It is considered generic because it applies to all makes and models of vehicles, although specific repair steps may be different depending on your car model.
Possible Causes :
Look for missing ground strap or a rusty ground where the fuel tank is grounded to the frame. Check for damage to the wiring harness connector. You might continue by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data.
Diagnostic trouble code B0021 is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.
Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before B0021.
Fortunately, B0021 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.