Ford F150 Pickup. Manual — part 1404

FAILURE MODE EFFECTS MANAGEMENT

FMEM mode allows system operation when sensors fail or transmit signals that are out of normal operating
range. During FMEM mode, PCM substitutes a mid-range signal for defective sensor while continuing to
monitor sensor. If faulty sensor signals return to normal operating range, PCM will use those signals.
Depending on specific failure, a fault code may be set in PCM memory.

HARDWARE LIMITED OPERATIONAL STRATEGY

If a number of system or sensor failures are present and PCM is not receiving enough information to operate,
PCM will switch to HLOS mode. PCM will output fixed values to allow operation of vehicle. Driveability
concerns will be present. PCM will not output diagnostic trouble codes in this mode.

ENGINE RPM/VEHICLE SPEED LIMITER

The Powertrain Control Module (PCM) will disable some or all fuel injectors whenever an engine RPM or
vehicle overspeed condition is detected. The purpose of engine RPM/vehicle speed limiter is to prevent damage
to vehicle powertrain. Vehicle will run rough, and PCM will store a continuous memory DTC P1270. When
overspeed condition is over, engine will return to normal operation. If necessary, clear DTC P1270 from PCM.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

DIAGNOSTIC MONITORS

DESCRIPTION

Starting with 1996 model year, all California passenger cars and trucks (up to 14,000 GVW) and all federal
passenger cars and trucks (up to 8500 GVW) are required to comply with either CARB OBD-II or EPA OBD
requirements. Federal heavy-duty truck up to 10,000 lbs. GVWR choosing to certify using Light Duty Truck
provisions must comply with OBD-II requirements. Federal heavy-duty trucks over 8500 GVW are not required
to comply with any OBD regulation, however in order to meet minimum serviceability requirements, must
comply with OBD-I requirements. OBD-II requirements apply to gasoline vehicles, diesel vehicles, ethanol
flexible fuel vehicles and bi-fuel CNG/LPG vehicles while running on gasoline. OBD-II requirements are being
phased in on dedicated CNG and bi-fuel CNG/LPG vehicles while running on gaseous fuels. Passenger cars and
trucks sold in Canada and Mexico have Federal calibrations, unless unique calibrations are certified for Mexico
at high altitude.

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 50-100 k/mile emission standards. If a system or component exceeds emission thresholds or fails to
operate within a manufacturer's specifications, a DTC will be stored and MIL will be illuminated within 2
driving cycles. OBD-II system monitors for malfunctions either continuously, regardless of driving mode, or
non-continuous, once per drive cycle during specific drive modes. A pending DTC is stored in PCM Keep Alive
Memory (KAM) when a malfunction is initially detected. This pending DTC may be erased on the third vehicle
restart after 2 consecutive drive cycles with no malfunction. However, if malfunction is still present after 2
consecutive drive cycles, MIL is illuminated. Once MIL is illuminated, 3 consecutive drive cycles without a
malfunction detected are required to extinguish MIL. DTC is erased after 40 engine warm-up cycles once MIL
is extinguished.

In addition to specifying and standardizing much of the diagnostics and MIL operation, OBD-II requires the use
of a standard Diagnostic Link Connector (DLC), standard communication links and messages, standardized
DTCs and terminology. Examples of standard diagnostic information are freeze frame data and Inspection
Maintenance (IM) readiness indicators. Freeze frame data describes data stored in KAM at the point the
malfunction is initially detected. 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 will be replaced if a fuel or misfire fault is detected. This data is
accessible with scan tool to assist in repairing vehicle. OBD IM readiness indicators show whether all of the
OBD monitors have been completed since last time KAM or PCM DTC(s) have been cleared. A DTC P1000 is
also stored to indicate that some monitors have not completed. In some states, it may be necessary to perform an
OBD check in order to renew a vehicle registration. The IM readiness indicators must show that all monitors
have been completed prior to OBD check. DIAGNOSTIC MONITORING TESTS provides a general
description of each OBD-II monitor. In these descriptions, monitor strategy, hardware, testing requirements and
methods are presented to provide an overall understanding of monitor operation.

CATALYST EFFICIENCY MONITOR

Description

Catalyst Efficiency Monitor uses an oxygen sensor before and after catalyst to infer hydrocarbon efficiency

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

based on oxygen storage capacity of catalyst. Under normal, closed-loop fuel conditions, high efficiency
catalysts have significant oxygen storage. This makes switching frequency of rear Heated Oxygen Sensor
(HO2S) very slow and reduces amplitude of those switches as compared to switching frequency and amplitude
of front HO2S. As catalyst efficiency deteriorates due to thermal and/or chemical deterioration, its ability to
store oxygen declines. Post-catalyst or downstream HO2S signal begins to switch more rapidly with increasing
amplitude, approaching switching frequency and amplitude of pre-catalyst or upstream HO2S.

All vehicles utilize a Federal Test Procedure (FTP) based catalyst monitor. Meaning catalyst monitor must run
during a standard FTP emission test. This differs from a 20 second steady state catalyst monitor used in 1994-96
vehicles. Currently, 2 slightly different versions of catalyst monitor are utilized; Switch Ratio Method and Index
Ratio Method. Beginning with 2001 model year, both versions will continue to be used in subsequent model
years.

Switch Ratio Method (1996-Later)

In order to assess catalyst oxygen storage, monitor counts front and rear HO2S switches during part-throttle,
closed-loop fuel condition after engine is warmed-up and 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 required number of front switches has
accumulated in each cell, the total number of rear switches is divided by total number of front switches to
compute a switch ratio. A switch ratio near zero indicates high oxygen storage capacity. Therefore, high HC
efficiency. A switch ratio near one, indicates low oxygen storage capacity. Therefore, low HC efficiency. If
actual switch ratio exceeds a calibrated threshold switch ratio, the catalyst is considered faulty. Inputs from ECT
or CHT (warm engine), IAT (not extreme ambient temperatures), MAF (greater than minimum engine load),
VSS (within vehicle speed window) and TP (at part-throttle) are required to enable Catalyst Efficiency Monitor.

The following are typical switch ratio monitor entry conditions:

z

Part throttle with no rapid throttle transients.

z

Minimum 330 seconds since start-up at 70°F (21°C).

z

ECT or CHT is 170-230°F (76.6-110°C).

z

IAT is 20-180°F (-6°C to 82°C)

z

Engine load more than 10 percent.

z

Time since entering close loop is 30 seconds.

z

Vehicle speed is 5-70 MPH.

z

Inferred Catalyst Mid-bed Temperature is 900°F (482°C).

z

Mass air flow is 1-5 lbs./minute.

z

Fuel level more than 15 percent.

z

EGR is 1-12 percent.

NOTE:

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

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

DTCs associated with this test are DTC P0420 (Bank No. 1 or Y-pipe system), and P0430 (Bank No. 2).
Because an exponentially weighted moving average algorithm is used for malfunction determination, up to 6
driving cycles may be required to illuminate MIL during normal customer driving. If KAM is reset or battery is
disconnected, a malfunction will illuminate MIL in 2 drive cycles.

Index Ratio Method (Some 2001-Later)

In order to assess catalyst oxygen storage, catalyst monitor counts front HO2S switches during part-throttle,
closed-loop fuel conditions after engine is warmed-up and 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, front and rear HO2S signal lengths are continually being calculated. When required
number of front switches has accumulated in each cell, total signal length of rear HO2S is divided by total
signal length of front HO2S to compute a catalyst index ratio. An index ratio near zero, indicates high oxygen
storage capacity. Therefore, high efficiency. A switch ratio near one, indicates low oxygen storage capacity.
Therefore, low HC efficiency. If actual index ratio exceeds threshold index ratio, catalyst is considered faulty.
Inputs from ECT or CHT (warm engine), IAT (not extreme ambient temperatures), MAF (greater than
minimum engine load), VSS (within vehicle speed window) and TP (at part-throttle) are required to enable
Catalyst Efficiency Monitor.

The following are typical switch ratio monitor entry conditions:

z

Minimum 330 seconds since start-up at 70°F (21°C).

z

ECT or CHT is 170-230°F (76.6-110°C).

z

IAT is 20-180°F (-6 to 82°C).

z

Time since entering close loop is 30 seconds.

z

Inferred Rear HO2S sensor temperature of 900°F (482°C).

z

EGR is 1-12 percent.

z

Part throttle, maximum rate of change 0.2 volt/0.050 second.

z

Vehicle speed is 5-70 MPH.

z

Fuel level more than 15 percent.

z

First Air Flow Cell

A. Engine RPM, 1000-1300 RPM.

B. Engine load 15-35 percent.

C. Inferred catalyst temperature is 850-1200°F (454-649°C).

D. Number of front O2 switches is 50.

z

Second Air Flow Cell

A. Engine RPM, 1200-1500 RPM.

B. Engine load 20-35 percent.

C. Inferred catalyst temperature is 900-1250°F (482-677°C).

D. Number of front O2 switches is 70.

z

Third Air Flow Cell

A. Engine RPM, 1300-1600 RPM.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline