Why does the engine fault light come on after starting the car?
3 Answers
Here are the detailed reasons why the engine fault light comes on after starting the car: 1. The vehicle fault light is usually caused by the fuel emission system. 2. When the computer receives the parameters from the oxygen sensor and the exhaust emissions seriously exceed the national legal standards. Poor combustion state: Poor engine combustion state is the main reason for the engine fault light to come on. 3. Engine knocking, usually there are three situations: (1) The car does not move. (2) The car moves, but the engine noise is too loud. (3) There is an obvious knocking sound from the cylinder. 4. Internal reasons for the engine fault light to come on: (1) Poor fuel quality. (2) The engine cylinder is not clean and has accumulated carbon deposits. 5. The computer cannot obtain engine data. 6. False fault. A fault code is reported, but the operation is normal, which may be due to an operation that exceeds the computer's control range, and the computer feedbacks a fault code.
As an enthusiast who often repairs cars myself, I have to say that a common reason for the engine warning light to come on is when the control system detects an abnormality. For example, a faulty oxygen sensor can falsely report excessive emissions, or aging spark plugs can cause a misfire. I usually turn off the engine, wait a few minutes, and restart it to see if the light remains on. If it does, I check whether the fuel cap is tightened properly—a loose cap can also trigger the alarm. Next, using an OBD scanner to read the trouble codes is a cost-effective approach, as it can identify specific issues like fuel pump or mass airflow sensor problems. Don’t forget to check for loose wiring harness connectors—corroded connections can cause signal failures. Don’t delay addressing this issue, as it could lead to increased fuel consumption or damage to the catalytic converter, resulting in higher repair costs. I recommend regular maintenance, such as checking sensors every 10,000 kilometers, to prevent minor issues from escalating into major failures.
Veteran long-distance drivers' experience tells us that if the engine warning light comes on immediately after startup, it's mostly due to sensor issues or fuel system problems. When I encountered this before and ignored it, my fuel consumption skyrocketed and black smoke appeared - it turned out to be clogged fuel injectors. Common triggers include loose fuel caps or expired spark plugs, and sometimes emission system malfunctions. When the light comes on, it's best not to continue highway driving; proceed at low speed to a repair shop for diagnostic code reading. Don't treat it lightly - delays can worsen the problem. Regular oil changes and filter inspections can help prevent such failures.
