The check engine light is on
The engine appears to be running okay when suddenly a 'check engine' light or an engine icon illuminates the dash panel. What's going on? Is the engine about to pack it in? Probably not, however something is wrong. The warning light generally indicates that the engine management computer has detected a malfunctioning fuel or emissions component or a system failure.
Most vehicles today have an OBD (On Board Diagnostics) Level 1 or Level 2 (1996 and newer) computer that self-tests the emission components and system operation. Isolated or one-time fault signals are eventually wiped from its memory, but persistent or serious faults are stored and trigger the warning light. Automotive technicians use a scanner or scan tool to retrieve fault codes and diagnose these computerized vehicles.
The oxygen sensor is probably the most common cause of a 'check engine' warning. However, it can be a gradual deterioration of the sensor and the driver may not notice the resulting reduction in overall engine performance. Maintenance schedules generally recommend an inspection or replacement every 50,000 to 80,000 kilometres if it's an "unheated" 1 or 2-wire sensor or every 100,000 to 160,000 kilometres if it's a "heated" 3 or 4 wire (OBD2) sensor.
A degraded oxygen sensor can increase fuel consumption by 10 to 15 percent. Definitely not what you want when fuel prices are as high as they are. Other signs that the oxygen sensor is worn out include excessive exhaust emissions, engine surging or hesitation, even premature failure of the catalytic converter.
Other problems may trigger the engine warning light to come include:
a failed sensor such as oxygen, coolant temperature, MAP (manifold absolute pressure) or airflow meter.
- engine problems such as poor performance, faulty spark plugs and wires, or clogged fuel injectors.
- emissions problems such as a loose or cracked vacuum hose, loose or missing gas cap, or a failed EGR (exhaust gas recirculation) valve.
- electrical wiring that has a short or open circuit.
How you should react to the warning light depends on how the light behaves:
If the light comes on for a little while and then goes out, you may have a momentary problem in the system.
Once the light goes out, the problem is no longer occurring but it may have caused the computer to store a diagnostic trouble code in its memory. This isn't cause for immediate action, however, you should take the vehicle in as soon as you can and have it looked at.
- If the light comes on and stays on, it indicates an ongoing problem.
It may not be a major problem however it may affect your car's performance, gas mileage and emission levels.
Definitely take your vehicle to a repair shop as soon as possible.
- If the light flashes on and off, the vehicle has a severe problem that will cause additional damage.
If your repair shop is nearby, take the car in immediately. If not, shut off the car and call for assistance.
Your owner's manual is the best source of information on maintaining your car's performance and dashboard warning lights.