Jim Grant's Tech Tips
‘02 Buick Century, Too Many Warning Lights
The “Service Engine Soon" light on my dash stays lit. This light came on soon after the Change Oil Soon" light appeared. Is this a dangerous condition? "
In your case, about the only relationship that the “Service Engine Soon” and “Change Oil Soon” lights is that they’re on the dash. Your vehicle has a computer system that lets you know when to change the engine oil and filter. This is based on engine revolutions and engine temperature and on a maximum mileage of 10,000 miles. Under severe conditions, which most of us drive, the indicator comes on well before 10,000 miles. Because the system performs its calculations on driving conditions, the mileage that the warning light turns on at can fluctuate noticeably. For the system to work properly, you must reset the computer every time the oil is changed. It is not uncommon for the reset procedure to be overlooked if the warning light is not on at the time of service. So, you’ve got to reset the system to get it to work correctly. The reset is easy, turn the key on, but don’t start the engine, push (to the floor) and release the gas pedal three times within five seconds. If you did it right the Change Oil Soon should flash, which means the system is resetting. Turn the key to off after the light has finished flashing, then start the vehicle. If the light comes back on, the system has not been reset. Just repeat the procedure. The “Service Engine Soon” warning light is a different story. That warning light is the vehicle’s engine computer letting you know that something is not right. There is no resetting this warning light with a hokey pokey move. You’ll need to have a technician plug into your vehicle’s computer. The computer will provide a diagnostic trouble code (DTC) with a brief system fault description. Once that information is obtained, diagnosis of the problem can be performed.