Eobd Readiness Monitors; Eobd Monitor Readiness Status; Eobd Definitions; Eobd Modes Of Operation - Sealey VS8812 Instructions Manual

be operated under specific conditions before the monitor is ready. These monitors are termed non-continuous monitors and are listed
below:
1) eGr System
2) o2 Sensors
3) catalyst
4) evaporative System
5) o2 Sensor Heater
6) Secondary air
7) Heated catalyst
8) A/c system
3.5.

EOBD Monitor Readiness Status

eoBd systems must indicate whether or not the vehicle's Pcm's monitor system has completed testing on each component.
components that have been tested will be reported as "ready", or "complete", meaning they have been tested by the eoBd system.
the purpose of recording readiness status is to allow inspectors to determine if the vehicle's eoBd system has tested all the
components and/or systems.
the power train control module (Pcm) sets a monitor to "ready" or "complete" after an appropriate drive cycle has been performed.
the drive cycle that enables a monitor and sets readiness codes to "ready" varies for each individual monitor. once a monitor is set
as "ready" or "complete", it will remain in this state. A number of factors, including erasing of diagnostic trouble codes (dtcs) with
a scan tool or a disconnected battery, can result in readiness monitors being set to "not ready". Since the three continuous monitors
are constantly evaluating, they will be reported as "ready" all of the time. If testing of a particular supported non-continuous monitor
has not been completed, the monitor status will be reported as "not complete" or "not ready".
In order for the eoBd monitor system to become ready, the vehicle should be driven under normal operating conditions. these
operating conditions may include a mix of highway driving and stop and go, city type driving, and at least one overnight-off period. for
specific information on getting your vehicle's EOBD monitor system ready, please consult your vehicle owner's manual.
3.6.

EOBD Definitions

Powertrain control module (Pcm) - eoBd terminology for the on-board computer that controls engine and drive train. malfunction
Indicator Light (mIL) - malfunction Indicator Light (check engine) is a term used for the light on the instrument panel. It is to
alert the driver and/or the repair technician that there is a problem with one or more of vehicle's systems and may cause emissions
to exceed standards. If the mIL illuminates with a steady light, it indicates that a problem has been detected and the vehicle
should be repaired as soon as possible. Under certain conditions, the dashboard light will blink or flash. This indicates a severe
problem and flashing is intended to discourage vehicle operation. The vehicle on board diagnostic system can not turn the MIL off until
necessary repairs are completed or the condition no longer exists.
dtc - diagnostic trouble codes (dtc) that identify which section of the emission control system has malfunctioned.
Enabling Criteria - Also termed Enabling Conditions. They are the vehicle-specific events or conditions that must occur within the
engine before the various monitors will set, or run. Some monitors require the vehicle to follow a prescribed "drive cycle" routine as
part of the enabling criteria. drive cycles vary among vehicles and for each monitor in any particular vehicle.
EOBD Drive Cycle - A specific mode of vehicle operation that provides conditions required to set all the readiness monitors applicable
to the vehicle to the "ready" condition. the purpose of completing an eoBd drive cycle is to force the vehicle to run its onboard
diagnostics. Some form of a drive cycle needs to be performed after dtcs have been erased from the Pcm's memory or after the
battery has been disconnected. running through a vehicle's complete drive cycle will set the readiness monitors so that future faults
can be detected. drive cycles vary depending on the vehicle and the monitor that needs to be reset. For vehicle specific drive cycle,
consult the vehicle's owner's manual.
freeze frame data - When an emissions related fault occurs, the eoBd system not only sets a code but also records a snapshot
of the vehicle operating parameters to help in identifying the problem. this set of values is referred to as freeze frame data and may
include important engine parameters such as engine RPM, vehicle speed, air flow, engine load, fuel pressure, fuel trim value, engine
coolant temperature, ignition timing advance, or closed loop status.
3.7.

EOBD Modes of Operation

Introduction to the eoBd communication protocol.
Mode $01 - Identifies the Powertrain information and shows current data available to the scan tool. This data includes: DTCs set, status of
on-board tests and vehicle data such as engine RPM, temperatures, ignition advance, speed, air flow rates, and closed loop status for
fuel system.
mode $02 - displays freeze frame data. Same data as in mode 1, but it was captured and stored when a malfunction occurred and a
dtc was set. Some of the PIds for mode one are not implemented in this mode.
mode $03 - displays the type of powertrain or emission related dtcs stored by a 5 digit code identifying the faults. there may be more
than one response message if there are more trouble codes than will fit in the data bytes of the response message, or if there are more
than one Pcm computer responding.
mode $04 - used to clear dtcs and freeze frame data. this clears all diagnostic trouble codes that may be set including freeze frame
data and readiness monitors.
mode $05 - oxygen Sensor test results. this mode displays the oxygen sensor monitor screen and the test results gathered about the
oxygen sensor.
there are ten numbers available for diagnostics:
1. $01 rich-to-Lean o2 sensor threshold voltage
2. $02 Lean-to-rich o2 sensor threshold voltage
3. $03 Low sensor voltage threshold for switch time measurement
4. $04 High sensor voltage threshold for switch time measurement
5. $05 rich-to-Lean switch time in ms
6. $06 Lean-to rich switch time in ms
7. $07 minimum voltage for test
8. $08 maximum voltage for test
9. $09 time between voltage transitions in ms
mode $06 - non-continuously monitored Systems test results. there are typically a minimum value, a maximum value, and a current
value for each non-continuous monitor. This data is optional, and it is defined by a given vehicle make if it's used.
mode $07 - request for dtcs (pending) from continuously monitored Systems after a single driving cycle has been performed to
© Jack Sealey Limited
Original Language Version
Page 3
VS8812 | Issue 1 27/02/17