What Causes the Engine Fault Indicator to Illuminate Yellow?

[DeOlivia]

Reasons for the engine fault indicator illuminating yellow: 1. Poor quality gasoline that fails to meet standards, leading to incomplete combustion of the air-fuel mixture during engine operation, causing the engine fault light to illuminate; 2. Damage to the oxygen sensor or a faulty/loose sensor connector can result in a mixture that is too lean or too rich, triggering the fault light; 3. Malfunction of the air flow sensor or its wiring prevents the ECU from receiving accurate intake air volume signals, disrupting normal fuel quantity control. This can cause the mixture to be too lean or too rich, preventing the engine from operating properly. Although a faulty air flow sensor may not prevent the engine from starting, symptoms such as unstable idle, poor acceleration, backfiring in the intake manifold, and black smoke from the exhaust pipe may still occur.