2000 CHEVY MONTE CARLO 3800. SERVICE ENGINE SOON. A SCAN FOUND NO CODES.  ENGINE WAS CLEANED, FRONT HUB ASSEMBLES WERE CHANGED. THE SERVICE ENGINE SOON LIGHT IS ON, BUT THERE ARE NO CODES SHOWING UP ON THE SCAN TOOL. I AM THINKING THIS IS THE EMISSIONS OR MAINTENANCE  REMINDER TO HAVE THE ROUTINE SERVICE DONE. HOW TO RESET?

Answer: Your vehicle does not have a routine service or maintenance light or indicator, nor does it use the service engine light for that purpose. I assume the scanner is working properly and has been checked on another vehicle. To clarify, is this the service ENGINE light, or the service VEHICLE light?

VISITOR:It is the service vehicle soon message.

There are many different computer systems on today's cars. the service ENGINE indicator is strictly powertrain computer related. Service VEHICLE codes are stored in the body control module. The service VEHICLE indicator can be caused by several different systems. Anything from vehicle lighting, to security system, to body control module(BCM), to ABS (but usually an ABS light as well), powertrain non-emissions related codes, or communications problems between any of these computers. Most inexpensive scanners only read the power train computer. In order to read codes that set a service vehicle  light, you would need a higher level scanner that can read BCM codes and ABS and others if needed. About the only thing that can be done without having the BCM scanned is to be sure to check all fuses.

THE RADIO WORKED FINE UNTIL I CHANGED THE BATTERY. NOW IT IS LOCKED. HOW DO I UNLOCK RADIO.

The radio replacement may very well be the cause of your service vehicle light. After replacing a radio, the system must be set up with a dealer scanner. Audio system option, VIN #, etc, need to be set up in the radio and the BCM. If not done, this will cause several different body codes, and is most likely the cause of your service vehicle light. If the radio says LOC, then you need a Radio Unlock Code.