applications using the stand-alone FPDM. The REM will, however, communicate diagnostic information through the communication link instead of using a fuel pump monitor (FPM) circuit.

Note. The Ford GT uses 2 FPDMs to control fuel for the dual-injection fuel delivery system. The PCM will output only one fuel pump duty cycle which is used by both pumps. The PCM will individually monitor the FPDMs through their fuel pump monitor circuits. Both FPDMs are mounted on the same bracket. The FPDM mounted in the upper position on the bracket is referred to as FPDM and the FPDM mounted in the lower position, is referred to as FPDM2.

The FPDM receives a duty cycle signal from the PCM and controls the fuel pump operation in relation to this duty cycle. This results in variable speed fuel pump operation. The FPDM sends diagnostic information to the PCM on the fuel pump monitor circuit. For additional information, refer to POWERTRAIN CONTROL MODULE (PCM) OUTPUTS , FUEL PUMP and POWERTRAIN CONTROL MODULE (PCM) INPUTS , FUEL PUMP MONITOR (FPM) .

Keep Alive Memory (KAM)

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

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. 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.
4. Idle speed control output signal functional.

HLOS Disabled Outputs To Default State

1. EGR solenoids.
2. No torque converter clutch lock-up.

Integrated Electronic Ignition System

The integrated electronic ignition (EI) system consists of a crankshaft position (CKP) sensor, coil pack(s), connecting wiring, and PCM. The coil on plug (COP) integrated EI system uses a separate coil for each spark plug and each coil is mounted directly onto the plug. The COP integrated EI system eliminates the need for spark plug wires but does require input from the camshaft position (CMP) sensor.

Electronic Throttle Control Reference Voltage (ETCREF)

ETCREF is a consistent positive voltage (5.0 volts +/- 0.5) supplied by the powertrain control module (PCM). ETCREF is internally bussed within the PCM and is specifically dedicated to the accelerator pedal position (APP) sensor and the electronic throttle body (ETB) throttle position (TP) sensor.

Electronic Throttle Control Return (ETCRTN)

ETCRTN is a return path for ETCREF and is internally bussed within the PCM. ETCRTN is specifically dedicated to the accelerator pedal position (APP) sensor and the electronic throttle body (ETB) throttle position (TP) sensor.

Gold Plated Pins

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

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

Keep Alive Power (KAPWR)

KAPWR provide a constant voltage input independent of ignition switch state to the PCM. This voltage is used by the PCM to maintain the keep alive memory (KAM).

Mass Air Flow (MAF) Return

The mass air flow return (MAF RTN) is a dedicated analog signal return from the MAF sensor. It serves as a ground offset for the analog voltage differential input by the MAF sensor to the PCM.

Power Ground (PWR GND)

The PWR GND circuit(s) is directly connected to the battery negative terminal. PWR GND provides a return path for the PCM VPWR circuits.

Signal Return (SIG RTN)

SIG RTN is a dedicated return path for VREF applied components.

Vehicle Buffered Power (VBPWR)

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

Vehicle Power (VPWR)

VPWR is the primary source of PCM power. VPWR is switched through the EEC power relay and is controlled by the ignition switch.

Vehicle Reference Voltage (VREF)

VREF is a consistent positive voltage (5.0 volts +/- 0.5) provided by the PCM. VREF is typically used by 3-wire sensors and some digital input signals.

Powertrain Control Module (PCM) Inputs

Note. Transmission inputs, which are not described here are discussed in the respective transmission article.

Accelerator Pedal Position (APP) Sensor

For information on the APP sensor, refer to the description for TORQUE BASED ELECTRONIC THROTTLE CONTROL (ETC) .

Air Conditioning (A/C) Cycling Switch

The A/C cycling switch may be wired to either the ACCS or ACPSW PCM input. When the A/C cycling switch opens, the PCM will turn off the A/C clutch. For information on the specific function of the A/C cycling switch, refer to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION . Also, refer to the SYSTEM WIRING DIAGRAMS for vehicle specific wiring.

If the ACCS signal is not received by the PCM, the PCM circuit will not allow the A/C to operate. For additional information, refer to POWERTRAIN CONTROL MODULE (PCM) OUTPUTS , WIDE OPEN THROTTLE A/C CUT-OFF (WAC) .

Note. Some applications do not have a dedicated (separate) input to the PCM indicating that A/C is requested. This information is received by the PCM through the communication link.

Air Conditioning Evaporator Temperature (ACET) Sensor

The ACET sensor measures the evaporator air discharge temperature. The ACET 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 PCM sources a low current 5 volts on the ACET circuit. With SIG RTN also connected to the ACET sensor, the varying resistance affects the voltage drop across the sensor terminals. As A/C evaporator air temperature changes, the varying resistance of the ACET sensor changes the voltage the PCM detects.

The ACET sensor is used to more accurately control A/C clutch cycling, improving defrost/demist performance, reduce A/C clutch cycling, etc.

A/C EVAPORATOR TEMPERATURE (ACET) SENSOR VOLTAGE AND RESISTANCE

Note. These values can vary 15 percent due to sensor and VREF variations. Voltage values were calculated for VREF = 5.0 volts.

Air Conditioning (A/C) Pressure Sensor

The A/C pressure sensor is located in the high pressure (discharge) side of the A/C system. The A/C pressure sensor provides a voltage signal to the PCM that is proportional to the A/C pressure. The PCM uses this information for A/C clutch control, fan control and idle speed control.

Scheme 29

Scheme 30

Air Conditioning (A/C) High Pressure Switch

The A/C high pressure switch is used for additional A/C system pressure control. The A/C high pressure switch is either dual function for multiple speed, relay controlled electric fan applications, or single function for all others.

For refrigerant containment control, the normally closed high pressure contacts open at a predetermined A/C pressure. This results in the A/C turning off, preventing the A/C pressure from rising to a level that would open the A/C high pressure relief valve.

For fan control, the normally open medium pressure contacts close at a predetermined A/C pressure. This grounds the ACPSW circuit input to the PCM. The PCM then turns on the high speed fan to help reduce the pressure.

For additional information, refer to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION . or the SYSTEM WIRING DIAGRAMS

Brake Pedal Position (BPP) Switch

The BPP switch is used by the PCM to disengage the transmission torque converter clutch and on some applications as an input to the idle speed control for idle quality and for vehicle speed control deactivation. Depending on the vehicle application the BPP switch can be connected to the PCM in the following manner

1. BPP switch is hard wired to the PCM supplying battery positive voltage (B+) when the vehicle brake pedal is applied.
2. BPP switch is hard wired to a module (ABS, LCM, or REM), the BPP signal is then broadcast over the data link to be received by the PCM.
3. BPP switch is hard wired to the anti-lock brake system (ABS) traction control/stability assist module. The stability module will interpret the BPP switch input along with other ABS inputs and generate an output called the driver brake application (DBA) signal. The DBA signal is than sent to the PCM and to other BPP signal users.

Note. On applications where the BPP switch is hard wired to the PCM and stop lamp circuit, if all stop lamp bulbs are burned out (open), high voltage is present at the PCM due to a pull-up resistor in the PCM. This provides fail-safe operation in the event the circuit to the stop lamp bulbs has failed.

Scheme 31

Brake Pedal Switch (BPS)/Brake Deactivator Switch

The BPS, also sometimes called the brake deactivator switch, is for vehicle speed control deactivation. A normally closed switch supplies battery positive voltage (B+) 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 BPS, along with the normally open brake pedal position (BPP) switch, are used for a brake rationality test within the PCM. The PCM misfire monitor profile learn function can be disable if a brake switch failure occurs. If one or both brake pedal inputs to the PCM did not change states when they were expected to, a diagnostic trouble code P1572 can be set by the PCM strategy.

Camshaft Position (CMP) Sensor

The CMP sensor detects the position of the camshaft. The CMP sensor identifies when piston No. 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 proper ignition coil to fire. The input circuit to the PCM is referred to as the CMP input or circuit. DTC P0340 is associated with this sensor.

Vehicles with 2 CMP sensors are equipped with variable camshaft timing (VCT). They use the second sensor to identify the position of the camshaft on bank 2 as an input to the PCM. DTC P0345 is associated with this sensor and it is referred to as CMP2.

There are 2 types of CMP sensors: the 3-pin connector Hall-effect type sensor (only used on F-150 4.2L applications) and the 2 pin connector variable reluctance type sensor used on all other vehicle applications.

Scheme 32

Scheme 33

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 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.

Scheme 34

Crankshaft Position (CKP) Sensor

The CKP sensor is a magnetic transducer mounted on the engine block or timing cover and is 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 trigger wheel has a total of 35 teeth spaced 10 degrees apart with one 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 trigger wheel, the CKP indicates crankshaft position and speed information to the PCM. By monitoring the missing tooth, the PCM uses the CKP signal to synchronize the ignition system and track the rotation of the crankshaft.

Scheme 35

Cylinder Head Temperature (CHT) Sensor

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

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so 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 CHT sensor is installed in the aluminum cylinder head and measures the metal temperature. The CHT sensor can provide complete engine temperature information and can be used to infer coolant temperature. If the CHT sensor conveys an overheating condition to the PCM, the PCM would then initiate a fail-safe cooling strategy based on information from the CHT sensor. A cooling system failure such as low coolant or coolant loss could cause an overheating condition. As a result, damage to major engine components could occur. 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 FAIL-SAFE COOLING STRATEGY .

Scheme 36

Differential Pressure Feedback EGR (DPFE) Sensor

For information on the DPFE sensor, refer to the description of the EXHAUST GAS RECIRCULATION (EGR) SYSTEMS .

Electronic Throttle Body (ETB) Position Sensor

For information on the electronic throttle body position sensor, refer to the description of the ETB in TORQUE BASED ELECTRONIC THROTTLE CONTROL (ETC) .

Engine Coolant Temperature (ECT) Sensor

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

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.

Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The ECT measures the temperature of the engine coolant. The sensor is threaded into an engine coolant passage.

Scheme 37

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 affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.

Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The EOT sensor measures the temperature of the engine oil. The sensor is typically threaded into the engine oil lubrication system. The PCM can use the EOT sensor input to determine the following

1. On variable cam timing (VCT) applications the EOT input is used to adjust the VCT control gains and logic for camshaft timing.
2. The PCM can use EOT sensor input in conjunction with other PCM inputs to determine oil degradation.
3. The PCM can use EOT sensor input to initiate a soft engine shutdown. To prevent engine damage from occurring as a result of high oil temperatures, the PCM has the ability to initiate a soft engine shutdown. Whenever engine RPM exceeds a calibrated level for a certain period of time, the PCM will begin reducing power by disabling engine cylinders.

Fuel Level Input

Note. The Ford GT will use a piezoelectric sonar type fuel level sensor. The sensor is located in the tank and the sensor signal is provided as a communications network message by the instrument cluster to the PCM.

The fuel level input (FLI) is either a hard wire signal input to the PCM from the fuel pump (FP) module or a communications network message. Most vehicle applications use a potentiometer type FLI sensor connected to a float in the FP module to determine fuel level.

Applications Using a Fuel Pump Relay for Fuel Pump On/Off Control

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

Fuel Pump Driver Module (FPDM) Applications

Note. The Ford GT uses 2 FPDMs to control fuel for the dual-injection fuel delivery system. The PCM will individually monitor both FPDMs through their FPM circuits.

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

FUEL PUMP DRIVER MODULE DUTY CYCLE SIGNALS

Fuel Rail Pressure (FRP) Sensor

The FRP sensor is a diaphragm strain gauge device in which resistance changes with pressure. The electrical resistance of a strain gauge increases as pressure increases, and the resistance decreases as the pressure decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to pressure.

Strain gauge 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 FRP sensor measures the pressure of the fuel near the fuel injectors. This signal is used by the PCM to adjust the fuel injector pulse width and meter fuel to each engine combustion cylinder.

Scheme 38

Fuel Rail Pressure Temperature (FRPT) Sensor

The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail and sends these signals to the PCM. The sensor uses the intake manifold vacuum as a reference to determine the pressure difference between the fuel rail and the intake manifold. The fuel return line to the fuel tank has been deleted in this type of fuel system. The relationship between fuel pressure and fuel temperature is used to determine the possible presence of fuel vapor in the fuel rail. Both pressure and temperature signals are used to control the speed of the fuel pump. The speed of the fuel pump sustains fuel rail pressure which preserves fuel in its liquid state. The dynamic range of the fuel injectors increase because of the higher rail pressure, which allows the injector pulse width to decrease.

Scheme 39

Fuel Rail Temperature (FRT) Sensor

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

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.

Voltage that is dropped across a fixed resistor in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The FRT sensor measures the temperature of the fuel near the fuel injectors. This signal is used by the PCM to adjust the fuel injector pulse width and meter fuel to each engine combustion cylinder.

Scheme 40

Fuel Tank Pressure (FTP) Sensor

For information on the FTP sensor, refer to the description of the EVAPORATIVE EMISSION (EVAP) SYSTEMS .

Generator Load Input (GENLI)

For information on the GENLI, refer to the description of the POWERTRAIN CONTROL MODULE (PCM) CONTROLLED CHARGING SYSTEM .

Heated Oxygen Sensor (HO2S)

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

Embedded with the sensing element is the HO2S heater. The heating element heats the sensor to a temperature of 800°C (1400°F). At approximately 300°C (600°F) the engine can enter closed loop operation. The VPWR circuit supplies voltage to the heater. The PCM will turn on the heater by providing the ground when the proper conditions occur. The heater allows the engine to enter closed loop operation sooner. The use of this heater requires the HO2S heater control to be duty cycled, to prevent damage to the heater.

Scheme 41

Intake Air Temperature (IAT) Sensor

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

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.

Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The IAT provides air temperature information to the PCM. The PCM uses the air temperature information as a correction factor in the calculation of fuel, spark, and air flow.

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

Currently there are 2 design types of IAT sensors used, a stand-alone/non-integrated type and a integrated type. Both types function the same, however the integrated type is incorporated into the mass air flow (MAF) sensor instead of being a stand alone sensor.

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

Scheme 42

Scheme 43

Intake Manifold Runner Control Monitor (IMRCM) - Electric Actuated

For information on the electronically controlled IMRCM system, refer to the description of the INTAKE AIR SYSTEMS .

Intake Manifold Runner Control Monitor (IMRCM) - Vacuum Actuated

For information on the vacuum IMRCM system, refer to the description of the INTAKE AIR SYSTEMS .

Knock Sensor (KS)

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

Scheme 44

Mass Air Flow (MAF) Sensor

The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire causes it to cool. This hot wire is maintained at 200°C (392°F) above the ambient temperature as measured by a constant cold wire. If the hot wire electronic sensing element must be replaced, then the entire assembly must be replaced. Replacing only the element may change the air flow calibration.

Scheme 45

The current required to maintain the temperature of the hot wire is proportional to the mass air flow. The MAF sensor then outputs an analog voltage signal to the PCM proportional to the intake air mass. The PCM calculates the required fuel injector pulse width in order to provide the desired air/fuel ratio. This input is also used in determining transmission electronic pressure control (EPC), shift and torque converter clutch scheduling.

Most MAF sensors have integrated bypass technology (IBT) with an integrated intake air temperature (IAT) sensor.

The MAF sensor is located between the air cleaner and the throttle body or inside the air cleaner assembly.

Scheme 46

Scheme 47

Output Shaft Speed (OSS) Sensor

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

Power Steering Pressure (PSP) Switch

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

Scheme 48

Power Steering Pressure (PSP) Sensor

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

Scheme 49

Power Take-Off (PTO) Switch and Circuits

The PTO circuit is used by the PCM to disable some of the OBD Monitors during PTO operation. The PTO switch is normally open. When the PTO unit is activated, the PTO switch is closed and battery voltage is supplied to the PTO input circuit. This indicates to the PCM that an additional load is being applied to the engine.

When the PTO unit is activated, the PCM disables some OBD monitors, which may not function reliably during PTO operation. Without the PTO circuit information to the PCM, false diagnostic trouble codes (DTCs) may be set during PTO operation. Prior to an Inspection/Maintenance test, the vehicle will have to be operated with the PTO disengaged long enough to successfully complete the OBD Monitors.

PTO Circuits Description

The 3 PTO input circuits are PTO mode, PTO engage, and PTO RPM.

The PTO engage circuit is used when the operator is requesting the PCM to check the needed inputs required to initiate the PTO engagement.

The PTO RPM circuit is used while the operator request additional engine RPM for PTO operation.

Starter Motor Request (SMR) Circuit

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

Throttle Position (TP) Sensor

The TP sensor is a rotary potentiometer sensor that provides a signal to the PCM that is linearly proportional to the throttle plate/shaft position. The sensor housing has a 3-blade electrical connector that may be gold plated. The gold plating increases corrosion resistance on terminals and increases connector durability. The TP sensor is mounted on the throttle body. As the TP sensor is rotated by the throttle shaft, 4 operating conditions are determined by the PCM from the TP. Those conditions are closed throttle (includes idle or deceleration), part throttle (includes cruise or moderate acceleration), wide open throttle (includes maximum acceleration or de-choke on crank), and throttle angle rate.

Scheme 50

Transmission Control Switch (TCS)

The TCS signals the PCM with VPWR whenever the TCS is pressed. On vehicles with this feature, the transmission control indicator lamp (TCIL) illuminates when the TCS is cycled to disengage overdrive. The operator of the vehicle controls the position of the TCS.

Scheme 51

Scheme 52

Vehicle Speed Sensor (VSS)

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

Scheme 53

Four-Wheel Drive (4WD) Mode Switch

The 4WD control module provides the PCM with an indication of 4WD Low. This input is used to adjust the shift schedule. A 5.0-volt module pull-up indicates 4WD High or 2WD.

Scheme 54

Powertrain Control Module (PCM) Outputs

Note. Transmission inputs, which are not described here are discussed in the respective transmission article.

Air Conditioning Clutch Relay (A/CCR)

Note. The PCM PIDs WAC and WACF are used to monitor the A/CCR output.

The A/CCR (may be referred to as the wide open throttle A/C cutoff [WAC] relay) is wired normally open. There is no direct electrical connection between the A/C switch or EATC module and the A/C clutch. The PCM will receive a signal indicating that A/C is requested (for some applications, this message is sent through the communications network). When A/C is requested, the PCM will check other A/C related inputs that are available (such as ACP SW, ACCS). If these inputs indicate A/C operation is OK, and the engine conditions are OK (such as coolant temperature, engine RPM, throttle position), the PCM will ground the A/CCR output, closing the relay contacts and sending voltage to the A/C clutch.

Canister Vent (CV) Solenoid

For information on the CV solenoid, refer to the description of the EVAPORATIVE EMISSION (EVAP) SYSTEMS .

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 one 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.

Scheme 55

Coil On Plug (COP)

The COP ignition operates similar to a standard coil pack ignition except each plug has one coil per plug. COP has 3 different modes of operation: engine crank, engine running, and CMP failure mode effects management (FMEM).

Scheme 56

Engine Crank/Engine Running

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

CMP FMEM

During CMP FMEM the COP ignition works the same as during engine crank. This allows the engine to operate without the PCM knowing if cylinder one is under compression or exhaust.

Electric EGR (EEGR) System

For information on the EEGR system, refer to EXHAUST GAS RECIRCULATION (EGR) SYSTEMS , ELECTRIC EGR SYSTEM (EEGR) .

EGR System Module (ESM)

For information on the ESM system, refer to EXHAUST GAS RECIRCULATION (EGR) SYSTEMS , EGR SYSTEM MODULE (ESM) .

EGR Vacuum Regulator (EVR) Solenoid

For information on the EVR solenoid, refer to EXHAUST GAS RECIRCULATION (EGR) SYSTEMS , DIFFERENTIAL PRESSURE FEEDBACK EGR (DPFE) SYSTEM .

Electric Secondary Air Injection Pump

For information on the electric secondary air injection pump, refer to the description of the SECONDARY AIR INJECTION (AIR) SYSTEMS .

Evaporative Emission (EVAP) Canister Purge Valve

For information on the EVAP canister purge valve, refer to the description of the EVAPORATIVE EMISSION (EVAP) SYSTEMS .

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).

FIVE HUNDRED/FREESTYLE/MONTEGO, CROWN VICTORIA/GRAND MARQUIS, TOWN CAR: FCV DUTY CYCLE OUTPUT FROM PCM (NEGATIVE DUTY CYCLE)

LS, THUNDERBIRD: FCV DUTY CYCLE OUTPUT FROM PCM

For relay controlled fans

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

For 3-speed fans, although the PCM output circuits are called low, medium, and high fan control (FC), cooling fan speed is controlled by a combination of these outputs. Refer to the following table.

2.0L FOCUS (with A/C) and TAURUS/SABLE: PCM FC OUTPUT STATE FOR COOLING FAN SPEEDS

2.3L ESCAPE: PCM FC OUTPUT STATE FOR COOLING FAN SPEEDS

FREESTAR, MONTEREY: PCM FC OUTPUT STATE FOR COOLING FAN SPEEDS

Fuel Cap Indicator Lamp

The fuel cap indicator lamp (FCIL) is a communications network message sent by the PCM. The PCM sends the message to illuminate the lamp when the strategy determines that there is a failure in the vapor management system due to the fuel filler cap not being sealed properly. This would be detected by the inability to pull vacuum in the fuel tank, after a fueling event.

Note. The FCIL on the Crown Victoria/Grand Marquis, Explorer Sport Trac, and Ranger is a dedicated output signal that is controlled by the PCM.

The fuel pump (FP) is a PCM output signal used to control the electric fuel pump. With the electronic engine control (EEC) power relay contacts closed, vehicle power (VPWR) is sent to the coil of the fuel pump relay. For electric fuel pump operation, the PCM grounds the FP circuit, which is connected to the coil of the fuel pump relay. This energizes the coil and closes the contacts of the relay, sending B+ through the FP PWR circuit to the electric fuel pump. When the ignition key is turned on, the electric fuel pump runs for about one second and will be turned off by the PCM if engine rotation is not detected.

Fuel Pump Driver Module (FPDM) Applications (and Applications with Fuel Pump Functions Incorporated in Rear Electronic Module)

Note. For the Thunderbird and LS, the FPDM functions are incorporated in the rear electronic module (REM). The fuel pump operation is the same as in applications using the stand-alone FPDM. However, the REM will transmit diagnostic information over the communications network instead of using a fuel pump monitor (FPM) circuit.

Note. The Ford GT uses 2 FPDMs to control fuel for the dual-injection fuel delivery system. The PCM will send one FP duty cycle which is used by both pumps.

The fuel pump (FP) signal is a duty cycle command sent from the PCM to the FPDM ( FUEL PUMP DUTY CYCLE OUTPUT FROM PCM ). The FPDM uses the FP command to operate the fuel pump at the speed requested by the PCM or to turn the pump off.

FUEL PUMP DUTY CYCLE OUTPUT FROM PCM

Note. Also refer to FUEL PUMP MONITOR (FPM) and FUEL PUMP DRIVER MODULE (FPDM) .

Fuel Injectors

For information on the fuel injectors, refer to the description of the FUEL SYSTEMS .

Fuel Pressure Regulator Control (FPRC) Solenoid

For information on the FPRC solenoid, refer to the description of the FUEL SYSTEMS .

Generator Regulator Control (GENRC)

For information on the GENRC, refer to the description of the POWERTRAIN CONTROL MODULE (PCM) CONTROLLED CHARGING SYSTEM .

High Fan Control

For information on high fan control, refer to FAN CONTROL .

Idle Air Control (IAC) Solenoid

For information on the IAC solenoid, refer to the description of the INTAKE AIR SYSTEMS .

Intake Manifold Runner Control (IMRC) - Electric Actuated

For information on the IMRC electrically actuated, refer to the description of the INTAKE AIR SYSTEMS .

Intake Manifold Runner Control (IMRC) - Vacuum Actuated

For information on the IMRC vacuum actuated, refer to the description of the INTAKE AIR SYSTEMS .

Intake Manifold Tuning Valve (IMTV)

For information on the intake manifold tuning valve (IMTV), refer to the description of the INTAKE AIR SYSTEMS .

Low Fan Control

For information on low fan control, refer to FAN CONTROL .

Medium Fan Control

For information on medium fan control, refer to FAN CONTROL .

Reverse Lamp Control (RLC)

For information on reverse lamp control, refer to EXTERIOR LIGHTING .

Secondary Air Injection Bypass Solenoid

For information on the secondary air injection bypass solenoid, refer to the description of the SECONDARY AIR INJECTION (AIR) SYSTEMS .

Transmission Control Indicator Lamp (TCIL)

The TCIL is an output signal from the PCM that controls the lamp on/off function depending on the engagement or disengagement of overdrive. Refer to the TRANSMISSION CONTROL SWITCH (TCS) .

Vapor Management Valve (VMV)

For information on the vapor management valve (EVAP canister purge valve), refer to the description of the EVAPORATIVE EMISSION (EVAP) SYSTEMS .

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

The PCM-VSO speed signal subsystem generates vehicle speed information for distribution to the vehicle's electrical/electronic modules and subsystems that require vehicle speed data. This subsystem senses the transmission output shaft speed with a sensor. The data is processed by the PCM and distributed as a hardwired signal or as a message on the vehicle communication network (SCP or high speed-CAN).

The key features of the PCM-VSO system are to

1. infer vehicle movement from the output shaft speed (OSS) sensor signal.
2. convert transmission output shaft rotational information to vehicle speed information.
3. compensate for tire size and axle ratio with a programmed calibration variable.
4. use a transfer case sensor for four wheel drive applications.
5. distribute vehicle speed information as a multiplexed message and/or an analog signal.

The signal from a non-contact shaft sensor (output shaft sensor [OSS] or transfer case shaft sensor [TCSS]) mounted on the transmission (automatic, manual, or 4WD transfer case) is sensed directly by the PCM. The PCM converts the OSS or TCSS information to 8000 pulses per mile, based on a tire and axle ratio conversion factor. This conversion factor is programmed into the PCM at the time the vehicle is assembled and can be reprogrammed in the field for servicing changes in the tire size and axle ratio. The PCM transmits the computed vehicle speed and distance traveled information to all the vehicle speed signal users on the vehicle. VSO information can be transmitted by a hard-wired interface between the vehicle speed signal user and the PCM, or by a speed and odometer data message through the vehicle communication network data link.

The PCM VSO hard-wired signal wave form is a DC square wave with a voltage level of 0 to VBAT. Typical output operating range is 1.3808 Hz per 1 km/h (2.22 Hz per mph).

Wide Open Throttle A/C Cut-Off (WAC)

Refer to the AIR CONDITIONING CLUTCH RELAY (A/CCR) .

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 powertrain control module (PCM) for proper vehicle operation and misfire detection.

Integrated Electronic Ignition (EI) System

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

1. The CKP sensor is used to indicate the crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted to the crankshaft. The CMP sensor is used by the COP integrated EI system to identify top dead center of compression of cylinder 1 to synchronize the firing of the individual coils.
2. The PCM uses the CKP signal to calculate a spark target and then fires the coil pack(s) to that target shown. The PCM uses the CMP sensor, not COP integrated EI systems to identify top dead center of compression of cylinder 1 to synchronize the firing of the individual coils.
3. The coils and coil packs receive their signal from the PCM to fire at a calculated spark target. Each coil within the pack fires 2 spark plugs at the same time. The plugs are paired so that as one fires during the compression stroke the other fires during the exhaust stroke. The next time the coil is fired the situation is reversed. The COP system fires only one spark plug per coil and only on the compression stroke. The PCM acts as an electronic switch to ground in the coil primary circuit. When the switch is closed, battery positive voltage (B+) applied to the coil primary circuit builds a magnetic field around the primary coil. When the switch opens, the power is interrupted and the primary field collapses inducing the high voltage in the secondary coil windings and the spark plug is fired. A kickback voltage spike occurs when the primary field collapses. The PCM uses this voltage spike to generate an ignition diagnostic monitor (IDM) signal. IDM communicates information by pulse width modulation in the PCM.
4. The PCM processes the CKP signal and uses it to drive the tachometer as the clean tach out (CTO) signal.

Scheme 57

Scheme 58

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 one 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.

Scheme 59

The CMP sensor used by COP integrated EI system is a magnetic transducer mounted on the engine front cover adjacent to the camshaft. By monitoring a target on the camshaft sprocket, the CMP sensor identifies cylinder one to the PCM. The COP integrated EI system uses this information to synchronize the firing of the individual coils.

Scheme 60

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

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

Scheme 61

Scheme 62

Scheme 63

The COP ignition operates similar to standard coil pack ignition except each plug has one coil per plug. COP has 3 different modes of operation: engine crank, engine running, and CMP Failure Mode Effects Management (FMEM).

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

During CMP FMEM the COP ignition works the same as during engine crank. This allows the engine to operate without the PCM knowing if cylinder one is under compression or exhaust.

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 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 reset the learned values contained in the keep alive memory (KAM) in the PCM. Refer to RESETTING THE KEEP ALIVE MEMORY (KAM) .

The 3 types of fuel systems used are

1. Returnable Fuel
2. Mechanical Returnless Fuel
3. Electronic Returnless Fuel

Returnable Fuel System

The returnable fuel system consists of a fuel tank with a reservoir, the fuel pump module, the fuel supply lines, the fuel filter(s), a Schrader valve/pressure test point, the fuel rail, the fuel injectors, and the fuel pressure regulator. Operation of the system is as follows

Scheme 64

1. The fuel delivery system uses the crankshaft position (CKP) sensor to signal the PCM that the engine is either cranking or running.
2. The fuel pump logic is defined in the Fuel System control strategy and is executed in the PCM. The PCM grounds the fuel pump relay for one second during key on and engine off. During crank the fuel pump relay is grounded as long as the PCM receives a CKP signal.
3. The fuel pump relay has a primary and a secondary circuit. The primary side is controlled by the PCM and the secondary side provides B+ to the fuel pump circuit when the relay is energized.
4. The inertia fuel shut-off (IFS) switch is used to de-energize the fuel delivery secondary circuit in the event of a collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision.
5. The fuel injector is a solenoid-operated valve that meters fuel flow to each combustion cylinder. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by length of time the fuel injector is held open. The injector is normally closed and is operated by 12-volt VPWR from the power relay. The ground signal is controlled by the PCM.
6. A pressure test point valve (Schrader valve) is located on the fuel rail. This is used to measure the fuel injector supply pressure for repair and diagnostic procedures. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit #134-R0087 or equivalent.
7. The fuel pressure regulator, also referred to as the pulse damper, is mounted to the fuel pump bracket within the fuel tank. It regulates fuel pressure supplied to fuel injectors. (Scheme 64)Balancing one side of the diaphragm with manifold vacuum maintains a constant fuel pressure drop across the fuel injectors. Fuel pressure is high when engine vacuum is low. Excess fuel is bypassed through the fuel pressure regulator and returned through the fuel return line to the fuel tank.
8. There are 4 filtering or screening devices in the fuel delivery system. The fuel intake sock or screen is a fine, nylon mesh mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. A fuel filter/screen is located in the inlet side of the fuel pressure regulator. The fuel filter assembly is located between the fuel pump and the pressure test point/Schrader valve.
9. The fuel pump (FP) module is a device that contains both the fuel pump and the fuel sender assembly. The fuel pump is located inside the reservoir and supplies fuel through the fuel pump module manifold to the engine and the fuel pump module jet pump.

Note. Some vehicles have the relay located in the battery junction box.

Scheme 65

Mechanical Returnless Fuel System

The mechanical returnless fuel system consists of a fuel tank with reservoir, the fuel pump, the fuel pressure regulator, the fuel filter, the fuel supply line, the fuel rail, the fuel rail pulse damper (if equipped), fuel injectors, and a Schrader valve/pressure test point. Operation of the system is as follows

Scheme 66

1. The fuel delivery system is enabled during crank or running mode once the PCM receives a crankshaft position (CKP) sensor signal.
2. The fuel pump logic is defined in the fuel system control strategy and is executed by the PCM.
3. The PCM grounds the fuel pump relay, which provides power to the fuel pump.
4. The inertia fuel shut-off (IFS) switch is used to de-energize the fuel delivery secondary circuit in the event of collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision.
5. A pressure test point valve (Schrader valve) is located on the fuel rail and is used to measure the fuel injector supply pressure for diagnostic procedures and repairs. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit #134-R0087 or equivalent.
6. A pulse damper is located on the fuel rail (if equipped). The pulse damper reduces the fuel system noise caused by the pulsing of the fuel injectors. The vacuum port located on the damper is connected to manifold vacuum to avoid fuel spillage if the pulse damper diaphragm ruptures (the pulse damper should not be confused with a fuel pressure regulator).
7. The fuel injector is a solenoid-operated valve that meters the fuel flow to each combustion cylinder. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open. The injector is normally closed and is operated by 12-volt VPWR from the power relay. The ground signal is controlled by the PCM.
8. There are 3 filtering or screening devices in the fuel delivery system. The intake sock is a fine, nylon mesh screen mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. The fuel filter assembly is located between the fuel pump and the pressure test point/Schrader valve.
9. The fuel pump (FP) module contains the fuel pump, the fuel pressure regulator and the fuel sender assembly. The fuel pressure regulator is attached to the fuel pump in the fuel pump module located in the fuel tank. It regulates the fuel pressure supplied to the fuel injectors. The fuel pressure regulator is a diaphragm-operated relief valve. Fuel pressure is established by a spring preload applied to the diaphragm. Excess fuel is bypassed through the regulator and returned to the fuel tank.

Electronic Returnless Fuel System

The electronic returnless fuel system consists of a fuel tank with reservoir, the fuel pump, the fuel rail pressure (FRP) sensor, the fuel filter, the fuel supply line, the fuel rail temperature (FRT) sensor, the fuel rail, the fuel injectors, and a Schrader valve/pressure test point. Operation of the system is as follows

Scheme 67

1. The fuel delivery system is enabled during crank or running mode once the PCM receives a crankshaft position (CKP) sensor signal.
2. The fuel pump logic is defined in the fuel system control strategy and is executed by the PCM.
3. The PCM commands a duty cycle to the fuel pump driver module (FPDM).
4. The FPDM modulates the voltage to the fuel pump (FP) required to achieve the proper fuel pressure. Voltage for the fuel pump is supplied by the power relay or FPDM power supply relay. (For additional information on FPDM operation, refer to «FUEL PUMP»(/ford/five-hundred/i-2004-2007/remont/testing-diagnostics/#engine-controls-description-operation-except-diesel-hybrid) and «FUEL PUMP MONITOR (FPM)»(/ford/five-hundred/i-2004-2007/remont/testing-diagnostics/#engine-controls-description-operation-except-diesel-hybrid) .)
5. The fuel rail pressure (FRP) sensor provides the PCM with the current fuel rail pressure. The PCM uses this information to vary the duty cycle output to the FPDM to compensate for varying loads.
6. The fuel rail temperature (FRT) sensor measures the current fuel temperatures in the fuel rail. This information is used to vary the fuel pressure and avoid fuel system vaporization.
7. The fuel injector is a solenoid-operated valve that meters the fuel flow to each combustion cylinder. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open. The injector is normally closed and is operated by 12-volt VPWR from the power relay. The ground signal is controlled by the PCM.
8. A pressure test point valve (Schrader valve) is located on the fuel rail and is used to measure the fuel injector supply pressure for diagnostic procedures and repairs. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit #134-R0087 or equivalent.
9. There are 3 filtering or screening devices in the fuel delivery system. The intake sock is a fine, nylon mesh screen mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. The fuel filter assembly is located between the fuel pump and the pressure test point/Schrader valve.
10. The fuel pump (FP) module is a device that contains the fuel pump and the fuel sender assembly. The fuel pump is located inside the reservoir and supplies fuel through the fuel pump module manifold to the engine and the fuel pump module jet pump.
11. The inertia fuel shut-off (IFS) switch is used to de-energize the fuel delivery secondary circuit in the event of a collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision.

Scheme 68

Fuel Pump Module and Reservoir

The fuel pump module is mounted inside the fuel tank in a reservoir. The pump has a discharge check valve that maintains the system pressure after the ignition key has been turned off to minimize starting concerns. The reservoir prevents fuel flow interruptions during extreme vehicle maneuvers with low tank fill levels.

Scheme 69

Fuel Pump Module

The fuel pump (FP) module is a device that contains the fuel pump and sender assembly. The fuel pump is located inside the FP module reservoir and supplies fuel through the FP module manifold to the engine and FP module jet pump. The jet pump continuously refills the reservoir with fuel, and a check valve located in the manifold outlet maintains system pressure when the fuel pump is not energized. A flapper valve located in the bottom of the reservoir allows fuel to enter the reservoir and prime the fuel pump during the initial fill.

Scheme 70

Scheme 71

Scheme 72

Fuel Filters

The system contains 4 filtering or screening devices. Refer to the individual component illustrations for locations.

1. The fuel intake sock or screen is a fine nylon mesh sock mounted on the intake side of the fuel pump. It is part of the assembly and cannot be repaired separately.
2. The filter/screen at the fuel rail port of the injectors is part of the fuel injector assembly and cannot be repaired separately.
3. The filter/screen at fuel inlet side of the fuel pressure regulator is part of the regulator assembly and cannot be repaired separately.
4. The fuel filter assembly is located between the fuel pump (tank) and the pressure test point (Schrader valve) or injectors. This filter may be replaced.

Pressure Test Point

On some applications there is a pressure test point with a Schrader fitting in the fuel rail that relieves the fuel pressure and measures the fuel injector supply pressure for repair and diagnostic procedures. Before repairing or testing the fuel system, read any WARNING, CAUTION, and HANDLING information. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit #134-R0087 or equivalent.

Fuel Injector

The fuel injector is a solenoid-operated valve that meters fuel flow to the engine. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open.

The fuel injector is normally closed, and is operated by 12-volt VPWR from the electronic engine control power relay. The ground signal is controlled by the PCM.

The injector is the deposit resistant injection (DRI) type and does not have to be cleaned. However, it can be flow checked and, if found outside of specification, the fuel injector should be replaced.

Scheme 73

Fuel Pressure Regulator

The fuel pressure regulator is attached to the fuel rail downstream of the fuel injectors. It regulates the fuel pressure supplied to the fuel injectors. The regulator is a diaphragm-operated relief valve. One side of the diaphragm senses the fuel pressure and the other side is connected to the intake manifold vacuum. Fuel pressure is established by a spring preload applied to the diaphragm. Balancing one side of the diaphragm with manifold vacuum maintains a constant fuel pressure drop across the fuel injectors. Fuel pressure is high when engine vacuum is low. Excess fuel is bypassed through the fuel pressure regulator and returned through the fuel return line to the fuel tank.

Scheme 74

Fuel Rail Pulse Damper

The fuel rail pulse damper is located on the fuel rail and reduces the fuel system noise caused by the pulsing of the fuel injectors. The vacuum port located on the damper is connected to manifold vacuum to avoid fuel spillage if the pulse damper diaphragm ruptures. (The fuel rail pulse damper should not be confused with a fuel pressure regulator; it does not regulate the fuel rail pressure.)

Inertia Fuel Shutoff (IFS) Switch

The inertia fuel shutoff (IFS) switch is used in conjunction with the electric fuel pump. The purpose of the IFS switch is to shutoff the fuel pump if a collision occurs. It consists of a steel ball held in place by a magnet. When a sharp impact occurs, the ball breaks loose from the magnet, rolls up a conical ramp and strikes a target plate which opens the electrical contacts of the switch and shuts off the electric fuel pump. Once the switch is open, it must be manually reset before restarting the vehicle. Refer to the Owner's Literature for the location of the IFS.

Scheme 75

The EGR system controls the 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 reduced, lowering NOx emissions.

Differential Pressure Feedback EGR (DPFE) System

The differential pressure feedback EGR system consists of a differential pressure feedback EGR sensor, EGR vacuum regulator (EVR) solenoid, EGR valve, orifice tube assembly, powertrain control module (PCM), and connecting wires and vacuum hoses. Operation of the system is as follows

1. The DPFE system receives signals from the engine coolant temperature (ECT) sensor or cylinder head temperature (CHT) sensor, intake air temperature (IAT) sensor, throttle position (TP) sensor, mass air flow (MAF) sensor, and crankshaft position (CKP) 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 EGR system is activated. The PCM deactivates EGR during idle, extended wide open throttle, or whenever a failure is detected in an EGR component or EGR required input.
2. The PCM calculates the desired amount of EGR flow for a given engine condition. It then determines the desired pressure drop across the metering orifice required to achieve that flow and outputs the corresponding signal to the EVR solenoid.
3. The EVR solenoid receives a variable duty cycle signal (0 to 100%). The higher the duty cycle the more vacuum the solenoid diverts to the EGR valve.
4. The increase in vacuum acting on the EGR valve diaphragm overcomes the valve spring and begins to lift the EGR valve pintle off its seat, causing exhaust gas to flow into the intake manifold.
5. Exhaust gas flowing through the EGR valve must first pass through the EGR metering orifice. With one side of the orifice exposed to exhaust backpressure and the other to the intake manifold, a pressure drop is created across the orifice whenever there is EGR flow. When the EGR valve closes, there is no longer flow across the metering orifice and pressure on both sides of the orifice is the same. The PCM constantly targets a desired pressure drop across the metering orifice to achieve the desired EGR flow.
6. The DPFE sensor measures the actual pressure drop across the metering orifice and relays a proportional voltage signal (0 to 5 volts) to the PCM. The PCM uses this feedback signal to correct for any errors in achieving the desired EGR flow.

Scheme 76

The DPFE 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 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 that 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.

Scheme 77

Tube Mounted Differential Pressure Feedback EGR (DPFE) Sensor

The tube mounted DPFE sensor is identical in operation as the larger plastic DPFE sensors and uses a 1.0 volt offset. The HI and REF hose connections are marked on the side of the sensor.

Scheme 78

The EVR solenoid is an electromagnetic device which is 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 atmosphere. Note that at 0% duty cycle (no electrical signal applied), the EVR solenoid allows some vacuum to pass, but not enough to open the EGR valve.

Scheme 79

Scheme 80

EGR VACUUM REGULATOR (EVR) SOLENOID DATA

Exhaust Gas Recirculation (EGR) Valve

The EGR valve in the DPFE system is a conventional, vacuum-actuated. The valve increases or decreases the flow of exhaust gas recirculation. 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 (4.5 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.

Scheme 81

Scheme 82

Orifice Tube Assembly

The 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 DPFE sensor which provides feedback to the PCM.

Scheme 83

Highlights of the EEGR System

1. The EEGR valve is activated by an electric stepper motor and does not use vacuum to control the physical movement of the valve.
2. No vacuum diaphragm is used.
3. No DPFE sensor is used.
4. No orifice tube/assembly is used.
5. No EGR EVR solenoid is used.
6. Engine coolant is routed through the assembly.

The EEGR system uses exhaust gas recirculation to control the oxides of nitrogen (NOx) emissions just like vacuum operated systems. The only difference is the way in which the exhaust gas is controlled.

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

Scheme 84

1. The EEGR system receives signals from the engine coolant temperature (ECT) or cylinder head temperature (CHT) sensor, throttle position (TP) sensor, mass air flow (MAF) sensor, crankshaft position (CKP) sensor, and the manifold absolute pressure (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 will deactivate the EEGR during idle, extended wide open throttle, or whenever a failure is detected in an EEGR component or EGR required input. The EEGR system receives signals from the engine coolant temperature (ECT) or cylinder head temperature (CHT) sensor, throttle position (TP) sensor, mass air flow (MAF) sensor, crankshaft position (CKP) sensor, and the manifold absolute pressure (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 will deactivate the EEGR during idle, extended wide open throttle, or whenever a failure is detected in an EEGR component or EGR required input. The PCM calculates the desired amount of EGR for a given set of engine operating conditions. The PCM in turn will output signals to the EEGR motor to move (advance or retract) a calibrated number of discrete steps. The electric stepper motor will directly actuate 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. 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 will correlate to the MAP signal (increasing EGR will increase manifold pressure values).

Hardware

The EEGR valve is a water cooled motor/valve assembly. The motor is commanded to move in 52 discrete steps as it acts directly on the EEGR valve. The position of the valve determines the rate of EGR. The built in spring works to close the valve (against the motor opening force).

Scheme 85

The ESM is an updated DPFE EGR system. It functions in the same manner as the conventional DPFE system, however 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 measuring 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). The system provides the PCM with a differential DPFE signal, identical to a traditional DPFE system.

The delta pressure feedback EGR monitor is comprised of a series of electrical tests and functional tests that monitor various aspects of the EGR system operation.

First, the DPFE sensor input circuit is checked for out of range values (P1400/P0405 P1401/P0406). The EVR output circuit is checked for opens and shorts (P1409/P0403).

Note. EGR normally has large amounts of water vapor that are the result of the engine combustion process. During cold ambient temperatures, under some circumstances, water vapor can freeze in the DPFE sensor, hoses, as well as other components in the EGR system. In order to prevent MIL illumination for temporary freezing, the following logic is used.

If an EGR system malfunction is detected below 0°C (32°F), only the EGR system is disabled for the current driving cycle. A DTC is not stored and the I/M readiness status for the EGR monitor will not change. The EGR monitor will, however, continue to operate. If the EGR monitor determines that the malfunction is no longer present, the EGR system will be enabled and normal system operation will be restored.

If an EGR system malfunction is detected above 0°C (32°F), the EGR system and the EGR monitor is disabled for the current driving cycle. A DTC is stored and the MIL is illuminated if the malfunction has been detected on 2 consecutive driving cycles.

After the vehicle has warmed up and normal EGR rates are being commanded by the PCM, the low flow check is carried out. Since the EGR system is a closed loop system, the EGR system will deliver the requested EGR flow as long as it has the capability to do so. If the EVR duty cycle is very high (greater than 80% duty cycle), the differential pressure indicated by the DPFE sensor is evaluated to determine the amount of EGR system restriction. If the differential pressure is below a calibrated threshold, a low flow malfunction is indicated (P0401/P0406).

Finally, the differential pressure indicated by the DPFE sensor is also checked at idle with zero requested EGR flow to carry out the high flow check. If the differential pressure exceeds a calibrated limit, it indicates a stuck open EGR valve or debris temporarily lodged under the EGR valve seat (P0402).

If the inferred ambient temperature is less than 0°C (32°F), or greater than 60°C (140°F), or the altitude is greater than 8,000 feet (BARO less than 22.5 in-Hg), the EGR monitor cannot be run reliably. In these conditions, a timer starts to accumulate the time in these conditions. If the vehicle leaves these extreme conditions, the timer starts to decrement, and, if conditions permit, will attempt to complete the EGR flow monitor. If the timer reaches 800 seconds, the EGR monitor is disabled for the remainder of the current driving cycle and the EGR Monitor I/M Readiness bit will be set to a ready condition after one such driving cycle. Vehicles will require 2 such driving cycles for the EGR monitor to be set to a ready condition.

Scheme 86

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 OBD regulations use the enhanced EVAP system. Some applications also incorporate an on-board refueling vapor recovery (ORVR) system. Refer to EVAPORATIVE EMISSIONS for vehicle specific information.

Enhanced Evaporative Emission (EVAP) System

The enhanced EVAP system consists of a fuel tank, fuel filler cap, fuel tank mounted or in-line fuel vapor control valve, fuel vapor vent valve, EVAP canister, fuel tank mounted or fuel pump mounted or in-line fuel tank pressure (FTP) sensor, EVAP canister purge valve or vapor management valve (VMV), intake manifold hose assembly, EVAP canister vent (CV) solenoid, powertrain control module (PCM) and connecting wires, and fuel vapor hoses.

Scheme 87

1. The enhanced EVAP system uses inputs from the engine coolant temperature (ECT) sensor or cylinder head temperature (CHT) sensor, the intake air temperature (IAT) sensor, the mass air flow (MAF) sensor, the vehicle speed and the FTP sensor to provide information about engine operating conditions to the PCM. The fuel level input (FLI) and FTP sensor signals to the PCM are used by the PCM to determine activation of the EVAP leak check monitor based on the presence of vapor generation or fuel sloshing.
2. The PCM determines the desired amount of purge vapor flow to the intake manifold for a given engine condition. The PCM can then output the required signal to the EVAP canister purge valve or VMV. The PCM uses the enhanced EVAP system inputs to evacuate the system using the EVAP canister purge valve or VMV, seals the enhanced EVAP system from the atmosphere using the CV solenoid, and uses the FTP sensor to observe total vacuum lost for a period of time.
3. The CV solenoid seals the enhanced EVAP system to atmosphere during the EVAP leak check monitor.
4. The PCM outputs a variable duty cycle signal (between 0% and 100%) to the solenoid on the EVAP canister purge valve or VMV. On applications with electronic EVAP canister purge valve or VMV, the PCM outputs a variable current (between 0 mA and 1,000 mA).
5. The FTP sensor monitors the fuel tank pressure during engine operation and continuously transmits an input signal to the PCM. During the EVAP monitor testing, the FTP sensor monitors the fuel tank pressure or vacuum bleed-up.
6. The fuel tank mounted fuel vapor vent valve assembly and the fuel tank mounted fuel vapor control valve (or remote fuel vapor control valve) are used in the enhanced EVAP system to control the flow of fuel vapor entering the engine. All of these valves also prevent fuel tank overfilling during refueling operation and prevent liquid fuel from entering the EVAP canister and the EVAP canister purge valve or VMV under any vehicle altitude, handling, or rollover condition.
7. The enhanced EVAP system, including all the fuel vapor hoses, can be checked when a leak is detected by the PCM. Refer to EVAPORATIVE EMISSIONS for information on leak detection tools and procedures.

EVAP Canister Purge Valve

Note. The EVAP canister purge valve may also be referred to as a vapor management valve (VMV).

The EVAP canister purge valve is part of the enhanced EVAP system that is 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 electronic EVAP canister purge valve controls the flow of vapors electronically by way of a solenoid thereby, eliminating the need for an electronic vacuum regulator and vacuum diaphragm. The PCM outputs a signal between 0% and 100% duty cycle to control the EVAP canister purge valve. On applications with an electronic EVAP canister purge valve, the PCM outputs a signal between 0 mA and 1,000 mA to control the solenoid.

Scheme 88

Scheme 89

The FTP sensor or in-line FTP sensor is used to measure the fuel tank pressure during the EVAP leak check monitor.

Scheme 90

Scheme 91

During the 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.

Scheme 92

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 repaired or replaced as an individual component. The intake air system also contains a sensor that measures the intake air temperature (IAT), and which may also be integrated with the MAF sensor. (Refer to POWERTRAIN CONTROL MODULE (PCM) INPUTS for additional information on the MAF and IAT sensors.) Air induction resonators can be separate components or 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 throttle body assembly with hoses.

Scheme 93

There are 3 basic types of intake air sub-systems

1. Intake Manifold Runner Control (IMRC) electric actuated system
2. Intake Manifold Runner Control (IMRC) vacuum actuated system
3. Tuning Valve (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).

Systems designed to control charge motion are defined to be intake manifold runner controls. Intake manifold runner control systems generally have to modify spark when the systems are active because altering the charge motion affects the burn rate within the cylinder.

Systems designed to control intake manifold dynamics or tuning are defined to be intake manifold tuning valves. Intake manifold tuning systems generally do not require any changes to spark or air/fuel ratio because these systems only alter the amount of airflow entering the engine.

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) will not use an idle air control (IAC).

Intake Manifold Runner Control (IMRC) Electric Actuated System

The IMRC electric actuated system consists of a remote mounted motorized actuator with an attaching linkage for each housing on each bank. The linkage attaches to the housing butterfly plate levers. Some variations can have either 2 intake air passages for each cylinder with one passageway that is always open and the other is opened and closed with a butterfly valve plate. The other type has a butterfly valve with a small passageway that opens up into a larger size orifice when the butterfly plates are opened. The butterfly valve plates are opened and closed by an electric motor and the motorized actuator houses an internal switch or switches, depending on the application, to provide feedback to PCM indicating the butterfly valve plate position. If the IMRC system is not working correctly then a DTC will be set.

Below approximately 3,000 RPM, the motorized actuator will not be energized. This will allow the linkage to fully extend and the butterfly valve plates to remain closed. Above approximately 3,000 RPM the motorized actuator will be energized. The attaching linkage will pull the butterfly valve plates into the open position. Some vehicles will activate the IMRC near 1,500 RPM.

Scheme 94

1. The PCM uses the throttle position (TP) sensor and crankshaft position (CKP) signals to determine activation of the IMRC system. There must be a positive change in voltage from the TP sensor along with the increase in RPM to open the valve plates.
2. The PCM uses the information from the input signals to control the IMRC motorized actuator based upon RPM and changes in the throttle position.
3. The PCM energizes the actuator to open the butterfly plates.
4. The IMRC housing contains butterfly plates to allow increased air flow.

Intake Manifold Runner Control (IMRC) Vacuum Actuated System

The IMRC vacuum actuated system consists of a manifold mounted vacuum actuator and a PCM controlled electric solenoid. The linkage from the actuator attaches to the manifold butterfly plate lever. The IMRC actuator and manifold are composite/plastic with a single intake air passage for each cylinder. The passage has a butterfly valve plate that blocks a large percentage of the opening when actuated, leaving the top of the passage open to generate turbulence. The housing uses a return spring to hold the butterfly valve plates open. The vacuum actuator houses an internal monitor circuit to provide feedback to the PCM indicating the butterfly valve plate position.

Below approximately 3,000 RPM, the vacuum solenoid is energized. This allows manifold vacuum to be applied and the butterfly valve plates to remain closed. Above approximately 3,000 RPM, the vacuum solenoid is de-energized. This allows vacuum to vent from the actuator and the butterfly valve plates to open.

Scheme 95

1. The PCM monitors the TP sensor, CHT, and CKP signals to determine activation of the IMRC system. There must be a positive change in voltage from the TP sensor along with the increase in RPM at the proper engine temperature to open the valve plates.
2. The PCM uses the information from the input signals to control the IMRC electric solenoid based upon changes in the throttle position, the engine temperature, and the RPM.
3. The PCM energizes the solenoid with the key on and the engine running. Vacuum is then applied to the actuator to pull the butterfly plates closed.

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

The motorized IMTV unit is not energized below approximately 2,600 RPM. The shutter is in the closed position not allowing airflow blend to occur in the intake manifold. Above approximately 2,600 RPM the motorized unit is energized. The motorized unit is commanded on by the PCM initially at a 100 percent duty cycle to move the shutter to the open position, and then falling to approximately 50 percent to continue to hold the shutter open.

Scheme 96

1. The PCM uses the TP sensor and CKP signals to determine activation of the IMTV system. There must be a positive change in voltage from the TP sensor along with the increase in RPM to open the shutter.
2. The PCM uses the information from the input signals to control the IMTV.
3. When commanded on by the PCM, the motorized actuator shutter opens up the end of the vertical separating wall at high engine speeds to allow both sides of the manifold to blend together.

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) .

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 PCM to maintain the proper 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.

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

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.

The TP sensor monitors the throttle position and provides an electrical signal to the PCM. It is monitored by the OBD system for component integrity, system functionality, and faults that can cause emissions levels to exceed the standards set by government regulations. For additional information on the TP sensor, refer to THROTTLE POSITION (TP) SENSOR .

Idle Air Control (IAC) Valve (Applications Without ETC)

The IAC valve assembly controls the engine idle speed and provides a dashpot function. The IAC valve assembly meters intake air around the throttle plate through a bypass within the IAC valve assembly and throttle body. The PCM determines the desired idle speed or bypass air and signals the IAC valve assembly through a specified duty cycle. The IAC valve responds by positioning the IAC valve to control the amount of bypassed air. The PCM monitors engine RPM and increases or decreases the IAC duty cycle in order to achieve the desired RPM.

Note. The IAC valve assembly is NOT ADJUSTABLE and CANNOT BE CLEANED, also some IAC valves are normally open and others are normally closed. Some IAC valves require engine vacuum to operate.

The PCM uses the IAC valve assembly to control

1. No touch start.
2. Cold engine fast idle for rapid warm-up.
3. Idle (corrects for engine load).
4. Stumble or stalling on deceleration (provides a dashpot function).
5. Over-temperature idle boost.

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.

Features of the Throttle Body Assembly include

1. Idle air control (IAC) valve assembly mounted directly to the throttle body assembly (some vehicles).
2. A pre-set stop to locate the WOT position.
3. An air supply channel upstream of the throttle plate to provide fresh air to the PCV system (some vehicles only).
4. Individual vacuum taps for PCV, EGR, EVAP and miscellaneous control signals (some vehicles only).
5. PCV air return (if applicable).
6. A throttle body-mounted TP sensor.
7. A sealant/coating on the throttle bore and throttle plate makes the throttle body air flow tolerant to engine intake sludge accumulation. These throttle body assemblies MUST NOT BE CLEANED and have a white/black attention decal advising not to clean.
8. A non-adjustable stop screw for close plate idle air flow.

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.

Electric Secondary AIR System

The electric secondary AIR system consists of an electric AIR pump, single or dual combination check air injection diverter (AIR diverter) valve(s), an AIR bypass solenoid, an AIR relay, a powertrain control module (PCM) and connecting wires, and vacuum hoses.

Scheme 97

1. The PCM requires cylinder head temperature (CHT), intake air temperature (IAT), and crankshaft position (CKP) inputs to initiate the secondary air injection function.
2. When the engine is started, the strategy will determine when to enable the electric AIR pump. The PCM signals the AIR relay and the AIR bypass solenoid, after a (5 to 15) second delay, to begin system operation. Once the catalyst is lit-off, the PCM then signals the AIR relay to stop AIR pump operation and to close the AIR bypass solenoid from supplying vacuum to the AIR diverter valve(s).
3. The AIR relay provides the start-up signal and will switch the high current required to operate the AIR pump.
4. The AIR bypass solenoid applies a vacuum to the AIR diverter valve(s) causing it to open and to allow air to flow into the exhaust manifolds.
5. The function of the water shield, (if equipped), is to provide the AIR pump with a source of dry air.
6. The electric AIR pump delivers the required amount of air to control emissions during engine operation. Air is forced into the exhaust manifolds to oxidize the hydrocarbons and carbon monoxide created by running rich at start up.

Electric AIR Pump

The electric AIR pump provides pressurized air to the secondary AIR system. The electric AIR pump functions independently of RPM and is controlled by the PCM. The electric AIR pump is only used for short periods of time. Delivery of air is dependent on the amount of system backpressure and system voltage. The inlet system of the AIR pump incorporates a splash cap which helps to guard against dirt and water.

Scheme 98

AIR Bypass Solenoid

The secondary AIR bypass solenoid is used by the PCM to control vacuum to the secondary air injection diverter (AIR diverter) valve. The AIR bypass solenoid is a normally closed solenoid. The AIR bypass solenoid also has a filtered vent feature to permit vacuum release.

Scheme 99

AIR Diverter Valve

The secondary AIR diverter valve is used with the electric AIR pump to provide on/off control of air to the exhaust manifold and catalytic converter. When the electric AIR pump is on and vacuum is supplied to the AIR diverter valve, air passes the integral check valve disk. When the electric AIR pump is off, and vacuum is removed from the AIR diverter valve, the integral check valve disk is held on the seat and stops air from being drawn into the exhaust system and prevents the back flow of the exhaust into the secondary AIR system.

Scheme 100

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, and default mode. At idle and low engine speeds with closed throttle, the 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

Variable Cam Timing (VCT) System

The VCT system consists of an electric hydraulic positioning control solenoid, a camshaft position (CMP) sensor, and a trigger wheel. The CMP trigger wheel has a number of equally spaced teeth equal to the number (n) of cylinders on a bank plus one extra tooth (n+1). Four cylinder and V8 engines use a CMP 4+1 tooth trigger wheel. V6 engines use a CMP 3+1 tooth trigger wheel. The extra tooth placed between the equally spaced teeth represents the CMP signal for that bank. A crankshaft position sensor (CKP) provides the PCM with crankshaft positioning information in 10 degree increments.

Scheme 101

1. The PCM receives input signals from the intake air temperature (IAT) sensor, engine coolant temperature (ECT) sensor, engine oil temperature (EOT) sensor, CMP, throttle position (TP) sensor, mass air flow (MAF) sensor, and CKP to determine the operating conditions of the engine. At idle and low engine speeds with closed throttle, the PCM controls the camshaft position based on ECT, EOT, IAT, and MAF. During part and wide open throttle, the camshaft position is determined by engine RPM, load and throttle position. The VCT system will not operate until the engine is at normal operating temperature.
2. The VCT system is enabled by the PCM when the proper conditions are met.
3. The CKP signal is used as a reference for CMP positioning.
4. The VCT solenoid valve is an integral part of the VCT system. The solenoid valve controls the flow of engine oil in the VCT actuator assembly. As the PCM controls the duty cycle of the solenoid valve, oil pressure/flow advances or retards the cam timing. Duty cycles near 0% or 100% represent rapid movement of the camshaft. Retaining a fixed camshaft position is accomplished by dithering (oscillating) the solenoid valve duty cycle. The PCM calculates and determines the desired camshaft position. It will continually update the VCT solenoid duty cycle until the desired position is achieved. A difference between the desired and actual camshaft position represents a position error in the PCM VCT control loop. The PCM will disable the VCT and place the camshaft in a default position if a fault is detected. A related DTC will also be set when the fault is detected.
5. When the VCT solenoid is energized, engine oil is allowed to flow to the VCT actuator assembly which advances or retards the cam timing. One half of the VCT actuator is coupled to the camshaft and the other half is connected to the timing chain. Oil chambers between the 2 halves couple the camshaft to the timing chain. When the flow of oil is shifted from one side of the chamber to the other, the differential change in oil pressure forces the camshaft to rotate in either a advance or retard position depending on the oil flow.

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.

Currently, Ford uses both heated and non-heated PCV systems. 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 or the PCV tube to prevent the valve or tube from freezing. The valve or the tube heater can be controlled by either the 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.

Heated Tubes

1. PCM controlled (no thermistor in harness)
2. Non-PCM controlled (thermistor in harness)

PCV Valves

1. Non-heated
2. Water heated
3. Non-PCM controlled electrically heated thermistor in harness
4. PCM controlled

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

Note. PCV systems that comply with OBD PCV monitoring requirements will 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 .

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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). 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, 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 will be used between the front and rear exhaust pipes. Catalytic converter efficiency is monitored by the on-board diagnostic (OBD) system strategy in the PCM. For information on the OBD catalyst monitor, refer to the description for the CATALYST EFFICIENCY MONITOR .

The number of HO2S used in the exhaust stream and the location of these sensors depend on the vehicle emission certification level (i.e. LEV, ULEV, PZEV). On most vehicles only 2 HO2S are used in an exhaust stream. The front sensors (HO2S11/HO2S21) before the catalyst will be used for primary fuel control while the ones after the catalyst (HO2S12/HO2S22) will be used to monitor catalyst efficiency. However, some partial zero emission vehicles (PZEV) will use 3 HO2S sensors 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). Current PZEV vehicles use only a 4-cylinder engine, so only the Bank 1 HO2S will be used.

Scheme 108

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Catalytic Converter

A catalyst is a material that remains unchanged when it initiates and increases the speed of a chemical reaction. A catalyst will also enable a chemical reaction to occur at a lower temperature. The concentration of exhaust gas products released to the atmosphere must be controlled. The catalytic converter assists in this task. It contains a catalyst in the form of a specially treated ceramic honeycomb structure saturated with catalytically active precious metals. As the exhaust gases come in contact with the catalyst, they are changed into mostly harmless products. The catalyst initiates and speeds up heat producing chemical reactions of the exhaust gas components so they are used up as much as possible.

Light Off Catalyst

As the catalyst heats up, converter efficiency rises rapidly. The point at which conversion efficiency exceeds 50% is called catalyst light off. For most catalysts this point occurs at 246°C to 301°C (475°F to 575°F). A fast light catalyst is a 3-way catalyst (TWC) that is located as close to the exhaust manifold as possible. Because the light off catalyst is located close to the exhaust manifold it will light off faster and reduce emissions quicker than the catalyst located under the body. Once the catalyst lights off, the catalyst will quickly reach the maximum conversion efficiency for that catalyst.

Three-Way Catalyst (TWC) Conversion Efficiency

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

Scheme 110

Exhaust System

The purpose of the exhaust system is to convey engine emissions from the exhaust manifold to the atmosphere. Engine exhaust emissions are directed from the engine exhaust manifold to the catalytic converter through the front exhaust pipe. An HO2S is mounted on the front exhaust pipe before the catalyst. The catalytic converter reduces the concentration of carbon monoxide (CO), unburned hydrocarbons (HCs), and oxides of nitrogen (NO x ) in the exhaust emissions to an acceptable level. The reduced exhaust emissions are directed from the catalytic converter past another HO2S mounted in the rear exhaust pipe and then on into the muffler. Finally, the exhaust emissions are directed to the atmosphere through an exhaust tailpipe.

Note. On some partial zero emission vehicles (PZEV), there will be a total of 3 HO2S in the exhaust stream. One near the exhaust manifold (stream 1), one in the middle of the light-off catalyst (stream 2), and the third (stream 3) is mounted after the light-off catalyst.

Scheme 111

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Underbody Catalyst

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

Three-Way Catalytic Converter

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

Exhaust Manifold Runners

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

Exhaust Pipes

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

Heated Oxygen Sensors (HO2S)

The HO2S provide the powertrain control module (PCM) with voltage and frequency information related to the oxygen content of the exhaust gas. For information on the HO2S, refer to POWERTRAIN CONTROL MODULE (PCM) INPUTS .

Muffler

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

Supercharger Bypass (SCB) System

The SCB system allows the high pressure air at the outlet of the supercharger to vent back into the inlet of the supercharger, equalizing the pressure. This eliminates the boost (increased pressure that a supercharger produces) for times when supercharger function is undesirable. The components in this system are the vacuum bypass actuator (which controls the bypass valve inside the supercharger), an SCB solenoid, and a vacuum reservoir. The system normally operates with engine vacuum applied to the upper port of the vacuum bypass actuator, while the lower port references the air pressure in the clean air tube to cancel out any pressure difference in the intake air system. The actuator is set to open (bypassing the supercharger) during high vacuum engine conditions. As the throttle is opened and engine vacuum decreases, the actuator closes to allow the supercharger to pressurize the air in the manifold. If an undesirable condition occurs in the engine, such as overheating or a critical electronic engine control (EEC) sensor failure, the powertrain control module (PCM) also has the ability to control the SCB solenoid and direct the vacuum bypass actuator to bypass the supercharger. Once the engine condition has been corrected, the PCM allows the engine vacuum to control the vacuum bypass actuator.

Supercharger Assembly

The supercharger assembly is a positive displacement pump. Its purpose is to supply an excess volume of intake air to the engine by increasing air pressure and density in the intake manifold. The supercharger assembly incorporates the bypass system to reduce air handling losses when boost is not required, resulting in better fuel economy. When integrated on the engine, the supercharger increases torque across the entire engine operating range from 25 to 50 percent without compromising driveability or emissions. The supercharger is matched to the engine by its displacement and belt ratio, and can provide excess airflow at any engine speed. It contains 2 screw-type 3-lobed rotors. The helical shape and specialized porting provide a smooth discharge flow and a low level of noise during operation. The rotors are supported by ball bearings in front and needle bearings at the rear. The drive gears are pressed into place; therefore, the supercharger is replaced as a unit and is not repairable.

Scheme 113

Supercharger Bypass (SCB) Solenoid/(Thermactor Air Control Solenoid/Vacuum Valve Assembly)

The SCB solenoid is used to control intake manifold vacuum to the vacuum bypass actuator. This part is replaced under the part name of thermactor air control solenoid/vacuum valve assembly (part number 9H465). The PCM transmits an output signal to the SCB solenoid, thereby activating the solenoid to apply stored vacuum from the reservoir to the actuator when an undesirable condition occurs in the engine. Once the engine condition has been corrected, the solenoid will be deactivated by the PCM, allowing engine intake manifold vacuum to control the actuator. The SCB solenoid is normally de-energized.

Scheme 114

Vacuum Reservoir Assembly

The vacuum reservoir assembly stores vacuum that is applied to the vacuum actuator when a condition such as overheating or a critical sensor failure is generated. This allows the vacuum actuator to bypass the supercharger.

Scheme 115

Intercooler System

The intercooler system is designed to cool the induction air, which has been heated by the supercharger. The removal of heat from the pressurized air going into the intercooler increases the air density, which improves combustion efficiency, engine horsepower, and torque. The system consists of an additional radiator in the grille, a reservoir (independent from engine cooling system), an electric water pump, a heat exchanger (intercooler) located in the lower intake manifold, and tubing to interconnect these components.

The intercooler is positioned after the supercharger, directly in the flow of the intake air. As the heated air flows through the intercooler, heat is transferred to the coolant which is circulated back to the intercooler radiator to be cooled by the airflow through the grille. The charge air cooler pump (CAC) is controlled by the powertrain control module (PCM) to maintain a desirable intake air temperature by a second intake air temperature (IAT2) sensor in the lower intake manifold.

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The PCM-controlled charging system provides many additional benefits over the current integral generator regulator system. The first benefit is improved battery life. In an integral generator regulator system, the regulator set point is established by a temperature sensor in the regulator which estimates battery temperature. 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 will reduce 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 will momentarily lower 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's 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 will broadcast a low voltage telltale (ON) network communication message which tells the cluster to illuminate the charge indicator. The charge indicator will be illuminated if the PCM fails to see a signal on the GENLI circuit for a time period greater than 500 milliseconds. This telltale command will also be 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 will initiate a bulb check by illuminating the charge indicator. It is the PCM's responsibility to issue a low voltage telltale (OFF) command if the charging system is functioning properly. 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) network communication message is not received, the instrument cluster will continue to illuminate the charge indicator indefinitely.

Scheme 119

The Generation II (Gen II) torque based electronic throttle control (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 PCM, and an accelerator pedal assembly to control the throttle opening and engine torque. The ETC system replaces the standard cable operated accelerator pedal, idle air control (IAC) valve, 3-wire throttle position sensor (TPS), and mechanical throttle body.

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 cam 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.

It should be noted that the ETC system includes a warning indicator (wrench light) on the instrument cluster that illuminates when a fault is detected. Faults are accompanied by DTCs and may also illuminate the malfunction indicator lamp (MIL).

Electronic Throttle Body (ETB)

The Gen II ETB has the following characteristics

1. The throttle actuator control (TAC) motor is a DC motor controlled by the PCM (requires 2-wires). The gear ratio from the motor to the throttle plate shaft is 17:1.
2. There are 2 designs: parallel and in-series. 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-series design has a separate motor housing.
3. Two springs are used: one is used to close the throttle (main spring) and the other is in a plunger assembly that results in a default angle when no power is applied. This is for limp home reasons (the force of the plunger spring is 2 times stronger than the main spring). The default angle is usually set to result in a top vehicle speed of 48 km/h (30 mph). Typically this throttle angle is 7 to 8 degrees from the hard-stop angle.
4. The closed throttle plate hard stop is used to prevent the throttle from binding in the bore (~0.75 degree). This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle.
5. Unlike cable operated throttle bodies, the intent for the ETB is not to have a hole in the throttle plate or to use plate sealant. The hole is not required in the ETB because the required idle airflow is provided by the plate angle in the throttle body assembly. This plate angle controls idle, idle quality, and eliminates the need for an IAC valve.
6. The throttle position (TP) sensor has 2 signal circuits in the sensor for redundancy. The redundant throttle position signals are required for increased monitoring reasons. The first TP signal (TP1) has a negative slope (increasing angle, decreasing voltage) and the second signal (TP2) has a positive slope (increasing angle, increasing voltage). During normal operation the negative slope TP signal (TP1) is used by the control strategy as the indication of throttle position. The TP sensor assembly requires 4 circuits.

1. 5-volt reference voltage.
2. Signal return (ground).
3. TP1 voltage with negative voltage slope (5-0 volts).
4. TP2 voltage with positive voltage slope (0-5 volts).

The ETC strategy uses pedal position sensors as an input to determine the driver demand.

1. There are 3 pedal position signals required for system monitoring. APP1 has a negative slope (increasing angle, decreasing voltage) and APP2 and APP3 both have a positive slope (increasing angle, increasing voltage). During normal operation APP1 is used as the indication of pedal position by the strategy.
2. There are 2 VREF circuits, 2 signal return circuits, and 3 signal circuits (a total of 7 circuits and pins) between the PCM and the APP sensor assembly. 2 reference voltage circuits (5 volts). 2 signal return (ground) circuits. APP1 voltage with negative voltage slope (5-0 volts). APP2 voltage with positive voltage slope (0-5 volts). APP3 voltage with positive voltage slope (0-5 volts).
3. 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.
4. The 3 pedal position signals make sure the PCM receives a correct input even if 1 signal has a fault. The PCM determines if a signal is incorrect by calculating where it should be, inferred from the other signals. A value will be substituted for an incorrect signal if 2 of the 3 signals are incorrect.

Scheme 120

Electronic Throttle Control (ETC) System Strategy

The torque based ETC strategy was developed to improve fuel economy and to accommodate variable cam timing (VCT). This is possible by not coupling the throttle angle to the driver pedal position. Uncoupling the throttle angle (produce engine torque) from the pedal position (driver demand) allows the powertrain control strategy to optimize fuel control and transmission shift schedules while delivering the requested wheel torque.

The ETC monitor system is distributed across 2 processors within the PCM: the main powertrain control processor unit (CPU) and a monitoring processor called an enhanced-quizzer (E-Quizzer) processor. The primary monitoring function is carried out by the independent plausibility check (IPC) software, which resides on the main processor. It is responsible for determining the driver-demanded torque and comparing it to an estimate of the actual torque delivered. If the generated torque exceeds driver demand by a specified amount, the IPC takes appropriate corrective action.

Scheme 121

Since the IPC and main controller share the same processor, they are subject to a number of potential common failure modes. Therefore, the E-Quizzer processor was added to redundantly monitor selected PCM inputs and to act as an intelligent watchdog and monitor the performance of the IPC and the main processor. If it determines that the IPC function is impaired in any way, it takes appropriate Failure Mode and Effects Management (FMEM) actions.

ETC SYSTEM FAILURE MODE AND EFFECTS MANAGEMENT

ELECTRONIC THROTTLE MONITOR OPERATION

Accelerator and Throttle Position (TP) Sensor Inputs

ACCELERATOR PEDAL POSITION (APP) SENSOR CHECK

THROTTLE POSITION (TP) SENSOR CHECK

Throttle Plate Position Controller (TPPC) Outputs

The purpose of the TPPC is to maintain the throttle position at the desired throttle angle. It is a separate chip embedded in the PCM. The desired angle is communicated from the main CPU via a 312.5 Hz duty cycle (DC) signal. The TPPC interprets the duty cycle signal as follows

1. Less than 5% - Out of range, limp home default position.
2. Greater than or equal to 5% but less than 6% - Commanded default position, closed.
3. Greater than or equal to 6% but less than 7% - Commanded default position. Used for key-on, engine off.
4. Greater than or equal to 7% but less than 10% - Closed against hard-stop. Used to learn zero throttle angle position (hard-stop) after key-up.
5. Greater than or equal to 10% but less than or equal to 92% - Normal operation, between 0 degrees (hard-stop) and 82 degrees, 10% duty cycle equals 0 degrees throttle angle, 92% duty cycle equals 82 degrees throttle angle.
6. Greater than 92% but less than or equal to 96% - Wide Open Throttle, 82 to 86 degrees throttle angle.
7. Greater than 96% but less than or equal to 100% - Out of Range, limp home default position.

The desired angle is relative to the hard-stop angle. The hard-stop angle is learned during each key-up process before the main CPU requests the throttle plate be closed against the hard-stop. The output of the TPPC is a voltage request to the H-driver (also in PCM). The H driver is capable of positive or negative voltage to the electronic throttle body motor.

THROTTLE PLATE CONTROLLER CHECK OPERATION

The dual-injection fuel delivery system consists of a fuel select switch circuit, the fuel rails, the fuel injectors, and a fuel injector control module (FICM).

The FICM controls the fuel injectors according to the demand from the powertrain control module (PCM). The FICM enables the primary (forward) fuel injectors when in single-injection mode and enables both the primary (forward) and secondary (rearward) fuel injectors when in dual-injection mode. The injection mode is requested by the PCM through the fuel select switch circuit. The FICM communicates the fuel injection mode status to the PCM on the SCP network.

Fuel Select Switch Circuit

The fuel select switch (FSSW) circuit is used by the PCM to toggle between single-injection and dual-injection fuel modes. When torque demand reaches a calibrated limit the PCM requests the secondary injectors by toggling the FSSW circuit.

Fuel Rails

The fuel rails route fuel to the fuel injectors.

Scheme 122

The dual-injection fuel delivery system uses 2 injectors per cylinder paired together. The primary injectors are slightly forward of the secondary injectors.

Scheme 123

Fuel Injector Control Module (FICM)

The FICM receives input from the PCM. Based on the information received and programmed into its memory, the FICM generates output signals to control the injector solenoids. The FICM contains a set of drivers for both the primary (forward) and secondary (rearward) fuel injectors. Fuel injector driver signals from the powertrain control module (PCM) are used to control both sets of output drivers in the FICM. Based on the fuel selector switch input, the FICM controls either the primary or both the primary and secondary fuel injectors.

See also:
• SYMPTOM CHARTS - GASOLINE MODELS
• DIAGNOSTIC METHODS - GASOLINE MODELS
• POWERTRAIN DTC CHARTS AND DESCRIPTIONS - GASOLINE MODELS
• ENGINE FAMILY GROUP WORK SHEET
• HEATED OXYGEN SENSOR (HO2S) MONITOR
• GENERIC MISFIRE PROCESSING
• POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM MONITOR
• VARIABLE CAM TIMING (VCT) SYSTEM
• POWERTRAIN CONTROL MODULE (PCM) INPUTS
• POWERTRAIN CONTROL MODULE (PCM) OUTPUTS
• WIDE OPEN THROTTLE A/C CUT-OFF (WAC)
• FAIL-SAFE COOLING STRATEGY
• DIFFERENTIAL PRESSURE FEEDBACK EGR (DPFE) SYSTEM
• FUEL PUMP DRIVER MODULE (FPDM)
• FAN CONTROL
• TRANSMISSION CONTROL SWITCH (TCS)
• AIR CONDITIONING CLUTCH RELAY (A/CCR)
• THROTTLE POSITION (TP) SENSOR
• CATALYST EFFICIENCY MONITOR