When testing my car's emissions,
what does a "not
ready" result mean?
Carmen’s Question: "I'm
hearing a lot about vehicles failing their emissions
test for "not ready" issues, can you explain what that
means and how it can be fixed? My vehicle is a 1999
Pontiac Grand Am.”"
That’s
a great question, and one that is becoming more and
more common over the past few years.
First, let’s take a minute to understand just what
is involved in vehicle emission testing here in Arizona.
Older cars are tested under a standard called IM 147.
IM 147 is the enhanced test used for most 1981 through
1995 gasoline-powered vehicles in the metro Phoenix
inspection program. In this test, the vehicle is driven
on rollers (called a dynamometer) at varying speeds
to simulate urban driving. The exhaust is continuously
measured and the results are shown in grams per mile.
On newer cars, an On Board Diagnostics (OBD) test
is used. In this type of test, used on 1996 and newer
light duty vehicles, engine operating data is accessed
by connecting directly to a computer in the vehicle
that continuously monitors engine emission control
systems operation. The on-board diagnostic test does
not measure tailpipe emissions.
One of the challenges encountered with this type of
test is that the cars computer must be in “ready” status
before the test can be completed. These computers on
most cars will be in “ready” status when you arrive
at the test center, but not always. If your car fails
for a “not ready” condition, the most common cure for
this is driving. Lots of driving. You should drive
the car under various conditions; both freeway and
city for a couple of days before returning to have
it retested. Then on the day you’re going to take it
back, make sure to drive at least 20-25 minutes at
various speeds before pulling into the test facility.
When you get in line at the test center, don’t shut
the engine off as this may cause some of the readiness
flags to reset to not ready status and then you’ll
have to start all over again.
If you still have a readiness problem after following
this advice, then you may want to contact your AAA
Approved Auto Repair facility to have the car checked
out or to receive more specific and detailed instructions
for your particular model.
