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Table of Contents

Introduction OBD-I and OBD-II....................................................................... 3

Catalyst Efficiency Monitor................................................................................. 4

Misfire Monitor..................................................................................................... 7

Electric AIR System Monitor ............................................................................ 11

Mechanical AIR System Monitor ..................................................................... 12

EVAP System Functional Monitor Purge Valve Functional Check............ 13

EVAP System Monitor - 0.040 dia. Leak Check ........................................... 15

Fuel System Monitor ........................................................................................ 18

HO2S Monitor ................................................................................................... 19

DPFE EGR System Monitor ............................................................................ 23

Sonic EGR System Monitor............................................................................. 28

Comprehensive Component Monitor - Engine............................................... 30

Comprehensive Component Monitor - Transmission .................................... 35

4R70W (RWD) Transmission .......................................................................... 41
FORD MOTOR COMPANY
REVISION DATE: JULY 30, 2001
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AX4S (FWD) Transmission.............................................................................. 42

CD4E (FWD) Transmission ............................................................................. 43

4R44E (A4LD) (RWD) Transmission .............................................................. 44

4R100 (E4OD) (RWD) Transmission.............................................................. 45

On Board Diagnostic Executive....................................................................... 46

Exponentially Weighted Moving Average ....................................................... 47

I/M Readiness Code......................................................................................... 49

Serial Data Link MIL Illumination ..................................................................... 49


FORD MOTOR COMPANY
REVISION DATE: JULY 30, 2001
PAGE 3 OF 49

Introduction OBD-I and OBD-II
OBD-II Systems
California OBD-II applies to all gasoline engine vehicles up to 14,000 lbs. Gross Vehicle Weight Rating (GVWR)
starting in the 1996 MY and all diesel engine vehicles up to 14,000 lbs. GVWR starting in the 1997 MY.

Federal OBD applies to all gasoline engine vehicles up to 8,500 lbs. GVWR starting in the 1996 MY and all diesel
engine vehicles up to 8,500 lbs. GVWR starting in the 1997 MY.

OBD-II system implementation and operation is described in the remainder of this document.

OBD-I Systems
If a vehicle is not required to comply with OBD-II requirements, it utilizes an OBD-I system. OBD-I systems are
used on all over 8,500 lbs. GVWR Federal truck calibrations. With the exception of the 1996 MY carryover EEC-IV
OBD-I systems, Federal > 8,500 lbs. OBD-I vehicles use that same PCM, J1850 serial data communication link,
J1962 Data Link Connector, and PCM software as the corresponding OBD-II vehicle. The only difference is the
possible removal of the rear oxygen sensor(s), fuel tank pressure sensor, canister vent solenoid, and a different
PCM calibration.

The following list indicate what monitors and functions have been altered for OBD-I calibrations:

Monitor / Feature
Calibration
Catalyst Monitor
Not required, monitor calibrated out, rear O2 sensors may be deleted.
Misfire Monitor
Calibrated in for service, all DTCs are non-MIL. Catalyst damage misfire criteria
calibrated out, emission threshold criteria set to 4%, enabled between 150
o
F and 220
o
F, 254 sec start-up delay.
Oxygen Sensor Monitor Rear O2 sensor test calibrated out, rear O2 sensors may be deleted, front O2 sensor
response test calibrated out, O2 heater current test calibrated out prior to 2002 MY, O2
heater voltage test used for all model years.
EGR Monitor
Same as OBD-II calibration except that P0402 test uses slightly higher threshold.
Fuel System Monitor
Same as OBD-II calibration starting in 2002 MY, earlier calibrations used +/- 40%
thresholds.
Secondary Air Monitor
Functional (low flow) test calibrated out, circuit codes are same as OBD-II calibration.
Evap System Monitor
Evap system leak check calibrated out, fuel level input circuit checks retained as non-
MIL. Fuel tank pressure sensor and canister vent solenoid may be deleted.
Comprehensive
Component Monitor
All circuit checks same as OBD-II. Some rationality and functional tests calibrated out.
(MAF/TP rationality, IAC functional)
Communication
Protocol and DLC
Same as OBD-II, all generic and enhanced scan tool modes work the same as OBD-II
but reflect the OBD-I calibration that contains fewer supported monitors. "OBD
Supported" PID indicates OBD-I.
MIL Control
Same as OBD-II, it takes 2 driving cycles to illuminate the MIL.
FORD MOTOR COMPANY
REVISION DATE: JULY 30, 2001
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Catalyst Efficiency Monitor
The Catalyst Efficiency Monitor uses an oxygen sensor before and after the catalyst to infer the hydrocarbon
efficiency based on oxygen storage capacity of the ceria and precious metals in the washcoat. Under normal,
closed-loop fuel conditions, high efficiency catalysts have significant oxygen storage. This makes the switching
frequency of the rear HO2S very slow and reduces the amplitude of those switches as compared to the switching
frequency and amplitude of the front HO2S. As catalyst efficiency deteriorates due to thermal and/or chemical
deterioration, its ability to store oxygen declines. The post-catalyst HO2S signal begins to switch more rapidly with
increasing amplitude, approaching the switching frequency and amplitude of the pre-catalyst HO2S. The
predominant failure mode for high mileage catalysts is chemical deterioration (phosphorus deposition on the front
brick of the catalyst), not thermal deterioration.
Steady State Method
The steady-state catalyst monitor performs a 20 second test during steady state rpm and load conditions at higher
vehicle speeds. The monitor is an active/intrusive monitor. During the test, closed loop fuel control is temporarily
transferred from the pre-catalyst, fuel control oxygen sensors to post-catalyst oxygen sensors under specific,
steady state conditions. If the catalyst has sufficient oxygen storage, the closed loop cycling frequency will be much
longer than the cycling frequency observed during normal fuel control. As oxygen storage degrades, the closed
loop frequency from the post-catalyst sensors become short. At the end of the 20-second test period, the PCM
calculates a closed loop switching frequency based on the rpm/load conditions at the time of the test. If the
measured frequency is higher than the catalyst efficiency malfunction threshold frequency, a malfunction is
indicated. Threshold frequencies (Hz) are stored in a calibration table as a function of rpm/load.
Switch Ratio Method
Most vehicle applications utilize an FTP-based (Federal Test Procedure) catalyst monitor. This simply means that
the catalyst monitor must run during a standard FTP emission test as opposed to the 20-second steady-state
catalyst monitor used on 1994 through some 1996 vehicles.
In order to assess catalyst oxygen storage, the monitor counts front and rear HO2S switches during part-throttle,
closed-loop fuel conditions after the engine is warmed-up and inferred catalyst temperature is within limits. Front
switches are accumulated in up to nine different air mass regions or cells although 5 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 (air mass region), 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 the threshold switch ratio, the catalyst is considered failed.
General Catalyst Monitor Operation
Rear HO2S sensors can be located in various ways to monitor different kinds of exhaust systems. In-line engines
and many V-engines are monitored by individual bank. A rear HO2S sensor is used along with the front, fuel-
control HO2S sensor for each bank. Two sensors are used on an in-line engine; four 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 one rear HO2S sensor along with the two front, fuel-control HO2S
sensors. Y-pipe system uses three sensors in all. For Y-pipe systems, the two front HO2S sensor signals are
combined by the 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.
Most vehicles that are part of the LEV catalyst monitor phase-in will monitor less than 100% of the catalyst
volume often the first catalyst brick of the catalyst system. Partial volume monitoring is done on LEV and ULEV
vehicles in order to mee