Yes, but he could also twist the cap a few more clicks because the Check
Engine light is on and think that he cured the problem. Maybe he read
somewhere that the Check Engine light usually comes on because the gas cap
is not seated properly, which is true but ignores the hundreds of other
reasons that the Check Engine light might come on.
He could scan for codes, but he refuses to acquire a scan tool. If he had
the scan tool, he could reset the computer and turn the Check Engine light
off, and all of this discussion would never happen.
it wouldn't apply to an ancient beast like a 97 A-Star but on modern
vehicles the PCM will run a quick-test on the EVAP after each "refueling
event". That's how the those new gas cap lights get triggered vs. the
the more ya know!
It is part of the OBD2 spec - and it is a requirement in order to make
SURE that nobody can "cheat the system" The computer in the car is
doing a very complex check on several hundred different parameters,
and validating the response to be sure all the sensors are there,
reporting, and accurate. The fact that the evap monitor WILL reset
itself after you put the gas cap on is really a concession to the
owner - he does not need to pay a dealer or garage to reset the
computer - yet it maintains the integrity of the epaporative emission
control check for the EPA.
Now, since MOST jurisdictions allow ONE monitor to fail and still
pass the smog test, you COULD reset the codes and get all the
monitors except the evap set (can be done in less than 15 miles)
andSTILL pass with a faulty evap system - but with your luck it would
reset as you pull in for your test, and the light would come on - and
you would fail. (assuming you had an unresolved evap problem)
Used to be they did a cap check as part of the test - but not any
You are entirely right, except that they allow one or two monitors to not be
complete and still let the test proceed. You said they allow one to fail,
but they really allow one to be incomplete -- still running.
There is a subtle difference in a monitor that has failed, as you said, and
is not complete yet. If the monitor has indeed failed, then it is compete
and did not pass the self-tests that you described. If the self tests have
not finished running, that is the condition for which the vehicle can still
be submitted for testing.
I'm not sure about the allowance of one or two monitors still running. When
I had this issue, they let me test with two still running, but I get a mixed
explanation as to whether they still allow two or only one, or if they allow
two for cars that are older and one for cars that are not so old. But, you
are also correct here, most (if not all) jurisdictions that test for smog do
not require that all monitors be finished running the tests.
I know I can reset it with a code reader. Was hoping there was a way to do
it with a jumper instead of disconnecting the battery.
No, there is not. Whether you do a hard reset with a scan tool, disconnect
the battery (which the specification says is not supposed to reset) or
simply drive the vehicle until the computer recognizes that the condition
has been cured, it still takes the same number of drive cycles to set the
readiness monitors to ready, or complete (which is the proper term).
or using the diagnostic tool?
After driving for a couple of weeks, the light went out. Then a few
days later came back on. Then a couple days later went off again. I
will venture down to the auto parts place today and get the code. Yes,
I don't like rushing into anything. LOL!!
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