Rear o2 sensor...check engine light on
Thread Starter
Drifting
Joined: Jan 2007
Posts: 1,460
Likes: 38
From: Broken Arrow Oklahoma
Rear o2 sensor...check engine light on
On my last run Saturday, my check engine light came on. I took it to get scanned and it is showing bank 1 sensor 2, which is the driver's side rear o2 sensor. My question is should I replace the sensor for about $100 or just have it tuned out? I am worried if I replace it that the same problem might happen again. I have LT's and hi flo cats and have been reading that this is a somewhat common problem. What have others done with this problem?
Melting Slicks
Joined: Feb 2004
Posts: 3,307
Likes: 111
From: Tucson AZ
Chevy uses a dual O2 sensor system on each side to test the Cats. O2 sensors operate by sensing how much oxygen is left in the mixture and outputting a voltage signal. If combustion is complete and there is no O2 left, their output is zero or flat. The front O2 sensor inputs are used for AFR changes and the rear should be flat as the CATS completely burn any excess fuel. However, for the Cats to light off, they must reach a very high temperature. This happens almost immediately in the stock system with the cats up front, but when you install long tube headers and place them downstream they take longer to heat up. When the ECU runs a cat check and the second O2 sensor output is not flat, it sets a P0430 or P0420 code meaning the Cats are not working. This usually happens before the cats have reached the light off temp. The car will still run fine; you will just be staring at the check engine light periodically.
Replacing the rear O2 sensor, will not fix it. You must tune out the rear sensors.
Replacing the rear O2 sensor, will not fix it. You must tune out the rear sensors.
Pro
Joined: Feb 2007
Posts: 741
Likes: 0
From: Austin Tx
So what exactly do you mean when you guys say "tuned out". If they are simply turned off and report "not ready" in an OBDII scan, it will fail emissions in Texas.
As of October 15th 2008, Texas emissions test only allows for one sensor to be in the "not ready" state. If rear O2s are tuned out, that means two sensors will be in the not ready state.
http://www.txdps.state.tx.us/vi/Misc....htm#Readiness
A lot of people running long tubes in Texas... hell, even LG is located in Texas. I'm curious to know if any Texas long tube guys have gotten inspected after Oct 15th.
Or am I misunderstanding what "tuned out" means?
As of October 15th 2008, Texas emissions test only allows for one sensor to be in the "not ready" state. If rear O2s are tuned out, that means two sensors will be in the not ready state.
http://www.txdps.state.tx.us/vi/Misc....htm#Readiness
A lot of people running long tubes in Texas... hell, even LG is located in Texas. I'm curious to know if any Texas long tube guys have gotten inspected after Oct 15th.
Or am I misunderstanding what "tuned out" means?
Instructor
Joined: Dec 2006
Posts: 145
Likes: 3
From: Bolivar OH
I just installed LT Headers with Cats. I got the engine control light right away. My HP Tuner Scan shows what codes are turning the light on and allows me to un checks the codes that turn on the CEL. All of mine were the rear O2 Sensors. If you leave the CEL on, you would not know if other conditions existed that were not related to the rear O2 Sensors.
Advanced
Joined: Mar 2008
Posts: 82
Likes: 0
So what exactly do you mean when you guys say "tuned out". If they are simply turned off and report "not ready" in an OBDII scan, it will fail emissions in Texas.
As of October 15th 2008, Texas emissions test only allows for one sensor to be in the "not ready" state. If rear O2s are tuned out, that means two sensors will be in the not ready state.
http://www.txdps.state.tx.us/vi/Misc....htm#Readiness
A lot of people running long tubes in Texas... hell, even LG is located in Texas. I'm curious to know if any Texas long tube guys have gotten inspected after Oct 15th.
Or am I misunderstanding what "tuned out" means?
As of October 15th 2008, Texas emissions test only allows for one sensor to be in the "not ready" state. If rear O2s are tuned out, that means two sensors will be in the not ready state.
http://www.txdps.state.tx.us/vi/Misc....htm#Readiness
A lot of people running long tubes in Texas... hell, even LG is located in Texas. I'm curious to know if any Texas long tube guys have gotten inspected after Oct 15th.
Or am I misunderstanding what "tuned out" means?
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Pro
Joined: Feb 2007
Posts: 741
Likes: 0
From: Austin Tx
Tuned out means taking it to a tuner and when they do a performance tune to the car the way you want they can also turn off the rear sensors so it reads ready at the emission site. Mine was doing like yours till I took it to FastLanes and got it tuned. Put 50 miles on the car and took it back to the site that failed it previously and it passed. That was yesterday Nov. 24th
Advanced
Joined: Aug 2008
Posts: 95
Likes: 0
From: Tucson Arizona
Yes, tuned out sensors will report as "ready" at your emissions site.
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Anyone have knowledge of using a Tech II to tune out the rear sensors? I have two customers that get this frequently on stock cars. One is an older guy who doesn't drive it hard enough to really light off the cats. I can scan & watch the mv on the 2nd scanner, after a 2 min run at 2k rpm it works fine....
Pro
Joined: Jul 2006
Posts: 608
Likes: 1
From: LZ IL
Anyone have knowledge of using a Tech II to tune out the rear sensors? I have two customers that get this frequently on stock cars. One is an older guy who doesn't drive it hard enough to really light off the cats. I can scan & watch the mv on the 2nd scanner, after a 2 min run at 2k rpm it works fine....
Can not be done with a Tech II.
