What are the reasons for the engine malfunction indicator light (MIL) illuminating in a new JAC Junling truck?
2 Answers
The engine malfunction indicator light (MIL) may illuminate due to the following 7 main reasons: Sensor malfunction: This includes sensors such as coolant temperature, crankshaft position, mass air flow, intake air temperature, and oxygen sensors. When these sensors are damaged, have poor connections, or experience signal interruptions, the vehicle's ECU cannot accurately obtain engine data, triggering the MIL. Fuel/oil quality issues: Failure to use fuel and engine oil as specified by the manufacturer may cause engine wear, leading to MIL activation. Poor fuel mixture combustion: Incomplete combustion can cause engine carbon buildup or knocking. When detected by oxygen sensors and reported to the ECU, the MIL will illuminate as a warning. This can be caused by faulty spark plugs, ignition coils, fuel pumps, or clogged fuel lines. Turbocharger issues: Problems with the intake boost system or turbocharger can trigger the MIL. The most common issue is turbocharger damage, often accompanied by symptoms like oil leaks, excessive oil consumption, reduced power, metallic noises, or blue/black exhaust smoke. Intake system problems: Air intake issues may lead to engine passage blockage, potentially causing the MIL to illuminate. A dirty air filter that hasn't been regularly cleaned can cause intake problems. Exhaust system faults: Exhaust issues can also trigger the MIL. Common causes include rear oxygen sensor failure, catalytic converter problems (most frequent), or exhaust camshaft/bearing failures. Using leaded gasoline, lead/silicon-containing lubricant additives, physical damage to the catalytic converter, or fuel system malfunctions can all contribute to catalytic converter failure. Anti-theft system malfunction: If the vehicle's electronic anti-theft system fails or if there's incompatibility between the anti-theft controller and engine ECU, the system may prevent normal engine operation while illuminating the MIL. When the MIL illuminates, follow these steps: First, check if the engine is operating normally. If there's noticeable shaking, black smoke emission, or other abnormalities, avoid restarting the engine. Particularly important: never restart if the red warning light is on. If the engine can start, turn it off for 5-10 minutes. Then, without pressing the brake pedal, press the start button once or turn the key halfway to the ON position (without depressing the clutch). The vehicle will initiate a self-check upon power-up. After 5-10 seconds, observe whether the MIL turns off. If the light remains on, visit a service center promptly. Technicians can use diagnostic tools to read trouble codes, identify specific issues, and perform targeted repairs.
The new car's engine warning light came on, and I've seen it multiple times. The light started flashing right after I got the car—it might just be a minor misunderstanding. The most common issue is a faulty sensor, like the oxygen sensor being overly sensitive and triggering an alarm at the slightest sign of abnormal exhaust emissions. It could also be due to a dirty fuel system or new parts not yet properly broken in. Sometimes, delayed software updates cause the car's control module to misdiagnose a fault. Don't panic; try turning the engine off and restarting it a few times first. When I took it to the 4S shop for inspection, they said it's normal during the break-in period for new cars. However, if the light stays on continuously, avoid driving at high speeds and have a professional check it immediately—don't tinker with it yourself to prevent engine damage. As a side note, during the first maintenance, get a full electrical system check to prevent similar issues.
