A simple resistor will not work - the post-cat O2,
as you surmise, is just there to check that the cat is
working properly. If the computer doesn't get a reading
which corresponds properly to the pre cat O2, within
a certain boundary, it will still set a code
Also the post-cat sensor can have a small effect on A/F
ratio. As the computer detects the cat degrading it will
alter the a/f mixture slightly to try and prevent clogging of
the cat.
What you really need is an "o2 simulator" - it sounds
like this is already been covered in the mentioned
"KatBox" - what I am assuming this is.
Chris Bennight
http://www.slowcar.net
http://charger.slowcar.net
----- Original Message -----
From: "Ragnarok" <yum@yermom.org>
To: <dakota-truck@buffnet.net>
Sent: Sunday, July 15, 2001 3:39 AM
Subject: Re: DML: Aft O2 'simulator'
| Bob Tom wrote:
|
| > An owner of a '99 Dak is looking to remove his cat.
| > Anyone know of some sources for a fix to the aft
| > O2 sensor problem? TIA.
| >
|
| I just took the cat off my 97 and while preparing to do this, my buddy
| and I brainstormed and this is what we came up with: the aft sensor
| doesn't actually affect how the engine runs, it's just there to satisfy
| OBD2 laws, to double-check that the cat is working. when properly
| functioning, it passes a voltage of between 100 and 900 millivolts,
| averaging 400. Logically, this is slightly lower than the sensor
| upstream of the cat. Less oxygen, less voltage. So in order to create a
| false reading after the cat is gone, wire in a resistor in the negative
| lead that will drop the voltage just enough, say 250 millivolts, 1/4
| volt. Offhand I don't know how many ohms that is, not much I'd assume.
| You must leave the sensor in the exhaust because it only functions
| properly at its operating temperature of around 600 degrees.
| HOWEVER, after taking the cat off my truck, it runs great, hasn't
| thrown any codes, and the check engine light hasn't come on. *shrug*
| Haven't touched the sensors.
| Oh, and the exhaust is noticeably louder. ;-)
|
| William
|
|
|
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:02:06 EDT