Service engine soon light

my “service engine soon” light has been on for a couple of days. I checked the gas cap and no problem there. The truck runs great. Does this mean I need a new catalytic converter? What happens if I don’t get one?

That light can indicate a multitude of problems that are more serious than a loose gas cap and less serious than a bad catalytic converter. Unless you have the stored trouble codes read, nobody–including mechanics and those of us in this forum–could possibly know which of the scores of possible problems are actually taking place with your engine.

Go to Auto Zone, or Advance Auto, or O’Reilly, or (possibly) Napa in order to have the OBD system scanned for trouble codes, and then come back to this thread to post the codes for further guidance. I suggest that you bookmark this thread so that you can locate it again.

And, when you come back to post those codes, please be prepared to give us the other details that really matter, namely:

Model year
Engine type
Odometer mileage
Transmission type
Maintenance history (in detail) of this truck–at least for the past 2 or 3 years

Without all of the details, nobody can give you a helpful answer.

Thanks for the reply and suggestion. I did find an Advance Auto fairly close to home and went there today. Their scanner doesn’t show codes but said there is a small leak in the emmisions evap system. The vehicle is an 03 Frontier,4cyl. 5 speed with close to 93,000 miles on it. Other than regular oil&filter changes I think the only work on the engine has been new plugs around 80,000 and belts around 70,000. They turned the light off and said it was no big deal. Maybe try replacing the gas cap which I didn’t do yet as I could see no cracks in it. Guess I’ll wait and see if the light comes back on?

“service engine soon” light

Some cars have a service light that indicated that some form of maintenance is due and would have nothing to do with a gas cap.  There are also CELs.  CELs are Check Engine Lights.

 That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.

Gordon, I hate to tell you this but the code reader at Advanced Auto will not tell you there is a small leak in the evap. emissions system if there is not a code. What they use is a coder reader not a scanner. A scanner has more functions and can actually trigger different solenoids and such for real diagnostic work. And did you read your owners manual if the service engine soon light came on there is a code. This is right from the manual:

Service Engine Soon - Malfunction Indicator Lamp (MIL)
If this indicator lamp comes on steady or blinks while the engine is running, it may indicate a potential emission control malfunction. The malfunction indicator lamp may also come on steady if the fuel filler cap is loose or missing, or if the vehicle runs out of fuel. Check to make sure the fuel filler cap is installed and closed tightly, and that the vehicle has at least 3 gallons of fuel in the fuel tank. After a few driving trips, the lamp “Service Engine Soon” should turn off if no other potential emission control system malfunction exists.

The malfunction indicator lamp will come on in
one of two ways:

  • Malfunction indicator lamp on steady “Service Engine Soon” An emission control system malfunction has been detected. Check the fuel filler cap. If the fuel filler cap is loose or missing, tighten or install the cap and continue to drive the vehicle.
    The “Service Engine Soon” lamp should turn off after a few driving trips. If the “Service Engine Soon” lamp does not turn off after a few driving trips, have the vehicle inspected by a NISSAN dealer. You do not need to have your vehicle towed to the dealer.
  • Malfunction indicator lamp blinking “Service Engine Soon” An engine misfire has been detected which may damage the emission control system. To reduce or avoid emission control system damage:
  • do not drive at speeds above 45 MPH
    (72 km/h).
  • avoid hard acceleration or deceleration.
  • avoid steep uphill grades.
  • if possible, reduce the amount of cargo
    being hauled or towed.
    The malfunction indicator lamp may stop blinking and come on steady. Have the vehicle inspected by a NISSAN dealer. You do not need to have your vehicle towed to the dealer.