Why is the engine malfunction indicator light constantly on?
2 Answers
The engine malfunction light may illuminate due to the following six reasons: 1. Engine issues: It could be a sporadic fault, causing only the engine light to activate without triggering the fail-safe mode. Restarting the engine might make the light turn off automatically. 2. Exhaust system: An exhaust pipe leak can trigger the light when the rear oxygen sensor detects abnormal air-fuel mixture, though driving remains unaffected. 3. Fuel quality: Poor-quality fuel may activate the light without noticeable driving impact. 4. Catalytic converter: A weakened converter may trigger the light but typically doesn’t hinder performance. 5. Engine misfire: This significantly affects driving by causing improper air-fuel mixture, detected by sensors that activate the light. 6. Sensor wiring: Rodent damage to wiring (e.g., knock sensor) may illuminate the light without obvious driving issues.
I've been driving for over a decade and have encountered the check engine light staying on quite often. The most common issue is a faulty oxygen sensor, which monitors exhaust gas levels near the exhaust pipe. Aging or excessive dirt buildup can trigger the light and also increase fuel consumption. Short circuits in ignition coils or worn spark plugs are also frequent causes, leading to incomplete engine combustion. More serious problems include clogged catalytic converters, often accompanied by unusual noises and reduced power. Don't underestimate this warning light—it indicates the ECU (Engine Control Unit) has detected a fault. Continuing to drive could damage core engine components and increase repair costs. For safety, first use an OBD II scanner to read the trouble codes and identify the problem scope. If you don't have the tools, visit a professional auto repair shop for a comprehensive inspection. Regularly change engine oil and air filters to prevent sensor clogging and reduce such risks, saving money and ensuring peace of mind.
