What is the CEL fix?
It stops the rear CEL code P0420 Catalyst System Efficiency Below Threshold from appearing, this code being caused by the lack of a catalytic converter in the downpipe. This is usually fixed with a Pony Express MIL Eliminator or similar fix. Ensure you obtain the correct type for your model year as there are two types: 02/03 and 04. The 05+ does not currently have an electrical fix. Another fix is the mechanical fix, which works on all models. ***NOTE*** There are two CEL fixes for the WRX, the other one is the 2.2 KOhm 1/2 watt resistor. It is used to combat the CEL code P0546 = Exhaust Gas Temperature Sensor Circuit Malfunction (High Input) in the uppipe. This notice, though not important to this thread, acknowledges there are two “CEL fixes” and defines them individually to avoid possible confusion.
