Just a few questions today:
1. If I normally drive at a 7000-foot elevation, can spending a few days at
2000' cause my Check Engine light to come on? If so, what'd be the cause?
2. If I normally drive in a non-polluted area selling ordinary gasoline, can
refilling a tank 1-2 times with gas designed to produce low emissions due to
being in a large city with pollution problems cause the Check Engine light
to activate? The cause?
3. About once a year, my Focus (2001 ZTS-USA model) has its check engine
light come on. From reading my manual it seems that once on, the light will
remain even after the cause for the light's illumination has been
removed--and that it takes three cold start cycles to reset the light to
"off". They define a cold start cycle as starting a cold engine, then
warming to operating temps in mixed city/highway driving. Rather than take
the car into the dealer if the light goes on, I'll wait the full 3 or so
cold start cycles to see if the light goes off before taking the car in for
a diagnosis--so far, the light's always gone off on its own. For me, this
wait can easily mean a week of driving before I meet the 3-cycle reset
interval. The question is then--assuming the car drives/acts/sounds normal,
is this wait-and-see approach the best?
4. Refer to 3, above. Assume the Check Engine light comes on due to a
one-time event which immediately goes away. It would seem to me that I'd be
best served by resetting the light to "off" shortly after it goes on, then
watching to see if it comes on again, indicating that service may be needed.
For speed of service and for peace of mind before waiting for the full
3-cycle reset to occur, I'd like to reset the light myself. Does this seem
reasonable? If so, is there a way under the hood or in the passenger
compartment with ordinary tools to reset the light to "off"?