4 JULY
2005
AIR
REPAIR Many techs are seeing monitors that can be very
difficult to complete.With persistence and following
enabling criteria exactly, we’ve found that enough
monitors can be completed in order to take an OBDII
emission test. Our shop recently encountered a 3.0 liter 1996
Caravan with some very stubborn monitors.
The van originally failed with a P0443 (evap purge solenoid
circuit). It was tested and failed six months later with the same
code. We always baseline any emission repair before doing
anything, and the odd thing we noticed was that the CAT
monitor was incomplete. All other monitors were completed
and our code P0443 was in memory.
A P0443 code indicates a problem in
the purge solenoid circuit. This vehicle
does not have a leak detection pump
and purge is monitored similar to an
OBD-I vehicle. Evap is not supported
on this vehicle; it is monitored by the
comprehensive monitor.
Our problem was that a transmission
linkage rod rubbed through the wiring
harness and power feed wire to the evap
purge solenoid. We repositioned the
harness and soldered the wire back
together.We did have to disconnect the
battery because the wiring repair was
directly underneath it. This resets all
monitor status and clears codes.No matter what we did,we could
not get this van to complete enough monitors to take the test. The
supported non-continuous monitors on this vehicle are the CAT,
O2, O2 Heater, and EGR. The O2 Monitor would set to complete
as soon as the van was started, leaving us needing one monitor to
run to take the emission test.
We have a specific route that we drive to run monitors. It
usually takes about fifteen to twenty minutes and includes
both city and highway driving.We look up the drive traces in
the NCVECS CD or Alldata, set the scanner to monitor status,
and drive until we pass enough monitors to take the test.
Eleven test drives later nothing else would complete. I got in
touch with a Chrysler representative who helped us out. His
advice was to put the van on a lift, run it up to highway speeds,
and let it coast all the way down to idle without touching the
brake.He said sometimes the monitors would run during this
long decel. We were a little apprehensive about doing it
because it had 150,000 miles on it and one of the issues was a
small cooling leak in the area of the water pump. You guessed
it, at about 55 mph the timing belt let go.During the repair the
tech noticed that the thermostat was also stuck open.
I wondered why a van would run a monitor on the lift but
not the highway. This van’s temperature gauge stayed in the
middle throughout the test drive; but we never actually
checked engine temperature during the test drive. One of the
enabling criteria for the EGR monitor was an engine
temperature of above 170 degrees F.
So our next test drive we set the scan
tool to data list and recorded it. We
only needed one monitor to run.
When we started the test drive we
were at 178 degrees F; once on the
road the engine quickly cooled off to
136 degrees F, preventing the
monitors from running. Remember,
we have to maintain 170 degrees F
coolant temperature. After a new
thermostat, the engine maintained a
steady 194 degrees F on the road. The
odd thing is that the CAT monitor
completed on the first test drive. The
van passed the OBDII emission test
without completing the EGR or O2 Heater monitors.
Ten days later the van returned for some additional
maintenance. We rechecked it, and all of the monitors were
completed with no new codes. The customer did mention that
the van heated up faster and the heater worked better.
Watching the enabling criteria closer would have saved a lot
of time.We don’t know why the O2 Heater initially wouldn’t
complete since that monitor was supposed to run within ten
minutes after the engine was shutdown.We also don’t know
why the O2 Monitor set to complete without the O2 Sensor
even getting hot.And finally, why did the monitors seem to run
out of order? But engine temperature was a critical factor for
this vehicle to run enough monitors to pass the test.
Remember ALL enabling criteria must be present in order
to run the monitors.
Damage done by 1996 Caravan transmission linkage rod.
Free Seminars Fixing IM240 or OBDII Failures Repair Facility Performance Report Touring a Test Station
Obtaining a copy of your shop’s Repair Effectiveness Report (your grade) Receiving a copy of a drive trace
Receiving a certificate for attending an Outreach Seminar ...or ANY emissions related questions!
(847) 758-3434 www.epa.state.il.us
ALL Enabling Criteria
Must Be Present to Run Monitors
By Jeff Katz,Owner; Katz Automotive, Elgin
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