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<wenmang@yahoo.com> wrote in message
news:1158541726.366596.263700@i3g2000cwc.googlegroups.com...[color=blue]
> Ray,
> I have more questions to ask before I carry out O2S readiness drive
> test:
> 1) I bought a OBD2 reader(INNOVA) from WalMart, so far following
> Monitor icons are complete on my car:
> O - O2 sensor monitor
> OH - O2 sensor heater monitor
> Plus all other monitors except following one that is not done:
> C - catalyst monitor which is currently blinking(not ready)
> I am confused about "catalyst monitor", is it related to the drive
> cycle we are talking about?[/color]

Probably, yes.
[color=blue]
> 2) what does it mean "Vehicle is in closed loop"?[/color]

The O2 sensors only provide valid readings if A) the O2 sensor is working,
B) the O2 sensor is warmed up, C) the vehicle is fully warmed up, and D) the
engine is not operating at wide open throttle (WOT) or close to WOT.

Since the O2 sensor only provides valid readings if all of the conditions
are met, for the conditions where all of those conditions are not met, like
when the vehicle is first started or under heavy acceleration, the computer
ignores O2 sensor output and relies on input from other sensors to determine
how much fuel to mix with the air.

When the computer is using O2 sensor output, the system is referred to being
in "closed loop" mode because it looks at O2 sensor readings to adjust the
air-fuel mixture, then looks at the result of the mixture adjustment, then
does the same thing over and over. The engine is operating most efficiently
fuel-consusmption and emissions-wise when the system is in closed loop. In
order to speed up the warmup process, the O2 sensors have heaters built in,
and the automatic transmission will not shift into overdrive until the
coolant temp is sufficiently warmed up.

In all other operating conditions, the system is referred to as being in
"open loop" because it is operating without O2 sensor input.
[color=blue]
> 3) what is definition of one driving cycle?[/color]

One driving cycle is one trip where the car is started and driven so that
every sensor monitored by the OBD II system has sent a valid signal to the
computer. Many OBD II diagnostic trouble codes (DTC) have a 2-trip
detection logic where it has to see the same fault for 2 consecutive trips
before it sets the malfunction indicator light (MIL, or check engine light),
and if it does not see the fault for 2 consecutive trips, it will turn off
the MIL.

The conditions that determine what counts as a "trip" or driving cycle vary
by vehicle, but they generally require a cold start, driving at various
specified speeds for a specified lengths of time, with the coolant temp
rising to a specified amount and the transmission shifting up and down
through all the gears for a specified amount of time, then parking the car
for a certain amount of time, then repeating the trip.
[color=blue]
> 4) since only "catalyst monitor" is no ready, should I skip the O2S
> monitor(first couple of steps from techinfo.com seems for front O2
> test) and directly go to the "rear O2S readiness monitor"(the one
> using gear 2)?[/color]

Yes. The catalyst monitor is the O2 sensor that is after the catalytic
converter.[color=blue]
>
> I like to make sure that I understand everything correctly before I do
> the test and I am not sure what stage my car is at.
> Thx.
>[/color]

--

Ray O
(correct punctuation to reply)