I was coming back from class on the interstate (664) when i decided to fuck with some of my turbo timers features. It has a 40-whatever timer to time your pulls from 40 so i decided to go from 40-120. I hit about 115 and *boop*..on the comes the check engine light. I scan it and it read (sorry for spelling) "catalyst effeciancy below threshold" and since the cat is brand new im pretty sure the O2 went out on it. Its a 02 WRX and i JUST installed a invidia turbo back with the catted downpipe and it ran fine for about a week with multiple test pulls to check for leaks, then this happens.

Is this a common problem with other suby owners? Or other people in general? Will the bad O2 fuck up the cat or make the car run shitty (ie. rich or lean)?

 

What was the code that came up, P0???

 

Dont forget your up pipe has a catilist in it also. My friends just blew on him an all the shit went into his turbo.

 

It's the rear O2 sensor. The cat in the downpipe is not as efficient (therefore not as restrictive) as the stock one. So the rear O2 sensor is triggering the code.

The front O2 sensor is before the cat in the uppipe, so that wouldn't be causing it unless something is wrong with the engine.

 

Agreed, you're getting an out-of-range value from the rear O2 most likely. There are various (usually a little ghetto) fixes for this, look around the nasioc forum and you'll probably find a few. Aftermarket cats are rather different from stock, and the ECU is tuned for the stock cat. You could always get rid of the rear O2 and put a bypass in place of it..

 

I got one of the resistors for mine and never saw another CEL from the rear O2. And mine was with a catless downpipe.

 

hmmm...good stuff...would i be better off just getting a wideband?

 

Same thing that happens in the LSX world. After putting on my Kooks headers w/ high-flow cats etc I'd get a CEL once every few weeks for catalytic converter inefficiency. The cat is flowing more and the rear o2 picks that up and doesn't like it.

The rear o2 simply monitors that the front one is working etc so when I got my car tuned the rear o2s are simply turned off in the PCM.

 

hmmm...well i have a catless uppipe goin in so will this further fuck up the problem? Im so confused. I have people tellin me im gunna need a resistor for the uppipe, but theres two holes....one for EGT and one for the O2??? do i plug them both? answers would be awsome. Im still learnin the redicioulus exhaust setup on my car and what im gunna need to do to avoid CELs. Heres the setup....Invidia N1 with CATTED downpipe, and a Catless Uppipe with 2 bungs. What needs to be done to ensure there will be no CELs?

Edit: Also im goin for an ECU reflash once the uppipe is installed. Will that fix the lights?

 

Depending on the reflash software, you may be able to fix the lights, yes. The front O2 sensor isn't going to like the lack of cat in the uppipe, so it may be responsible for the code also. Talk to whoever will be doing your tuning and see what options are available.