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2004 Ford GT - Service Engine Light

Why the service engine light got turned off it will not light up at all. I just brought the car

Do you mean it doesn’t turn on with the engine off, but the key is in the “on” position? If so the most likely causes are (1) blown fuse, (2) the dash warning light bulb is burned out, (3) the bulb has been removed, (4) the battery is dead, or (5) there’s a wiring or ECM circuit board problem.

We get comments here from time to time where a seller has removed the bulb or done some other dastardly deed to make sure that light doesn’t turn on, b/c selling a car with the CEL on is hard to do. They hope the buyer doesn’t notice it also fails to come on before starting the engine.

In most places, auto parts stores will read the codes for free. I suggest doing that right away to see if any codes are currently set.

The Ford GT wasn’t produced as 2004 model year vehicle. Do you have a 2004 Mustang GT? It’s not uncommon for some unscrupulous sellers or dealers to remove the check engine light bulb if the car has a fault (or modification) that triggers it constantly. For example if someone installed some catless headers and didn’t reconnect the O2 sensors, that would certainly cause the check engine light to stay on. And for some states a check engine light being on is an instant-failure. So people simply disconnect the light.

That’s why they check to see that it lights up during the initial bulb test. I suppose you could slip this by some less detailed inspectors but I wouldn’t count on it.