I have a 2003 LS series Trailblazer 4WD with a 4.2L engine. It has
44,000 miles on it, so far it only needed one part, still under
warranty, the engine... Well, It has been a year since the engine was
replaced, going to work the other day the check engine light came on.
I took it to advance auto parts and they put it on the machine to get
the error codes out of it. It came up with error code P0172, System
Too Rich. I pulled the old one out and checked it for continituity,
it is a 4 wire unit, the heater checked OK and then I put a volt meter
across the sensor lines and heated it up a little with a propane
torch, it never read over .065 volts. I thought it might be the O2
sensor, so, I picked one up. They gave me a Bosch 15285. I took out
the old one and when I was putting in the new one I noticed that it
didn't have any slits on the side like the original. I tried it in
the opening and it fit, so, I put it in. Well, the next day the check
engine came on. I thought the the computer module may need cleared so
I disconnected the battery for half an hour or so and hooked up the
battery, Check engine light came on after 20 or so miles. I know that
it may be something else. I had the check engine come on one time
because the gas cap was loose. My question would be is the Bosch
15285 the proper sensor for the upstream sensor? Is there any cheap
error reading units out there on the market?
As always, Thanks in advance,
The code is telling you the pcm sees a rich mixture, not necessrily a bad
sensor, a full scan should be done to properly diagnose the problem, many
things can cause the rich mixture to the point the pcm cannot adjust with
it's maximum fuel trim programming and sets a code.
Yes, 15285 is the correct sensor in the upstream position.
Thing is, reading the trouble code is only 5% of the diagnostic
process, although, if all you're interested in is swapnostics,
you'll be fine.
Did you use a high impedance volt meter when you tested with the
Yes I did use a impedance volt meter, I do electronic repair and used
one of my Fluke meters. I did some more reading about o2 sensors.
Found a good article about o2 sensors at.
I'm stuck at home today, couldn't do any testing today.
I'll keep you posted on what I find with the latest code. In the
repair business they call it shotgun repair, of course, 5 bucks for a
fist full of capacitors is a lot cheaper than these sensors.
On Sat, 30 Sep 2006 13:56:57 GMT, aarcuda69062
Hey Ahole, you can make a coment without getting nasty. ALso I do
question that comment because they have not relaxed the 5year 50K
emission standard as you suggest and they are tlking about extending
it in the future. In order to sell a car they have to certify it to
meet emissions for this period above, not just for 24K miles.
Why do you think it is an O2 sensor problem? Too rich could be any number of
things. O2 codes would be in the 130-167 area. Just getting a code is really
of little value. You need to hook it up to a scanner and see how everything
is interacting. Pull the freeze frame data and see just what was going on
when the code was set. I would think a 172 code would be more of a leaking
or dirty injector.
Being stuck home all day I did some research. Looks like a canister
problem would cause this sort of problem. I'm interested about the
dirty injector suggestion, see, I had a Astro van years ago. It had a
throttle body fuel injector. Funny thing, my Trailblazer is acting
just like my Astro van. I made up a tube that was bent so that I
could pull out the dog house and remove the air cleaner. I would just
spray the face of the injector with carb cleaner and clean out the
crap coating the inside of the carb and it would run like a top. I
realize that those days are gone. I really never messed with the
injectors on this beast yet. It looks like the driver for the
injector is mounted right on the injector. Is there an injector for
each cylinder? I can't see under the air box on top of the engine.
Years before that I had a 1973 Chevy Nova that ran like a dog, had it
to the shop plenty of times, I found the problem to be a cracked
vacuum line. It dried out and had a crack in it. I found that by
accident. It ran like a top after I fixed it, My Nova had a 350 in
it, I miss it.
On Sat, 30 Sep 2006 23:56:42 GMT, "calhoun"
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