By researching the “enabling
criteria” necessary to run monitors for
the EGR, HOS2 and CAT monitors, I
found they all require a minimum
ambient temperature of 19 degrees F.
Also, the OBDII Misfire Counter
was not functioning. This vehicle, as
with most others, must “learn” the
specific electrical characteristics of the
crank sensor, the crank sensor air gap,
the machining characteristics of the
crankshaft tone wheel, and so on.
Chrysler calls this learning process the
Adaptive Numerator. There is a drive
cycle consisting of a series of vehicle
decelerations required to perform this
learning process for this particular
vehicle. Some brands of vehicles can
perform this learn function in the
shop bay. Only research will reveal the
proper procedure for the subject
vehicle in your shop. Without
Guidance,We Are Lost. The scan tool
readout stated the vehicle did not
complete the Adaptive Learn
procedure, hence the misfire counter, a
continuous component monitor
(CCM) was disabled. In researching
the enabling criteria for the Misfire
Monitor, I learned it also would be
disabled due to the ambient
temperature requirement of 19
degrees.
While researching the wiring
diagrams and component locations
guide, I saw there was a temperature
measurement thermistor located
behind the left headlamp housing. It
was a three- wire sensor called the
Battery Temperature Sensor. The
calibration error had suspended the
running of all monitors except the
continued on page 2
C O N T E N T S
OBDII Readiness Case Study
Transmission Codes
2005 Outreach Seminars
Setting Monitors That Defy
Standard Methods
Another Way to Explain
Monitors to your Customers
VOLUME 8 NUMBER 2
APRIL 2005
Once I got involved at Outreach’s
request, I contacted the repair facility
and the customer directly to get the
information I needed to repair the
vehicle. Using my scan tool to check
the OBDII system, the only monitor
that was complete was the HO2S
monitor. This monitor is enabled at
idle after a cold start with engine
temperature below 127 degrees F and
battery temperature within +/-27
degrees of engine temperature. I
wondered why that monitor ran and
no others did?
When eyeballing long lists of live
sensor data, it is easy to overlook key
pieces of information while trying to
rationalize every value displayed. But I
did notice the Ambient/Battery
Temperature Sensor was sending an
erroneous very cold signal of -7.6
degrees F. On a 70 degree F day, this
was a red flag.
The owner of a 1998
Chrysler Cirrus, with a
2.5L engine and A/T,
SMPFI, and odometer at
91,000 miles informed a service
manager of an OBDII
emissions test reject because of
monitors. The inspection
reports showed the service
manager that the vehicle had
been rejected at the test station
seven times over a five-month
period. Setting monitors
during normal driving wasn’t
an issue since a cross-country
trip was taken during that five-month
period. The repair
facility scan tools also
confirmed the test station
monitor status report. Many
unsuccessful things were tried,
including the installation of a
remanufactured PCM, and the
technician driving the vehicle
according to drive trace
procedures also accomplished
nothing. Finally the vehicle was
returned with instructions to
“drive the car for a few days.”
The customer departed more
frustrated than ever.
SENSORS
CURRENT ADAP CELL ID: O
ENG COOLANT TEMP DEG: 73.4F
ENG COOLANT TEMP VOLT: 2.59V
INTAKE AIR TEMP DEG: 68.0F
OBDII Readiness Case Study
by Angelo Vitullo, Emissions Program Instructor,Automotive Technology Department;
St. Louis Community College, Forest Park Campus
OBDII MON
DISABLED STATUS
OBDII MON DISABLED LoTemp: YES
OBDII MON DISABLED LoBatt: NO
OBDII MON DISABLED LoBaro: NO
