Clear a check engine light by disconnecting the battery cables and turning on the headlights to drain all of the electricity from the system. This makes the vehicle's computer perform a hard reset and extinguishes the check engine light. However, if a problem is present and detected by the computer, the check engine light is turned back on. Other options are to fix the problem or have a professional mechanic reset the onboard diagnostic computer.
The check engine light can be a sign of no problem or a minor problem, but it can also indicate a major malfunction that can cause serious damage to your vehicle if it is not addressed. Different vehicle manufacturers assign varying problems to the check engine light. It can indicate problems with engine speed, fuel mixture, transmission shifting, powertrain problems that impact vehicle emissions and many other issues.
Visually inspect your vehicle immediately for any obvious major problems should the check engine light illuminate. Look for other dashboard indicators such as low oil pressure or overheating that require pulling the car over and shutting it off immediately.
Tighten the gas cap, and reduce the vehicle's speed and load until you can reach a facility and have the error code read professionally. This costs a small amount of money compared to a major mechanical failure.