What Causes the Malfunction Light to Illuminate on Rainy Days?
3 Answers
Generally, there are several main reasons that can cause the engine malfunction light to illuminate. 1. Sensor issues: 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 will then trigger the engine malfunction light. 2. Maintenance issues: Poor engine maintenance is the most common cause of the engine malfunction light illuminating. Vehicles have specific maintenance cycles, and if the owner does not adhere to the maintenance schedule and has poor driving habits, it will increase the burden on the engine's operation. 3. Fuel quality issues: The fuel quality here includes both fuel and engine oil. The fuel added to a car usually has a specific grade, and engine oil can be semi-synthetic or fully synthetic. Manufacturers generally recommend which grade of fuel and type of engine oil owners should use. If the owner does not follow these recommendations, it can lead to engine wear over time.
My SUV's warning lights always come on when it rains, especially the ABS and engine lights which are most noticeable. It's probably because rainwater seeps into the chassis or engine compartment, wetting the sensors. For example, wheel speed sensors located low are prone to water accumulation and moisture, causing signal errors. Water entering circuit connectors causing short circuits or poor grounding can also trigger false alarms, leading the computer to misdiagnose faults. I suggest checking immediately after rain to ensure wiring harnesses are dry and properly sealed, parking away from puddles, and slowing down to pull over when lights come on to avoid pushing through and risking accidents. Modified cars with additional wiring that isn't waterproof are more prone to issues and should have protective covers added. If the lights turn off when the weather clears, repairs may not be necessary, but if they stay on, it's best to have a professional shop diagnose the problem to prevent minor issues from turning into major accidents.
The most common cause of warning lights turning on during rainy days is moisture affecting the sensors or short circuits in the wiring, or dirty rain sensors leading to inaccurate signals. Frequent activation and flashing of the ABS system light on slippery surfaces is normal, but continuous illumination requires caution as it may indicate water ingress in wire harness connectors or ground failure. Older vehicles with aged wiring are at higher risk of rainwater leakage, causing voltage fluctuations and light activation. It is recommended to check that the engine compartment drainage channels are not blocked and to replace sealing compounds regularly. If the light comes on, stay calm, ensure safe parking, and wait for conditions to dry before assessing further; if the light remains on for an extended period, test the battery voltage and perform ECU diagnostics to prevent potential failures.
