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2014 mustang v6 check engine light

7242 Views 17 Replies 5 Participants Last post by  scottydsntknow
I have a 2014 mustang v6. I have a cai borla s type. I purchased bbk catted x pipes and installed them today and my check engine light came on. The code I got back said it was from the o2 censors. My question is will getting a tune or new o2 censors make the cel go away? Also, is it bad to use the car for a few months with the x pipe without a tune? Any help is appreciated!
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Check to make sure that the connectors for the O2 sensors got plugged in all of the way when the exhaust was installed.
The computer will default to the open-loop fuel setting if it cannot receive information from the O2 sensors. It won't necessarily do any harm if driven that way for a short period of time, but engine performance and fuel mileage will suffer if the computer never goes into the closed-loop fuel setting.
I don't think that a tune is required for any of your modifications, so there is something else wrong.
Re-inspect the work that was done recently first.
I should also add when taking the censor off the stock pipe it was very difficult to get off due to how tight it was. The bolt of the outside got stripped down while trying to take it off. I also noticed that some of the wiring was messed up. It’s not extremely messed up but some of the wiring was exposed from one of the casings so I put electrical tape over it. Could that be causing the cel? I hope that makes sense I’m very new to all of this. Should I get new censors, a tune or get an oxygen censor restrictor? Besides the wires I saw and the bolt getting damaged I’m pretty sure they were plugged in properly although I will double check them. I did not install them myself but I was a helping hand for the process.
Yes. If the sensors are damaged that could be the cause of the code.
I recommend using only OEM Motorcraft replacement sensors.
Make sure to remove the negative battery cable before starting the work.

Hopefully, that will solve your problem.
Good luck!
How long can I drive it with the engine light on? It should effect the engine should it?
That catted x-pipe is most likely your problem. Aftermarket cats have fewer cell counts vs the OEM cats hence the CEL. Either put the stock one back on or get a tune to turn off the rear o2's. But be warned turning those off is not so easy anymore because tuners are no longer doing it. Also if emission testing is done in your area then you are in for a fight.
Could I drive it with the cel and not have to worry about other issues?
The only thing to worry about is the engine will run with a richer than normal air fuel mixture when it is in open-loop. This can contaminate the catalytic converters.

I am assuming that the code is being caused by the O2 sensors that are located in front of the catalytic converters (upstream). If the code is related to the sensors that are located behind the cats (downstream), it is more likely that the cause is related to the high flow cats, as Grabber suggests.

If you post the codes, we can possibly narrow down the cause of the CEL.
P0135 Is the code I got. Someone suggested I get spacers to trick the ecu and the light will go off.
Once again I did notice some wiring coming out of the harness so I put electrical tape over it for now. Wasn’t too bad, the censor did get beat up a little trying to take it off. Not sure if the outside force damaged the inside of it or not.
P0135 suggests that there is a problem with the bank 1 sensor 1 O2 sensor. That is the sensor on the passenger side, nearest to the exhaust manifold, in front of the catalytic converters. That is one of the O2 sensors that are referred to as the 'upstream' sensors. The upstream sensors are necessary so that the computer can measure the air/fuel ratio and adjust the fuel trims so that the engine will run properly.
The sensor 2, 'downstream' sensors are located after the catalytic converters. Their only purpose is to measure the emissions output of the engine, and to trigger a CEL in the event that they detect emissions beyond a preset parameter. The engine doesn't need them to run correctly, and they are the ones where people use various schemes such as spacers to try and fool the computer into thinking that there is less emissions being put out by the engine than there really is.

If it is the O2 sensor on the passenger side, nearest to the engine, that was visibly damaged during removal, the odds are that is your problem.
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ill go ahead and try out a new censor if that doesn’t work I’ll try the spacer or a tune. I have a feeling one of those 3 things will work. Should I do an oem replacement for the censor? Thank you to everyone helping it’s much appreciated!
If P0135 is the only code, a spacer or a tune will not help with your present problem.
It is likely a problem with the sensor itself, or the wiring/connector associated with that particular O2 sensor. And one other thing, since this code appeared after working on the exhaust, a reasonably good sized exhaust leak on the passenger side of the engine can also cause this code to appear.
Those are the most common causes.
And yes, OEM Motorcraft is the safest bet for a replacement sensor.
If I end up getting an after market sensor does it matter if one is oem and one isn’t?
As long as the sensor is working correctly, the computer doesn't care if it is OEM or aftermarket.
I had this happen when I put on my kooks long tubes. My drivers side sensor was damaged when removing the old exhaust manifolds. I replace that 1 with a NTK and fixed it. The spacers are for downstream O2 sensors. I had to use some if those as well to get rid of my cel. Good luck!


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Get a tune. Stop trying to bandaid it. If you are going to mess with these cars then you need to be prepared to pay to do it right. If not, sell it and buy a Honda.
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