What are the causes of the engine malfunction indicator light coming on?
2 Answers
Reasons for the engine malfunction indicator light to come on: 1. Sensor damage, poor contact, or signal interruption can cause the engine malfunction indicator light to illuminate; 2. Poor engine maintenance, so it is recommended to perform regular maintenance and maintain good driving habits, otherwise it will increase the engine's operating burden; 3. Poor quality fuel and engine oil. If not added as required, it will cause engine wear over time, leading to the engine malfunction indicator light coming on; 4. Engine spark plug failure, ignition coil failure, fuel pump failure, fuel line blockage, etc. When the engine's air-fuel mixture burns incompletely or the mixture in the cylinder is too rich, the car may experience symptoms such as knocking and shaking.
Last month, my engine malfunction light came on, which scared me into pulling over immediately. After checking, it turned out the oxygen sensor was faulty—this part monitors exhaust emissions, and when it fails, the light activates. Other common causes include aging spark plugs causing unstable ignition, insufficient fuel supply from the fuel pump leading to incorrect air-fuel ratios, or a clogged catalytic converter causing excessive emissions. Sensor failure is the most frequent issue, and replacing one isn’t expensive; but if an ignition coil fails and causes a misfire, it could cost a lot to fix. If the light comes on, it’s best not to keep driving—use an OBD scanner to read the trouble codes, pinpoint the issue, and then have it handled by a professional shop to avoid engine damage.