Car engine sensors monitor the various engine functios as well as other conditions present in the engione. These conditions are monitiored by thre car engione computer. The condions monitered by the car computer includet tire pressure engine temperature oxygen entering the engine as well as various other engine condioins, These sensors function normally until they go out of range What this means is thaT they are no longer capable of monitring their intended area. When this happens the check engine light goes on on the cars dashboard. Older cars thosae made prior to 1996 are called OBD 1 on On Board Diagnostics 1. There aree many diferent ways to hook into the cars computer.For exam[le ther are 2 differnt readers for Chrysler cars and trucks 2 for Ford cars and trucks as well as the same for GM cars. Asian cars such as Toyota Honda Nisssan Hyundai aslo had various ways to read the engine codes. Then in 1996 tjhe Federal Dept of Transportation made all car manufacerers standarize the way data was retrieved from the car computer. OBD 2 was started, that is all cars and light trucks used the same 16 pin data retrieval now found in the passenger area. Most are located near the underside of the steering wheel. After using the scan tool to retrieve the engine code the nechannic shiuld use either a service manual or a computer based program such as AllData or Mitchell. In these methods are specific steps on how to locate and remove the affected sensor the mechanic must use the scanner to reset the check engine light. These are the general steps used you shoukd consult a sevice book or online program for more specifed intructiions.