Can Exhaust Sensors Be Turned Off?

[norrin302]

I purchased my GT500 a few weeks ago, and love the hell out of it. The thing is a monster!! But twice now I have taken it to get the emissions tests, and twice it has failed because they don't get a reading from 3 monitors when they plug it in. At first they told me to drive it for 80-100 miles or so to reset the sensors, but I did that and brought it back the 2nd time with the same result. The monitors that are the issue are the Catalyst (CAT), The Oxygen Sensor, and the Heated Oxygen Sensor. The car is definitely not stock (mods in my sig), but unfortunately it didn't come with a tuner. As far as I can tell, there is a catted midpipe in there. Could there be a custom tune that turns off those sensors for some kind of performance gain? Would I need to buy a tuner and a custom tune and replace what's on there? Thanks.

 

[stkjock]

SCT defaults the rear O2s to off, if the tuner doesn't turn them on then your car fails, it causes a cascade effect for 3 monitors to be not ready.


yes you will need to buy a SCT and get a tune to get around this issue

 

[RedVenom48]

You may have to bite the bullet so to speak and have it retuned locally. If yiu bought it tuned with no tuner provided, you may hsve no other option. Also, if its just an obd2 check that's one thing. Long tubrses and catted mid pipes are an instant fail for the visual inspection of the smog check in CA. A catted midpipe with longtubes might be legal in your area, but if you require oem "replacement equipment", performance exhaust may be a nono for the check. All depends on local smog laws.

 

[norrin302]

SCT defaults the rear O2s to off, if the tuner doesn't turn them on then your car fails, it causes a cascade effect for 3 monitors to be not ready.


yes you will need to buy a SCT and get a tune to get around this issue

So you're saying the tuner CAN turn off the o2 sensor, and if it turns off, it will cause the others to act as if they're off as well? And buying a programmer and a custom tune will fix this issue?

 

[VNMOUS1]

Buy a sct x4 and a custom tune. Your monitors CAN and SHOULD show "ready". That's all OBDII testing looks for.

 

[ShiftyThePirate]

I purchased my GT500 a few weeks ago, and love the hell out of it. The thing is a monster!! But twice now I have taken it to get the emissions tests, and twice it has failed because they don't get a reading from 3 monitors when they plug it in. At first they told me to drive it for 80-100 miles or so to reset the sensors, but I did that and brought it back the 2nd time with the same result. The monitors that are the issue are the Catalyst (CAT), The Oxygen Sensor, and the Heated Oxygen Sensor. The car is definitely not stock (mods in my sig), but unfortunately it didn't come with a tuner. As far as I can tell, there is a catted midpipe in there. Could there be a custom tune that turns off those sensors for some kind of performance gain? Would I need to buy a tuner and a custom tune and replace what's on there? Thanks.

I'd assume as with any car that isn't "crazy advanced" you can just buy o2 simulators and screw them and plug them up. Kinda an e-z way around the hassle, my buddy did that on his GTR and BRZ, passes all emissions as it "mimics" it though, it really isn't there (kinda need them if you do a cat delete)

 

[stkjock]

So you're saying the tuner CAN turn off the o2 sensor, and if it turns off, it will cause the others to act as if they're off as well? And buying a programmer and a custom tune will fix this issue?

yes they can be turned off and often are.

if you do in-fact have rear O2s, then yes a custom tune with them turned on should fix the issue.

of course you will need to do a driving cycle (in the manual) after you load the new tune

 

[ZeroSVT]

Facts,

SCT values files do not default the Rear heaters or o2's to off.

If you have the rear o2's turned on, there must be catalyst between the Front and Rear sensors for Readiness.

o2 simulators do not do the trick 80% of the time for emissions readiness.

Cheers,
-Matt

 

[norrin302]

There's definitely cats on the car, although they are high flow. Is there a benefit to turning off the o2 sensors? Some sort of performance gain? Could I purchase an unmarried tuner with a custom tune and install it on the car, or do I need to get the dealership to put it back to stock first?

 

[JimIII@jdm]

There's definitely cats on the car, although they are high flow. Is there a benefit to turning off the o2 sensors? Some sort of performance gain? Could I purchase an unmarried tuner with a custom tune and install it on the car, or do I need to get the dealership to put it back to stock first?

New Jersey was one of the first states to adopt the new emissisions testing. It is now an all OBDII check, no visual inspection required or tail pipe sniffer. We deal with this issue every day.

Often when installing longtube headers and high flow cats you may see a check engine light appear for catalyst efficiency. Code #s P0420 and P0430 are often most associated with this. In order to prevent these codes whoever is tuning your vehicle may shut the rear 02 monitors off in order to prevent these codes from appearing. In doing so your 02 catalyst, 02 heater, and 02 sensor will go into a "Not Available" or "Unsupported" which will not allow the OBDII to give a reading. So where are years ago this would pass a state inspection it will no longer today. If a system shows as Unsupported, Not Available, Not Ready it will fail. You are only allowed 1 of those showing and can still pass in NJ, some states may vary.

So this brings us back to your tune. Obviously right now the tune has the rear 02 montiors turned off. There for you need them turned back on with a new tune. If you get a P0430 or P0420 code appear before you get the car through a drive cycle and bring it to inspection you will Fail again. So What you can do to prevent these codes is A) Return your Exhaust back to Stock B) MIL eliminators, which I believe are illegal and not sure how people are getting away selling them. C) 02 Non foulers, we use these as a sheild to keep the sensor from seeing too much air flow and allowing it to build temp and activate before the P0430 and P0420 codes appear.

We use the 02 Non foulers here and sell them on our site for $50 drilled and modified to fit a Ford 02 Monitor. http://www.teamjdm.com/02-exhaust-bung-extensions-non-foulers-for-off-road-use/

JimIII

 

[stkjock]

Facts,

SCT values files do not default the Rear heaters or o2's to off.

If you have the rear o2's turned on, there must be catalyst between the Front and Rear sensors for Readiness.

o2 simulators do not do the trick 80% of the time for emissions readiness.

Cheers,
-Matt

well then SCT has changed how they set up the value files.

In 2007 for a FACT, my 06 gt with a Vortech and stock long block and factory exhaust got the exact messages on rediness as the OP. The tuner who set the car up told me after having the issue with 3 other car and speaking to SCT it was a FACT that SCT defaulted the O2s off.

He updated the tune to turn on the O2s and the car passed without issue.

There's definitely cats on the car, although they are high flow. Is there a benefit to turning off the o2 sensors? Some sort of performance gain? Could I purchase an unmarried tuner with a custom tune and install it on the car, or do I need to get the dealership to put it back to stock first?

IIRC - hi-flow cats sometimes require the tune to be updated to allow a longer "warm up" time for the O2s (not the best way to describe it - but I don't recall the more technical terminology)

O2s usually get turned off when there are not cats.

you should not need a reflash to stock, the SCT will see the tune in the car as "stock"

 

[ZeroSVT]

well then SCT has changed how they set up the value files.

In 2007 for a FACT, my 06 gt with a Vortech and stock long block and factory exhaust got the exact messages on rediness as the OP. The tuner who set the car up told me after having the issue with 3 other car and speaking to SCT it was a FACT that SCT defaulted the O2s off.

He updated the tune to turn on the O2s and the car passed without issue.

Yea, SCT re-did value files once in 2009, and then again this year (2014).

Its now a separate value file that you have to apply.

Cheers,
-Matt

 

[norrin302]

Ok, thanks for the help guys, you've been very informative. I'll go buy a tuner and a custom tune with the o2 sensors on, flash the Shelby, and see where I'm at at that point. If I get the P0420 and P0430 codes, then I'll pick up the 02 non foulers as Jim suggested.

 

[stkjock]

just be sure you have rear O2s on the car