* To reset the radio: This usually involves holding down certain buttons on the radio itself for a specific time (often the power button and a preset button simultaneously). Consult your owner's manual for the specific procedure for your radio model.
* To clear a trouble code (check engine light): This requires a scan tool (OBD-II scanner) to read and clear the diagnostic trouble codes (DTCs). Auto parts stores often offer this service for free. You cannot clear trouble codes without a scanner.
* To reset the Electronic Control Unit (ECU): This is generally *not* recommended unless specifically instructed to do so by a mechanic while troubleshooting a serious problem. Disconnecting the battery for a period of time is sometimes used, but improper execution can cause further problems. This should only be done if you have a specific reason and understand the risks.
* To reset other systems (e.g., tire pressure monitoring system): Some systems have specific reset procedures. Consult your owner's manual for instructions on resetting specific systems. For TPMS this usually involves driving for some time at a steady speed after inflating tires to correct pressure.
In short: You need to be more specific about what you are trying to reset. Your owner's manual is the best resource for specific instructions on resetting various components in your 2005 Chrysler Pacifica.
