The service engine soon light means different things on different vehicles. On many cars and trucks, including various GM and Nissan models, it is the malfunction indicator lamp, the same warning other makers label check engine: the engine computer has stored a fault code. On some other vehicles, a separate service or maintenance light is simply a reminder that scheduled maintenance, such as an oil change, is due. Your owner manual says which one your vehicle has.
Service engine soon vs check engine light
| Light | Meaning | What to do |
|---|---|---|
| Service engine soon (fault lamp) | A stored trouble code, same as check engine | Read the code with a scan tool |
| Maintenance or service reminder | Scheduled service due by mileage or time | Do the service and reset the reminder |
| Flashing engine light | Severe misfire right now | Reduce load and stop soon |
Common causes when it is a fault lamp
- Loose or worn fuel cap
- Misfires from spark plugs or ignition coils; see bad spark plug symptoms and bad ignition coil symptoms
- Oxygen sensor faults; see O2 sensor
- Vacuum leaks and lean codes; see vacuum leak and P0171
- Thermostat and coolant sensor faults; see P0128
- Transmission faults reported as P0700
How to find out why it is on
- Plug an OBD2 scanner into the port under the dash and read the codes; see how to use an OBD2 scanner.
- Look up each code in our OBD2 codes list.
- If no codes are stored, the light may be a maintenance reminder; check the owner manual for the reset procedure.
How to turn off the service engine soon light
For a fault lamp, fix the cause, then clear the code with a scan tool or let the light go out on its own after several drives without the fault returning. For a maintenance reminder, perform the service and reset the reminder using the procedure in your owner manual, often through the instrument cluster buttons. Clearing a fault code without fixing it only hides the problem until it sets again; see check engine light and drive cycle.
Can you drive with it on?
If the light is steady and the engine runs normally, you can usually drive while you get the code read. If it is flashing, the engine is overheating, oil pressure is low or the engine is knocking, stop and diagnose before driving further; see engine overheating and low oil pressure.
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