P1170 and P0171 after front pipe install
 

2013 Scion FRS

I recently replaced the front pipe from OEM to catless. I did literally nothing else besides that. After a ~5 minute drive the CEL popped up with P0171. I was a bit confused but reset it thinking it was a fluke. Drove two days without it coming back on and the car felt normal. Today it came back on again with P1170 added on to it. Car seems to idle a bit rough now.



I'm running a catless header and OFT but that has been on for over a year with no issues. It has a GrimmSpeed CAI but that has been on before I brought the car nearly 2 years ago. Those are the only mods outside of the front pipe.

I've tried searching but not much comes up. P117B seems to be a common code to go along with these two but I lack that.

I suggest you take a log with your OFT and see why it thinks you're running lean. Or perhaps reflash your tune.

I got the same issue it's because of the CAI. I put it back to stock intake with K&N drop in filter and problem solved. It's because the CAI with Catless you need a custom tune from OFT

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Check your exhaust system for leaks. Pay particular attention to the header-overpipe and overpipe-frontpipe connection.

I suggest using a shop-vac with blowing function and soapy water:

https://www.youtube.com/watch?v=IZknLjq0PVI

LTFT is at ~39% which is bad right?

That's what I had... Also, my other experience was exhaust leaks between sensors. It would also make it at 39%

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O2 sensor AND a vacuum leak... sounds like an exhaust leak to me.

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What do you know you are correct. Turns out a whole ass nut came off my header and another one was loose. Learned that you should invest in good tools and not just hope you got it tight enough. I still have a minor leak around the gasket but my fuel trims have returned to normal so I'm gonna call it good enough until this weekend.