Service Engine Soon Light: What It Means And Is It Different From Check Engine?

Out of the many dashboard warning lights that illuminate when starting or driving a modern car, the service engine and check engine lights are most often misunderstood or intertwined. Compounding the issue is not all vehicles have a service engine soon warning light. However, the law requires all cars since 1991 (1988 in California) to have an emission-controlling on-board diagnostics (OBD) system and a check engine warning light to remind drivers of possible engine, transmission, emissions, or electrical problems.

There's no need to panic if you see a red or amber "SERVICE ENGINE SOON," "SERVICE DUE," or "SERVICE SOON" warning light in your car. The light indicates the vehicle needs servicing or routine maintenance after reaching the prescribed mileage, like every 5,000 or 10,000 miles. It could also mean that the prescribed servicing is past due and will stay illuminated unless the vehicle enters service at the dealership or garage.

Unfortunately, the service engine soon warning light does not say precisely what servicing the vehicle needs. It all depends on the make or model and odometer reading. In some luxury brands, like Mercedes-Benz vehicles, cars have ASSYST (Active Service System) Plus to help drivers stay up-to-date with repairs or maintenance. The service codes typically include lettered suffixes that correspond with specific maintenance intervals.

For instance, an illuminated SERVICE A reminder means the car is due for an oil and oil filter replacement, a brake inspection, and a service indicator reset. Meanwhile, SERVICE B will include tire inspections, filter replacements, and brake tests.

The service soon indicator and check engine light are different in most cars. While the service soon warning light could only mean the car needs an oil and filter change, the check engine light could mean many things.

It could trigger faults due to a loose or failing gas cap, a misaligned throttle position sensor, or something catastrophically expensive like bad catalytic converters or a blown head gasket. It's safe to continue driving with an illuminated service engine soon light, but having a check engine light is a different story. As long as the car is running fine, you can continue driving with a check engine light, but the ultimate goal is to bring it to a mechanic as soon as possible for proper diagnosis.

On the other hand, an illuminated service engine soon light also requires a trip to the dealership or garage, but you can save money with a DIY oil change and having a scanning tool to reset the service codes. It's always best to check the owner's manual for more about routine servicing and service engine codes.