What Causes the Engine Fault Light to Illuminate in a New Car While It Can Still Run Normally?

[LeIsaac]

When the engine fault light comes on, it may serve as a warning indicating that certain system parameters in the vehicle might have exceeded the set range. In such cases, the vehicle can usually continue to operate, and the light is typically yellow. There is also a more severe situation where the light turns red, signaling a very serious fault. Although the vehicle might still be drivable, it is crucial to stop immediately, turn off the engine, and refrain from further driving for safety reasons, followed by a thorough inspection to identify the fault. The engine fault light may illuminate due to the following seven main reasons: Sensor Malfunction: Sensors such as those for coolant temperature, crankshaft position, air flow, intake air temperature, and oxygen sensors may become damaged, have poor connections, or experience signal interruptions. When the vehicle's ECU cannot accurately obtain engine data due to these issues, the engine fault light will illuminate. Fuel or Oil Quality Issues: Failure to use the fuel or oil as specified by the manufacturer may lead to engine wear, triggering the fault light. Poor Combustion of Air-Fuel Mixture: Incomplete combustion can cause engine carbon buildup or knocking. Once detected by the oxygen sensor and reported to the ECU, the fault light will illuminate as a warning. Issues such as faulty spark plugs, ignition coils, fuel pumps, or clogged fuel lines can lead to poor combustion. Turbocharger Problems: Issues with the intake boost system or turbocharger can also cause the engine fault light to come on. The most common problem is a damaged turbocharger, often accompanied by symptoms like oil leaks, excessive oil consumption, reduced power, metallic noises, or blue/black smoke from the exhaust. Intake Issues: Problems with the vehicle's air intake system may lead to clogged engine passages, and in severe cases, trigger the engine fault light. A dirty or uncleaned air filter can cause intake problems. Exhaust System Issues: Faults in the exhaust system, such as problems with the rear oxygen sensor, catalytic converter, exhaust camshaft, or bearings, can also cause the engine fault light to illuminate. The catalytic converter is the most common culprit, often affected by the use of leaded gasoline, lead- or silicon-based lubricant additives, physical damage, or fuel system malfunctions. Anti-Theft System Fault: If the vehicle's electronic anti-theft system malfunctions or if there is a mismatch between the anti-theft controller and the engine control unit, the engine may fail to operate correctly, and the fault light will illuminate. If the engine fault light comes on, follow these steps: First, check whether the engine is running normally and if there are any issues like shaking or smoke. If such problems exist, avoid restarting the engine. Notably, if the light is red, do not attempt to restart the engine under any circumstances. If the engine can be started, turn it off and wait for 5-10 minutes. Without pressing the brake, press the start button once or turn the key halfway to the 'ON' position (without depressing the clutch). The vehicle will perform a self-check upon powering up. Observe whether the fault light turns off after 5-10 seconds. If the light remains on, visit a service center as soon as possible. Technicians can use a portable diagnostic tool to read the fault codes, identify the issue, and perform targeted repairs.

[LeCole]

I just got my new car less than a month ago and drove a few thousand kilometers when suddenly the engine malfunction light came on. The car seems perfectly normal, with no issues in acceleration or turning, which puzzles me. I remember last time when I washed the car, the fuel tank cap wasn’t tightened properly, and fuel vapor leakage might have triggered the light. It could also be a false alarm from the oxygen sensor—new car sensors are often too sensitive and prone to minor issues. Or perhaps there’s a tiny leak in the exhaust system, but it doesn’t affect driving. A friend who works at a 4S店 told me that new cars often have software bugs, and the ECU module might misjudge. For peace of mind, I spent some time scanning the trouble codes, and the results showed no major issues. Regular maintenance in the future can help prevent such problems. Never ignore small issues, as they might turn into big ones.