P0500  Vehicle Speed Sensor Malfunction 
P0501  Vehicle Speed Sensor Range/Performance 
P0502  Vehicle Speed Sensor Low Input 
P0503  Vehicle Speed Sensor Intermittent/Erratic/High

P0400  Exhaust Gas Recirculation Flow Malfunction 
P0401  Exhaust Gas Recirculation Flow Insufficient Detected 
P0402  Exhaust Gas Recirculation Flow Excessive Detected 
P0403  Exhaust Gas Recirculation Circuit Malfunction

P0300  Random/Multiple Cylinder Misfire Detected 
P0301  Cylinder 1 Misfire Detected 
P0302  Cylinder 2 Misfire Detected 
P0303  Cylinder 3 Misfire Detected

P0200  Injector Circuit Malfunction 
P0201  Injector Circuit Malfunction – Cylinder 1 
P0202  Injector Circuit Malfunction – Cylinder 2 
P0203  Injector Circuit Malfunction – Cylinder 3

P0100   Mass or Volume Air Flow Circuit Malfunction 
P0101  Mass or Volume Air Flow Circuit Range/Performance Problem 
P0102  Mass or Volume Air Flow Circuit Low Input 
P0103  Mass or Volume Air Flow Circuit High Input

All modern vehicles has a computerized engine control systems. Those systems have a certain amount of built-in self diagnostic capabilitys to detect problems that can affect engines performance and emissions or fuel saving. The same is for the antilock brake system, stability control system and other onboard systems that are connected to vehicle computer and controlled by this computer.