Michael Maskalans wrote:
>
> So I'm looking for a real description of this trouble code.... my FSM
> tells me:
> "left bank downstream or downstream and pre-catalyst O2s shorted to voltage"
>
> since I've got two O2 sensors, I'd assume they would be known as
> pre-catalyst and downstream. does this mean both O2s are bad or just
> the upstream? my gas milage **SUCKS** right now (unfortunately I have
> no baseline for post-SAS, so maybe it will just be that bad - that bad
> being just under 10.), so I'll be ordering a fore O2 shortly but I'd
> like to know if my downstream O2's "solution" is also being a problem.
>
> TIA,
>
Some obvious stuff here first I'd like to mention. First thing is that
the OBD II code descriptions are just BS stuff in some situations. The
fact that one code can indicate one or more possible issues. For
example - how the code says "down stream *OR* downstream and pre-cat" -
In my mind that translates into "well ya could have one bad - or you
could have two bad - I really don't know - you figure it out" Damned
manufacture BS! The freaking computer should be capable of saying
EXACTLY WHAT SENSOR is bad! its not that difficult. The damned thing
has a set of parameters to monitor right? And when one goes out of the
normal range it trips a MIL light right? So why the hell not identify
specifically what sensor is reading funky? I run into this problem
almost on a daily basis at work, when trying to explain OBD codes to
customers who come in to have their MIL and Check Engine lights
diagnosed... (end rant). They expect me to be able to tell them
*exactly* what that code means and why its on. When I tell them "could
be this, or that, or this could also cause that code" - its frustrating.
At that point I tell them to take it to a shop - that a good shop will
have a diagnostic machine that can monitor the engines functions as its
running.... Anyway...having said that, back to your O2 sensors...
The original function of the O2 sensor was to monitor the A/F ratio to
keep it at an optimal mixture. Then the manufacts. got the great idea
to stick another O2 sensor after the CAT to monitor how well the CAT is
working. What I am left wondering is - does the post-CAT sensor ONLY
monitor CAT efficency? Or does the ECM pull data from BOTH the up and
downstream sensors to moderate the A/F ratio?
Only full proof way to know is to monitor the signal coming from the O2
sensors themselves at normal operating temps. You would need to know
what the voltage range is supposed to be for the sensors, then use a
multimeter to monitor. Unfortunatly I don't have the specificaton data
for the sensors for your truck.
At this point - I can't really think of anything more to say - partially
because my brain seemed to not wake up this morning even though my body
was moving around all day. I really think I am loosing what brains I
ever had. Just one of those days...
-- ----------------------------------------------------------------- Attention Infidels: I am your official DBDoMPfIWUMOT! Terrible Tom -- AIM & Yahoo Name: SilverEightynine http://members.aol.com/silvereightynine/
This archive was generated by hypermail 2b29 : Mon Nov 01 2004 - 10:47:43 EST