I (kinda) agree on the codes...but they do point the tech in the right
direction. Remember though...you always look at what caused the code to
appear, not just replacing the part (sensor).
I've seen those types of codes come up and people just replace the
part...code still comes back.
This code actually translates to: O2 sensor circuit - high voltage (Bank 1
Sensor 2). That would be the Left bank/Downstream. More than likely, the
sensor is shorted...but check the harness and make sure it hasn't rubbed
itself on something and grounded out (seen that happen).
Hehehehe...and we all have those days. ;)
- Bernd
-----Original Message-----
From: owner-dakota-truck@bent.twistedbits.net
[mailto:owner-dakota-truck@bent.twistedbits.net] On Behalf Of Terrible Tom
Sent: Monday, October 25, 2004 10:33 PM
To: dakota-truck-moderator@bent.twistedbits.net
Subject: Re: DML: DTC P0138
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...
This archive was generated by hypermail 2b29 : Mon Nov 01 2004 - 10:47:43 EST