What Causes the Yellow Engine Light in Audi A4?

[CharlotteDella]

Audi A4's yellow engine light primarily indicates an engine malfunction. Below are the reasons for engine malfunction: 1. Poor Combustion Condition: Poor combustion condition is the main reason for the engine warning light to illuminate. In automotive design, to ensure the engine operates in good condition and maintains its normal service life, oxygen sensors are installed on the engine to monitor its combustion status. 2. Poor Fuel Quality: This usually occurs when low-quality gasoline is filled at non-standard gas stations, leading to incomplete combustion of the air-fuel mixture during engine operation, which triggers the engine warning light. 3. Engine Carbon Deposits: Over time, carbon deposits accumulate inside the engine. These deposits can alter the engine's design parameters and are inherently unstable, storing heat. The stored heat can cause erratic ignition in the engine, leading to engine knocking. In such cases, the engine warning light will also illuminate.