There are hundreds of Ford engine codes, or on-board diagnostics, but some of the more common ones encountered are P0455, P1000, P1131, P0171 and P0102. A vehicle's on-board diagnostics is its way of communicating any issues found during self-diagnosis. Under the on-board diagnostics system, all light duty card and trucks must monitor specific systems and use generic codes to indicate any problems that are found.
On-board diagnostics help a technician determine what is wrong with the vehicle by narrowing down the possible causes. The codes are either generic or manufacturer-specific. Engine codes with a format of P0XXX are generic codes and common across different manufacturers, whereas codes in the format of PXXXX are manufacturer-specific.
An example of a common generic engine code is P0455, which indicates that a gross evaporative emission control system leak is detected. The possible causes for this code are a missing, loose, open or dirty fuel filler cap, a leaking fuel tank, or a leaking evaporative system. In addition to the engine light coming on, a noticeable fuel odor is common with this problem. An example of a common Ford-specific engine code is P1131, which means that the upstream heated oxygen sensor switch has detected a lean system on bank one. This is caused with either a faulty oxygen sensor, a vacuum leak, a fuel injector problem or a cylinder misfire.