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GM Scan
Tool OBD II
General
Motors
Scan Tool Interface
Single Interface Accesses Both
Manufacturer-Specific and
Generic OBD II Functions
Initial Display
F0: Diagnostics - Contains
various submenus used to
perform diagnostic functions
(look at DTCs, Freeze
Frame, etc.)
F1: Service Programming Reflashing PCM
F2: View Captured Data - Allows
you to view any Captured
Snapshot Information
Main Menu
F0: Diagnostic Trouble Codes
(View DTCs)
F1: Data Display (View the data
display for Engine/Transmission)
F2: Special Functions (takes
you to Output Controls)
F3: Snapshot (allows you to take
a snapshot movie of data)
parameters around a trigger)
F4: System Information
(Readiness Status of Monitors)
F5: ID Information (displays
calibration ID and VIN)
Selecting Engine or
Transmission Data
Data parameters are grouped
by Engine (F0) and Transmission
(F1).
Data displays for the
engine and transmission
are presented in two separate
groups
Select the F0 or F1 keys to select
Engine or Transmission
DTC Information
F0: DTC Information lets
you look at all stored DTCs
F1: Specific DTC lets you view
an individual DTC by entering
its number
F2: Freeze Frame/Failure Records
takes you to a list of all stored
Freeze Frame and Failure Records
F3: Clear DTC Information lets
you erase DTCs and FF/FR
F4: Diagnostic Test Status takes
you to a list that shows the
current status of tests that stored
Freeze Frame or Fail Records
F0: DTC Information
In addition to allowing you to
look at any History Codes,
this menu lets you determine
WHEN the test failed.
Use this menu to help you
determine if:
 the DTC set since DTCs were
cleared,
 the test has run and failed
 it has run and failed this ignition
DTC Display
If a Specific DTC is
selected, a display shows
its number, a brief
description of the DTC,
and the test status
Use the test status
information to tell you
if the test has run, and
whether or not the test
passed or failed
Freeze Frame/
Failure Records
This Application Menu
display is an important
one since it contains so
many diagnostic
options related to
system faults (DTCs,
FF, FR, etc.)
For example, we
can select:
F2: Freeze Frame/
Failure Records
Freeze Frame (FF)
Failure Records (FR)
The Freeze Frame/
Failure Records
window shows the
Freeze Frame for a
DTC that turned on
the MIL, and a list
of all Fail Records
Cursor down to select the
data to view and hit Enter, or
select the function key
corresponding to the FF or FR
you want to view (F0, F1, etc.)
Freeze Frame
Data
This is the
mandated Freeze
Frame data
required by
OBD II
regulations
Note that fuel
trim is displayed in
both percent and in
the traditional GM
Fuel Trim Counts
Failure
Records
Failure Record data
looks like Freeze Frame.
It is a diagnostic
enhancement that
stores data for as many
as many as five separate
faults
Failure Records are
the most current
diagnostic information
and, unlike Freeze
Frame, can be
updated by the PCM
Clearing DTCs
Choose Clear DTC
Information to erase
all DTCs from memory
This will erase all DTCs
and Freeze Frame, and
on 1997 and later
GM vehicles it will reset
all Readiness Flags
1995-96 GM vehicles reset
only the monitor(s)
related to the DTC(s)
Clear DTC Information
You’ll be prompted with
a Yes/No choice before
DTCs are erased
DO NOT erase
DTCs
unless you have saved
Freeze Frame data,
or you’ll lose it.
Freeze Frame (FF)
is cleared with the DTC
information
Selecting
Diagnostic Test Status
To view the current status
of a fault-related test,
use the Up/Down Arrow Keys
to highlight the selection
and hit Enter,
or push the F4 key
This will take you to the
Diagnostic Test Status Display
Diagnostic Test Status
The Diagnostic Test
Status display lists all FF
and FR and their test status
Yes/No in the RAN column
tells you if the test ran
Yes/No in the FAIL column
indicates Pass/Fail status
INT suggests the possibility
of an intermittent
Use this information before,
during, and after repairs to
evaluate system status
Data Display
Data Parameters are
grouped into four
main categories
Engine data parameters
are broken into two groups
(Engine Data 1 and 2)
on vehicles with a large
parameter list and some
parameters may appear
on both lists
Use the groups to
concentrate on areas of
concern (e.g. EGR
concerns versus misfire)
Data Parameters
Use the white boxes at the
bottom of the display to:
Select Items from the
data display list for
viewing and recording
Go directly to DTCs
Capture Data using
the snapshot feature
The More choice sends
you to other menu
options
Special
Functions
Want to get to
those bidirectional
controls?
The ones we call
Output Tests?
Select
Special Functions
from this menu
Output Controls
There are several submenu
options that allow you to
go to subsystems
and activate various
components
To select
Engine Output Controls,
hit F0 or hit the Enter key
with F0 highlighted as
shown
Engine Output
Controls Menu
This display shows a number
of components that you
can activate through the
scan tool to test their
performance
You can use this menu to test
the bulb in the MIL, operate
the fuel pump and cooling
fans, etc.
Output Test Fan Relay
The ON/OFF
boxes at the bottom
of the screen are
used to command
the component
In addition,
parameters of your
choice (Select Items)
can be viewed
during the test
EVAP
Purge Solenoid
Other types of output
controls enable you
to activate a pulse width
modulated component
like the EVAP Purge
Solenoid and look at
the system response
Here, we’re watching fuel
tank pressure and fuel trim as
we gradually open the purge
using the Decrease and
Increase control buttons
Fuel and IAC
Controls
You can also concentrate
on the Fuel or IAC Systems
Fuel system controls allow
injector balance tests and
IAC control
Separate menu choices
let you reset adaptive fuel
trim and IAC learned values
during or after a repair
without having to disconnect
the battery
Summary
GM supports all Generic OBD II functions
Individual data parameters can be viewed
These parameters are located in groups
(Engine 1, Engine 2, etc.)
Various output tests are available, including
tests of individual components
In addition to Freeze Frame, the PCM
provides GM-specific enhancements:
Failure Records, DTC Information,
and Diagnostic Test Status display