[AT] Tractor hauler question.

Stephen Offiler soffiler at gmail.com
Tue Aug 26 08:18:29 PDT 2008


On Tue, Aug 26, 2008 at 10:22 AM, Don  Bowen <don.bowen at earthlink.net> wrote:

> On some vehicles there is a very carefully defined drive sequence to get the
> monitors set.  On some is it a certain number of miles and a cold start.

It's not that simple.  There are a substantial number of monitors
(again, software routines that look for problems).  Examples include:
Catalyst Efficiency Monitor, Misfire Monitor, AIR System Monitor, EVAP
System Monitor, Fuel System Monitor, HO2S Monitor, EGR System Monitor,
PCV System Monitor, Thermostat Monitor, Comprehensive Component
Monitor - Engine, Comprehensive Component Monitor -Transmission... and
so on, depending on vehicle and model year.

The drive sequence to get a monitor to run is different for each
MONITOR, not each vehicle.  Some of the sequences are quite complex.
An example from my '03 Ford Focus for EVAP monitor:

- The Engine must have been shut off for a minimum of 6 hours
- The monitor must begin between 330 seconds and 1800 seconds from cold-start
- Intake Air Temp between 40F and 90F
- Barometric sensor minimum 22.0 " Hg indicating vehicle is below 8000
ft altitude
- Engine Load min 20% max 70%
- Vehicle Speed min 40 mph max 80 mph
- EVAP Purge Flow min 0.05, max 0.10 lbm/min
- Fuel Tank Level min 15%, max 85%
- Fuel Tank Pressure Range min -17" H2O, max 1.5" H2O

Again, each MONITOR has a different set of conditions that need to be
achieved in order for the monitor to run.  To fully appreciate this
you'd really need an indepth understanding of what the monitor is
doing, but even from the basic level you can see that some of the
conditions above are unique to the fuel/evap system.  Other monitors
don't care about things like fuel tank levels and purge flows for
example.

Steve O.



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