At 09:13 PM 4/14/99 , you wrote:
>okay, I'm confused. I just went over to my friends house who has a 98 v6.
>Another guy he knows was there with a 99 R/T. They both just cut the cats
>off and put a piece of pipe where it was. They didn't mess with the sensors
>anything. Cranked um up and the check engine light never came on. The guy
>with the six cranked his up with the cat before he put the pipe there to see
>what it would sound like and the light didn't come on. I have 99 5.2 and I
>want to do this too. Before I do, is this normal or is something going on to
>mess up the truck behind the scenes that we don't know about.
>
When you say they "just" cut them off, did they just do it recently? If
so, give 'em some time... Firing up the engine after cutting off the cat
won't light the MIL. The engine doesn't even use the O2 sensors for about
5 mins or so. (until the conditions are present to enable closed loop
operation) Here's a list of the conditions that have to exist before the
computer checks the efficiency of the cat:
Accumulated Drive Time
Enable Time
Ambient Air Temperature
Catalyst Warm-up Counter
Engine Coolant Temperature
Accumulated Throttle Position Sensor
Vehicle Speed
MAP
RPM
Engine in closed loop
Fuel level
I'm not even sure what some of the above are, but as you can see, a lot
of conditions must be met before the cat is tested. At least 4 of those
are not present at startup (drive time, cooolant temp, vehicle speed,
closed loop). When all of the above are satisfied, the computer can run
the test. If it fails, the computer will try two more times during that
trip. If both fail, a pending code is stored. On the next trip, when all
of the above criteria are satisfied, the computer tries the test again. If
the test fails, the computer will try two more times. If both of those
fail, a code is generated, and the check engine light comes on.
Everything I know about OBD-II tells me that they will get a MIL sooner
or later, but I've heard from people who claim that they haven't received a
code, so I can't say for sure. At any rate, if they do get a MIL, it won't
be right away; it'll take some driving around...
-Jon-
.--- stei0302@cs.fredonia.edu ------------------------------------.
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