post cat 02 sensor

**Riowrx** · 04-07-2011 05:15 PM

My stage 2 09 wrx w/. high flow cat keeps throwing a too lean code and setting off the cel every 200 miles. i have extended the sensor out of the main flow which helped but the problem still exists. I was wondering if anyone knows how to fix this problem.

**Donkey** · 04-07-2011 06:21 PM

Do you not have engine management?

**zax** · 04-07-2011 06:31 PM

Also, are you running an intake?

**Riowrx** · 04-07-2011 07:03 PM

stock tuned ecu and perrin CAI problem existed before the CAI was put on.

**Anub1s** · 04-07-2011 07:18 PM

"Stock tuned ecu", so no engine management then? That's your problem right there. You're risking engine damage right now using an aftermarket down pipe with no real engine management. Also, your set up may be in line with Cobb's stage 2, but you aren't technically there unless you have been tuned.

**Riowrx** · 04-07-2011 07:38 PM

The car has been tuned on a dyno buy my local sport garage. They know what there doing, because i am no tuning expert. It runs no differently when the cel comes on. They told my the sensor is just tripped off by the high flow cat.

**Anub1s** · 04-07-2011 08:04 PM

Originally Posted by Riowrx

The car has been tuned on a dyno buy my local sport garage. They know what there doing, because i am no tuning expert. It runs no differently when the cel comes on. They told my the sensor is just tripped off by the high flow cat.

Okay I see what you're saying now, the stock ECU has been tuned, good good. The shop MIGHT have not disabled all of the normal DTC' that is disabled for that set up. I would consult them about it.

Incidently which code is it? If it is a system too lean code, it isn't your rear O2 sensor. P0171?

That code is usually associated with MAF problems, and leaks in the intake tract post MAF.

**Riowrx** · 04-07-2011 08:20 PM

i believe that it is p0171 or p0420. its for how efficient the cat is working. Im sure its the cat given the problem started after the initial tune when the downpipe (cobb) was installed.

**Anub1s** · 04-07-2011 08:31 PM

Double check the code and let us know what it is, because they are two very different DTC's which require two very different fixes.

P0420 is the standard cat efficiency code that is disabled with every stage 2 tune, if the guys who did your tune didn't disable it, you need to take it back to them and have them correct it. It's a very standard and basic thing, and hopefully they know it and it just slipped their mind, otherwise I would rethink who you take your vehicle to.