Check engine light + Cats

[HoLLoW25]

Hey Guys,

Sorry to ask this question as im sure its been asked several times but i cant find a definite answer after searching for an hour.
I was look to remove the cats from my 2011 GT and know the check engine light will come on. Besides a tune if i were to put the original stock cats back on to pass emissions will the light automatically turn off after driving it for a bit or will it need to be erased? If it does turn off about how long would i need to drive it before it does?

Thanks in advance

 

[travelers]

If you remove the cats you need a tune to turn off the aft O2s. If you put the original cats back on you need to put the stock tune back or an emission tune, in to have the aft or rear O2s turned back on. There is a start and stop driving cycle for about 50 miles. Most will reset the readiness in the computer, but some may need more miles.

 

[redfirepearlgt]

If you run the factory tune with the cats off you will run rich and flag a CEL. Pretty certain the car goes into cat protection mode which is not a limp mode btw. A friend of mine has been running this way for some time. The aftermarket tune as you state will resolve that issue. Putting the cats back on will require the factory tune to be loaded at which time it should reset the CEL. If running the factory tune without the cats like my friend does and you put the cats back on, IF it does not reset itself, you should be able to go to almost any auto parts store, tell them you have a CEL and they will scan it and offer to reset it for you. Any cheap hand held scanner should also be able to do this if you choose to buy one. A friends SCT may also be used just to look at the CEL and reset it. I borrowed one to check a CEL at NMRA event one time and reset it. Married only deals with tunes being loaded not using the CEL diagnostic. Hope this helps.

 

[HoLLoW25]

Alrighty, I really appreciate the information! Thanks for taking the time.

 

[07 Boss]

If you run the factory tune with the cats off you will run rich and flag a CEL. Pretty certain the car goes into cat protection mode which is not a limp mode btw. A friend of mine has been running this way for some time. The aftermarket tune as you state will resolve that issue. Putting the cats back on will require the factory tune to be loaded at which time it should reset the CEL. If running the factory tune without the cats like my friend does and you put the cats back on, IF it does not reset itself, you should be able to go to almost any auto parts store, tell them you have a CEL and they will scan it and offer to reset it for you. Any cheap hand held scanner should also be able to do this if you choose to buy one. A friends SCT may also be used just to look at the CEL and reset it. I borrowed one to check a CEL at NMRA event one time and reset it. Married only deals with tunes being loaded not using the CEL diagnostic. Hope this helps.

Why would no cats make you run rich? Cats should have no bearing on your fuel trims.

 

[redfirepearlgt]

No they do not. Never said they did. However because of the lack of the Cat being present AND running on the STOCK TUNE the fore and aft O2 sensors on bank 1 and 2 are now seeing similar readings which they should not if the cats were present and scrubbing the exhaust as they are designed. This causes issues which flags a CEL. AGAIN AS I UNDERSTAND IT THE CAR GOES INTO CAT PROTECTION BECAUSE OF THIS AND ADDS ADDITIONAL FUEL TO ATTEMPT TO COOL THE CATS (WHICH ARE NOT NOW PRESENT) BY BURNING RICHER.

 

[travelers]

That's why if you use a Off Road X or H you need a tune to turn off the aft O2s. Or you end up with the above problem with the stock tune.

 

[Grabber Blue 5.0]

Why would no cats make you run rich? Cats should have no bearing on your fuel trims.

On the 2011 up cars they do. It's called COT Protection.

 

[redfirepearlgt]

Cat protection strategies have been around as long as having four O2 sensors on the exhaust system. The point of the rear O2 sensor is to monitor cat efficiency. This is why CEL's are generated even on 99-04 GT's that had off road pipes put on them if the rear O2's were not turned off through a tune or bypassed in some other manner.

Either way modification of the catalytic system requires some form of correction to how the PCM responds to what will be seen as poor or nonperforming data from the rear O2's due to the lack of Catalytic presence which will correct the CEL and strategy being put into effect by the PCM based on the stock tune.