The EVAP is a system designed to store fuel vapors in order to prevent them from escaping into the atmosphere. The EVAP has a vented canister or tank that stores these vapors, until such time as they can be completely burned under the proper conditions.
Some EVAP systems include an electronic pump that detects leaks and generates pressure within the system so that flow or leak detection can be verified. Leak detection reference orifices are also included in the system and are usually in-line to ensure an accurate flow rate reading with the pump running. The PCM uses the input signal from the system sensors and the reference from these orifices to calculate if the leak detection performance is adequate.
When set the P043F OBDII fault code is due to, the detection of inconsistencies in the EVAP leak detection reference orifice caused by excessively high flow.