Detecting Exhaust Leaks

If you are getting a P0420 or P0430 code for catalytic converter efficiency below threshold, one of the potential problems is an exhaust system leak. Since your exhaust has pulsating pressure waves, there are periods when a leak can pull outside air into your exhaust system and cause the catalytic convertor to have a high oxygen output and pull these codes.

One way to find small leaks is to pressurize the exhaust while the engine is cold and spray it down with soapy water. To pressurize the exhaust system, plug up the exhaust pipe with a large socket wrapped in a rag or duct tape and hook the blower end of a shop vac to the intake. This should allow you to detect leaks by looking for bubbles from the soapy water.