Will I Get a "Check Engine" Light If I Install This Exhaust Part?

Some aftermarket exhaust parts replace factory catalytic converters. The WRX comes with as many as three cats, and the ECU can be quite particular about what it sniffs downstream of these catalytic devices.

If you replace ANY of those stock cat pipes with either "offroad" (no cat) versions, or with aftermarket catalytic converters, you MAY get the P0420 "Check Engine" light (CEL). Or you may not. It depends on a lot of factors, including your driving style, the number/type of cats on the car, and the particular nature of your car and its ECU.

If you remove ALL the catalytic converters, you DEFINITELY will throw the P0420 code sooner or later.

We can't guarantee that any aftermarket exhaust part (except cat-back or axle-back parts) will NOT throw the catalytic converter code. Even downpipes with aftermarket catalytic converters MAY result in the CEL! Use these at your own risk, and know that you might have to deal with the codes.

Also note that if your car is subject to emissions inspection, it WILL fail if there is an active CEL. In addition, even if there are no active codes, the "readiness states" (internal self-tests the ECU performs) may not be triggered. Your safest route for passing state emissions testing is to use ALL factory catalytic converter hardware. Once you start deviating from factory, it may be more of a challenge to pass current or future tests.

Also be aware that there are various KINDS of aftermarket catalytic converters. Some have a federal registration number on them and are certified for repair use. Some are the same type as the certified ones, so the function the same, but they are NOT federally registered. Some are just plain old high-flow catalytic converters with a focus on high flow at all costs. Aftermarket manufacturers use different kinds and types of cats, and can change those over time. You may want to understand more about your local and state emissions inspection process before you purchase an aftermarket catalytic converter.

Give us a call if you have more questions.