How to clear trouble codes?
The best way to erase trouble codes is to use a scan tool. The tool communicates with the vehicle computer and tells it to erase the codes. It does not alter any other learned settings that should be retained for normal vehicle operation.
The worst way to clear codes is to disconnect the battery. In older vehicles (those made before 1996), disconnecting the battery even for a few seconds, or removing the power fuse for the engine computer (PCM) will erase the codes, along with all of the other learned settings the computer has stored over time.
Note: Clearing the codes will not keep the Check Engine light off. Sooner or later, the codes will reset and the Check Engine light will be back on unless the problem that caused the code to set in the first place has been diagnosed and repaired.
Caution: Disconnecting the battery to clear codes on many 2006 and newer vehicles is NOT a good idea because it may cause the PCM to forget critical settings. This may have an adverse effect on the operation of the transmission, climate control system and other functions. This, in turn, may require special "relearn" procedures using a factory scan tool or professional grade scan tool to restore proper operation of the affected systems.
Note: Clearing codes with a scan tool, or disconnecting the battery will also reset all of the OBD system monitors back to zero, meaning your vehicle won't be accepted for an OBD plug-in emissions inspection until all of the monitors have run and completed.