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					       S    o have you
            been through
a good OBD II training
                            however explain what
                            this stuff is all about.
                                                        results for continuous
                                                        monitored systems,
                                                        Mode 8- Request control
class lately? If you are            I can think of no   of onboard systems (bi-
like most, you have         better way of               directional) and Mode 9-
probably just about over    understanding mode six      Module identification.
dosed on them! There is     than to first discuss the
one thing that you may      various 9 modes of OBD
have been referenced        II.
too while attending one
of these classes                    SAE (Society of
however, Mode Six.          Automotive Engineers)
                            document J1979 stated
        What is mode        that there would be 9
six? Better than that,      modes of operation for
why would we want to        ALL OBD II vehicles
use mode six and even       that both the EPA
better yet, where can I     (Environmental
get the mode six            Protection Agency) and
hexadecimal code            the CARB (California
abbreviations? You see,     Air Resources Board)
many people refer to        have adopted.
mode six, than they just
cut you loose without               Those 9 modes
ever giving you that        of operation are as
information. This is        follows; Mode 1-
kind of like being          request current power
dropped off in a foreign    train data (DataStream),
country without having      Mode 2- request freeze              We should state
an understanding of         frame data, Mode 3-         that these regulations
their language. You feel    Request diagnostic          pertain to
angry and helpless.         trouble codes, Mode 4-      Global/Generic OBD II!
Refer to the sample         Clear/reset DTCs, freeze    This is very important to
graphic in the right hand   frame data, and             remember since some
column of this page to      readiness status            vehicles will not be able
see a typical Mode six      monitors for non-           to display Mode six data
scan tool screen.           continuous monitors         on the factory or OEM
                            only, Mode 5- request       side of their OBD II
        The later part of   oxygen sensor monitor       computer systems.
this manual will give the   test results, Mode 6-
mode six information as     Request onboard                      There may be a
well as trouble code        monitoring test results     little confusion when
diagnostics for Ford,       for non-continuous          trying to view these
GM, and Chrysler            monitored systems,          various modes of
products. We must first     Mode 7- Request             operation while using
                            onboard monitoring test     your scan tool. The
modes are generally not      are any emissions            over 90% of all vehicles
listed by their hex code     related trouble codes        can be successfully
listings. They are           stored. If there are than    repaired using just the
usually listed by a short    it will fail. The            generic side of OBD II.
phrase such as data          inspector will also be       In fact, it makes perfect
stream, trouble codes,       sure that the monitors       sense to use generic side
other results, etc. Also     have been tested and         since that is what the
it is important to note      completed. This is           emissions programs are
that not ALL scan tools      where some states start      using!
can do all nine modes of     to vary. Typically the
operation! Be sure to        states will allow up to
check with the               two monitors not to have
manufacture before           been completed yet. We
purchasing that new          should note that if there
scan tool. Surprisingly      was originally a code
enough the cheaper           stored, than a repair
tools will do all nine       performed, that this
modes.                       monitor would have to
                             have been completed
        Why is it so         before passing the
important for us to          emissions test.
master these various?
Modes of operation?                  We strongly
Quite simply, this is        recommend you
what MOST state              checking your current                Alright, now that
emissions programs           State’s emissions            we have discussed some
follow. The typical state    program to become            general housekeeping
emissions program            familiar with its            concerning mode six, it
usually goes something       workings. One example        is time for us to discuss
like this.                   of using these modes to      what mode six is and
                             their fullest potential      more importantly, what
                             would be to use mode 4       can it do for you?
                             to reset just the monitor
                             you need to, instead of              Mode six is
                             resetting all the            basically three-part
                             monitors! Remember,          processes that a
                             factory scan tools are       technician can use to not
        The consumer         great, however they may      only repair a vehicle, but
will take their vehicle      not allow all the features   to drastically cut down
for an enhanced OBD II       needed to test/repair        the amount of time it
emissions test. The          these emissions failures.    takes to do so! So you
inspector will find the      This is just one example     may be asking yourself,
diagnostic connector and     of such a case.              why haven’t I heard of
attach their generic scan                                 this before or if I did,
tool software to it. They           I will go on the      why isn’t everybody
will check to see if there   record as saying that        using it?
Well if you have ever                 Right about this     assuming we know what
pulled up a mode six          time you may be asking       we are looking at.
screen than you already       yourself “What is all this   Using the back pages of
know the answer to this       talk about hexadecimal       this manual we see that
question.                     coding and how will it       the TID $41refers to the
                              help me fix a vehicle?”      EGR system and the
         Mode six is          Lets take a look at a        CID $12 refers
displayed in something        sample mode six case         specifically to the
called hexadecimal            study in action.             problem affecting the
code. The prefix hex                                       downstream DPFE hose.
may lead you to believe               Below we have a      The test spec lists a
the number 6 is               screen shot of an EASE       pressure measurement
involved, in all actuality    diagnostic software scan     (in H2O). In other
the hexadecimal system        tool loaded on a laptop.     words we have a
as it applies to cars is a    We are viewing a mode        pressure problem.
16 digit system. The          six screen that is telling
numbers 0-9 make up           us everything we want
the first 10 digits and the   to know to repair this
Capital letters A-F           car quickly.
comprise the last 6
                                                           0 1 2 3 4 5 6 7 8 910 11 12 13 14 15
digits. The hex system
is used by most of the
world in the math,
                                                           0123456789A B C D E F
science and computer
                                                                Hexadecimal Coding
industries, however the
American numbering
system is in decimals.
The American system is                                              Let us go back to
also 16 places labeled 0-                                  something we said
15. Refer to the chart in              Our case vehicle    earlier, “mode six is a
the right hand column of      is a 1999 Ford Explorer      three step process”.
the page as an example.       with a 4.0-liter engine.     Step 1 of mode six
                              We see that we are           allows us to see if a
        There is a            failing the mode six         monitor is going to fail a
complex mathematical          screen for TID (Test         test or if it has already
equation that one can         Identification) number       failed a test. This is a
use to convert                $41 and CID                  lot like pending codes or
hexadecimal coding into       (Component                   the General Motors
something that we can         Identification) number       version called failure
understand, however we        $12. It even gives us        records. This in itself is
have included the             normal operating values      a great time saver!
hexadecimal code              and pass/fail cut points.    Imagine not having to
meanings for the various      Hey this is all done         drive those long drive
domestic car lines for        without even leaving the     cycles anymore to see if
you throughout the rest       driver’s seat! Pretty        a monitor is going to fail
of this manual.               cool huh? Well, that is      a test. This feature
allows us to see if the               I think you will      In other words, this is
PCM has run the first of      agree that this is            the same PID or
the required two tests for    powerful stuff. It will       parameter that you
a non-continuous              most likely take you a        should have your
monitor and see if it has     few times to grasp the        voltmeter, lab scopes,
passed or failed that test.   concept of how to use         scanners or whatever
                              mode six diagnostics,         hooked to.
                The           but once you have the
second part of mode six       concept down, I am sure
is where we feel the          you will find it a great
main meat of the              asset to your diagnostic
diagnosis is obtained.        challenges.
The second part not
only tells you that we                The remaining
have indeed failed a          sections of this manual
monitor but what the          are divided into
component/parameter is        Chrysler, Ford and
that is causing the           General Motor
failure to occur. Hmm,        diagnostic trouble code
imagine how cool this         help and mode six
would be on say a             diagnostics. To use this
P0440 trouble code.           manual to its fullest
                              potential simply look up
         The final step of    the mode six codes in
mode six diagnostics is       the appropriate sections              The next section
that the vehicle will tell    of the manuals and use        says what you should
you the pass/fail criteria    the following formula to      do. In other words, if
for the component it          decipher the trouble          this vehicle were in my
has flagged as being          code.                         repair shop theses are
faulty! Wow, what a                                         the steps that I would
time saver this is.                   The first section     take to diagnose this
Imagine not having to         labeled how did this          vehicle. Remember, this
look for specifications       code set, lists the driving   is only a suggestion, if
and also being able to be     conditions (enabling          you feel your way works
very confident that once      criteria) needed for the      better than by all means
the repair has been made      PCM to run the test. In       do it your way.
that it should pass the       other words, this is how
monitor the next time         you will have to drive                The final section
the PCM runs the test.        the vehicle to get the        lists what monitors were
All we need to do is to       monitor to run.               suspended if any. This
make sure that the                                          is for you to remember
specifications now fall              The next section       that there may be
comfortably within their      labeled why did this          another code set after
ranges.                       code set, tells you what      you repair the first
                              the PCM saw that              trouble code. To nip
                              caused the code to set.       this possibility in the
butt, just make sure that
the PCM passes not only
the monitor that you feel
you repairs but also all
the monitors that are
listed as being shut
down as a result of that
code being set.

       Now that we
have thoroughly
discussed mode six
diagnostics, lets get to
work and make some

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