If you have tried everything and still engine light comes up, in some vehicles specally variants of ford, the main computer might need to be reprogrammed to get rid of the engine light re-appearing after part replacement. If this be the case, just other symptoms like air conditioner compressor shutting down. Not many dealers or mechanics would understand or know how to reprogram the main computer. Although it might be a bit expensive, but better to check in with an authorized ford dealer who is skilled to reprogram the main computer. Please don't rely on the dealer who suggests that you need to replace the main computer or nothing can be done without double checking.