Air Repair: January 2005

              Category Two - A specific monitor or
group of monitors will not run. Many
times this situation occurs because the
system has determined that there is a
problem in something that is used in the
diagnostic procedure. For example, a bad
O2S heater will prevent the O2S monitor
from running. If the O2S monitor does
not run, then the CAT monitor will not
run. If one of the monitored systems relies
on another monitored system to function,
then a difficulty (DTC) interrupts the
sequence.You might see in this case a DTC
and insufficient monitors run. Repair the
vehicle and after the DTC is removed the
sequenced monitors now run. The
illustration shows a vehicle with a bad O2S
heater. The heater monitor has run,
generated a DTC and shut down
everything that uses the O2S as an input.
Category Three - No monitors run.
This may sound bizarre but does happen
every so often. It appears that if certain
components are slightly beyond normal
criteria, the PCM might prevent the
monitors from running until the
component is replaced. We have seen
examples of O2S’s preventing all
monitors from running and yet the
vehicle has no O2S DTC’s. Should this
happen? Probably not, but oh well....
continued on page 4
What Do We Know About OBDIINow?
By Al Santini
C O N T E N T S
  What Do We Know About
OBDII Now?
  2005 Outreach Seminars
  Santini Gives Seminars to
IEPA and Envirotest Personnel
  How to deal with OBDII
Canadian Vehicles
  Gloves in Automotive, Truck
and Body Shops?
VOLUME 8  NUMBER 1
JANUARY 2005
management functions that were present
in OBDI. The design of OBDII is
supposed to allow independent testing of
emission functions with the ability to
identify failures that might allow the
vehicle to produce in excess of 150 percent
of the Federal Test Procedure. Without a
doubt it is doing exactly this. Technicians
that attend the OBDII seminars indicate
that vehicles that have the MIL
illuminated or commanded on do have
something wrong and can be fixed to a
level that will allow the MIL to be
commanded off by the PCM. There has
been virtually no false MIL’s on vehicles. If
the MIL is on - there are fixable problems.
Once they are fixed the MIL will be
commanded off. The system is doing
exactly what it was supposed to do.
However, readiness or lack of monitors
run remains an issue. Currently 16
percent of the retested vehicles are rejected
because of insufficient monitors run.
These vehicles fall into one of three
different categories:
Category One - A couple of monitors
remain unset. Frequently these vehicles
require some specific driving conditions
to get the monitors to run. The customer
just does not drive the vehicle in the
“correct” manner. An example of this is a
person who does not drive the vehicle at
highway speeds. It is likely that the
Catalytic Converter monitor might not
run. The technician will be required to
drive in a very specific manner paying
attention to speeds and loads that will
allow the monitor to run. Note: Don’t
forget running a monitor is what allows the
system to generate a DTC.No monitor = no
diagnostic trouble code generated. The CD
that is given out at the OBD seminars helps
greatly by identifying the driving conditions
required for monitor completion.
Illinois has been testing OBDII
systems with pass fail criteria
for about a year now, and we
know much more about how the
system works or does not work
than we knew in January 2004. But
first a quick review...
A vehicle that is presented for an
OBDII test will first receive a gas
cap test and then be scanned
through the DLC. The vast
majority of the vehicles will in fact
communicate via the DLC and
most that will not are either
missing B+ on pin 16 and/or
ground on pin 5. If the vehicle will
communicate via the DLC, a check
of applicable readiness monitors
will occur. If the correct number of
monitors have been run, MIL
function is analyzed and the
vehicle passes or fails. This
abbreviated explanation gives an
overview of the test. More
information is available in the
Outreach OBDII seminars.
So what do we know about the
test after months of testing
thousands of vehicles? The first
item of interest is the system is
doing exactly what it was designed
to do. Remember that OBDII is an
emission testing strategy that
includes most of the engine
CODES DESCRIPTION STATUS
CAT Catalyst Efficiency Status: NOT READY
CATHEAT Catalyst Heating System Status: Not Supported
EVAP Evaporative System Status: Not Supported
AIR Secondary Air System Status: Not Supported
AC Air Conditioning Refrigerant Status: Not Supported
O2S Oxygen Sensor System Status: NOT READY
O2SHEAT Heated Oxygen Sensor System Status: Ready
EGR Exhaust Gas Recirculation System Status: NOT READY