What Causes the Engine Malfunction Light to Illuminate After Driving Through Water?

[StGabriella]

There are primarily 7 reasons why the engine malfunction light illuminates: Sensor Failure: The sensors mentioned here include coolant temperature, crankshaft position, air flow, intake air temperature, oxygen sensors, etc. When these sensors are damaged, have poor contact, or experience signal interruption, the vehicle's ECU cannot accurately obtain engine data, which triggers the engine malfunction light. Fuel or Oil Quality Issues: If fuel or engine oil is not added as required by the manufacturer, it may cause engine wear, leading to the illumination of the malfunction light. Poor Combustion of Air-Fuel Mixture: Poor combustion can result in engine carbon buildup or knocking. When detected by the oxygen sensor and reported to the ECU, the malfunction light will illuminate as a warning. Spark plug failure, ignition coil failure, fuel pump failure, or clogged fuel lines can all cause poor combustion of the air-fuel mixture in the engine. Turbocharger Issues: The intake boost pipeline or turbocharger can also cause the engine malfunction light to illuminate. The most common issue is turbocharger damage, accompanied by symptoms such as oil leakage, excessive oil consumption, reduced power, metallic noises, or blue/black smoke from the exhaust pipe. Intake Problems: If the vehicle's intake system malfunctions, it may lead to clogged engine pipelines, and in severe cases, trigger the engine malfunction light. A dirty air filter that hasn't been cleaned regularly can cause intake problems. Exhaust Problems: Exhaust system failures can also cause the engine malfunction light to illuminate. Common causes include rear oxygen sensor failure, catalytic converter issues, or faults in the exhaust camshaft and bearings. The catalytic converter is the most frequently affected component. Using leaded gasoline, lead- or silicon-based lubricant additives, physical damage to the catalytic converter, or fuel system failures can easily lead to catalytic converter problems. Anti-Theft System Malfunction: If the vehicle's electronic anti-theft system fails or if the anti-theft controller does not match the engine electronic controller, the anti-theft system can prevent the engine from operating normally, and the engine malfunction light will illuminate. If the engine malfunction light illuminates, follow these steps: First, check if the engine is running normally and whether there are issues such as shaking or smoke. If so, avoid restarting the engine. Particularly, do not restart the engine if a red warning light is illuminated. If the engine can start, turn it off for 5-10 minutes. Then, 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 enter self-test mode after powering on. Wait for 5-10 seconds and observe whether the malfunction light on the dashboard turns off. If the malfunction light remains on, visit a service station as soon as possible for diagnosis. The service station can use a portable diagnostic tool to read the fault codes, identify the issue, and perform targeted repairs.

[LaOlivia]

I've experienced the engine warning light coming on after driving through water quite a few times, mainly because water got into places it shouldn't have and messed with the electrical system. For example, when water enters sensor areas like the oxygen sensor or crankshaft position sensor, they start sending false error signals to the ECU, triggering the warning light. Another issue could be short circuits or poor grounding - high voltage current leakage during water exposure can cause interference. If water enters the intake system, the air-fuel ratio gets disrupted, making the engine run rough and the light comes on. More seriously, if water reaches spark plugs or ignition coils causing a short circuit, it instantly triggers the warning. Don't panic when this happens - find a safe place to stop and check for obvious water intrusion. After letting the engine dry, see if the light goes off. If it stays on, it's best to visit a repair shop to read the trouble codes and identify the exact problem.