Technical Service Bulletin WVU31R — 2007 SUBARU IMPREZA

2.5 Liter N/A engine only. REVISED. Subaru of America, Inc. has determined that vehicles affected by this Service Program require ECM reprogramming. A modification to the Engine Control Module software logic has been developed to improve the performance of the emission control system. This software change will not adversely affect fuel economy or performance. This software update is intended to improve vehicle emissions when the vehicle is operated in cold weather and the engine is turned off and restarted within short periods of time such as in several minute intervals. The A/F sensor contains a heating element, which is controlled by the ECM, and which assists the sensor in reaching an optimum temperature, resulting in better accuracy. When the vehicle is operated under the conditions described above, there could be a longer than desired delay in the ECM?s turning on the A/F sensor heating element, resulting in higher than desired emissions. This software enhancement will correct that condition.