* Oxygen sensor: The oxygen sensor measures the amount of oxygen in the exhaust gas. If the oxygen sensor is faulty, it can cause the engine to run rich or lean, which can lead to the service engine soon light coming on.
* Spark plugs: The spark plugs ignite the fuel in the engine. If the spark plugs are worn out or fouled, it can cause the engine to misfire, which can lead to the service engine soon light coming on.
* EGR valve: The EGR valve recirculates exhaust gas back into the engine. This helps to reduce emissions, but if the EGR valve is stuck open or closed, it can cause the engine to run poorly and the service engine soon light to come on.
* Catalytic converter: The catalytic converter converts harmful pollutants in the exhaust gas into less harmful substances. If the catalytic converter is damaged or clogged, it can cause the engine to run poorly and the service engine soon light to come on.
If the service engine soon light is on in your 1994 Buick LeSabre, it's important to have it diagnosed by a qualified mechanic to determine the cause. Driving with the service engine soon light on can lead to further damage to the engine and more expensive repairs.
