2015 Mustang GT emissions problems..

[junits15]

I don't believe I have long tube headers on the car?

You should check, that cat code combined with the o2 sensor codes is almost always caused by them being shut off for LTH.

it could be stock cats with the code shut off as well

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[fastblackcar]

The headers are absolutely causing you to fail, I bet your tune disables the rear O2 sensors entirely, which IMO is a foolish method to "tune out" cats. Buy some J-style non foulers and put them on the rear o2 sensors. Drive for a while and see if that works. If that doesn't work then you need to go back to the stock tune, which will require you to put that IMRC back together or else you'll fail for that.

This is why i think disabling the rear O2 sensors is foolish, it makes it impossible to pass a plug in test. All it does is prevent the CEL, which would have been enough to pass emissions 30 years ago but hasn't been in a while.

I have no clue at this point. I am going to have the GT350 removed and keep it stock. Never want to deal with this again.. I'm just so lost.

 

[2015 Silver GT]

Post a picture of your car from underneath to first determine if you have headers. That way you can eliminate that as one reason for the failure.

 

[fastblackcar]

Post a picture of your car from underneath to first determine if you have headers. That way you can eliminate that as one reason for the failure.

Stock cat welded back on.

 

[BullittBoy]

I doubt it is related to the GT350 intakes. GT350 pass emissions, Bullitt's (which also use that intake) pass emission. It is tune related more than likely OR your cats are failing or have failed, but I would think you would see P0420/0430 codes if they are bad. I would be very suspect of the tune.

 

[fastblackcar]

I doubt it is related to the GT350 intakes. GT350 pass emissions, Bullitt's (which also use that intake) pass emission. It is tune related more than likely OR your cats are failing or have failed, but I would think you would see P0420/0430 codes if they are bad. I would be very suspect of the tune.

What would you recomend? I contacted the tuner from the previous owner, a pro shop, he said he wasn't sure at all, no help there. I so contacted another shop in my town, wasn't very helpful and gave me a shitty tune, lost money there so, dead in the water still.

 

[fastblackcar]

Another option instead of going back to the stock tune, would be to get your tune updated so that it doesn't mess with the rear o2 sensors at all, then when you put the spacers on he rear o2 sensors everything will work.

I don't have LTH on the car, stock underneath. I contacted a performance shop and they said it sounds like the Rear O2s are disabled and that they would verify they are off before turning them on. I told them everything I said here and them seem to understand. I'm curious if it is my tune, or the Rear O2s are really off and that's been the problem for MONTHS. You can look underneath the car here on the forums. Please provide your thoughts, you have been so helpful.

 

[Zenaxia]

just go to a shop that will pass you, they charge a bit more but if you ask around someone knows a guy, if you dont want to do that the factory tune will work as long as you revert to stock parts, if you have no cats or o2 sensors that are moved from factory then you can use 02 sensor spacers that bypass the emissions logic, best of luck!

 

[2015 Silver GT]

just go to a shop that will pass you, they charge a bit more but if you ask around someone knows a guy, if you dont want to do that the factory tune will work as long as you revert to stock parts, if you have no cats or o2 sensors that are moved from factory then you can use 02 sensor spacers that bypass the emissions logic, best of luck!

So you’re asking a shop to commit a federal crime? That’s not smart.

 

[Zenaxia]

technically its not because his emissions devices are working as intended, his ECU is just not recalibrating and its much better than repeatedly trying to pay for new tune files and parts chasing a ghost issue.

 

[geep81]

just go to a shop that will pass you, they charge a bit more but

That's not how it works in Ohio.

 

[Zenaxia]

well if you pay lund like $100 im pretty sure they can delete those codes off the ecu for you permanantly

 

[2015 Silver GT]

technically its not because his emissions devices are working as intended, his ECU is just not recalibrating and its much better than repeatedly trying to pay for new tune files and parts chasing a ghost issue.

Yes that is totally illegal.

well if you pay lund like $100 im pretty sure they can delete those codes off the ecu for you permanantly

So are you saying Lund is committing federal crimes? You do know they were already heavily fined for this very thing.

 

[geep81]

well if you pay lund like $100 im pretty sure they can delete those codes off the ecu for you permanantly

Did you learn that on TikTok or perhaps you Grokked it?

 

[geep81]

So are you saying Lund is committing federal crimes? You do know they were already heavily fined for this very thing.

To be fair, sounds like you are saying it too.

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