What Causes Both the Snowflake Light and S Light to Illuminate in Automatic Transmission Vehicles?
3 Answers
Low outdoor temperatures and signal transmission errors can cause the snowflake light to illuminate; the S light may come on due to faults in the engine or transmission. Detailed reasons for both the snowflake light and S light illuminating in automatic transmission vehicles include: 1. Transmission fluid: If the quality of the transmission fluid is abnormal, it may damage the solenoid valve, causing both the snowflake light and S light to illuminate. 2. Pressure valve and lock-up valve: If the two pressure valves and clutch lock-up valve malfunction, or if the gear control valve fails, it can also result in both lights illuminating. 3. Outdoor temperature: The snowflake light serves as a temperature indicator—it does not illuminate above 4°C, shows a yellow snowflake light between 4°C and 0°C, and displays a red snowflake light below 0°C.
As a veteran driver with over a decade of automatic transmission experience, I've encountered several instances where both the snowflake light and S light illuminated simultaneously. The snowflake light indicates snow mode, typically activated on icy roads to limit engine torque and prevent skidding; the S light stands for sport mode, used during rapid acceleration. When both lights come on, it's likely a system malfunction—possibly a stuck or accidentally pressed button, especially in dusty or humid environments. It could also be an electrical issue, such as a short circuit or blown fuse, causing signal overlap. This confuses the transmission, leading to rough shifting or unstable power during driving, which poses significant risks. My advice is to first turn off and restart the engine a few times. If that doesn't work, head to a professional auto repair shop to check the electrical circuits.
My newly purchased automatic transmission car sometimes does this too, with both the snowflake light and the S light illuminating, which is quite annoying. The former indicates anti-slip mode, while the latter is for sport/acceleration mode. Having both on simultaneously is like they're fighting each other. Common causes include software bugs or temperature sensor false alarms, such as flashing lights erratically when detecting low temperatures during cold starts. Don't underestimate it, as this can lead to sluggish transmission response or increased fuel consumption. Based on my troubleshooting experience, try resetting the system or disconnecting the battery negative terminal for a few minutes—many modern cars can be fixed this way. If the issue persists, scan for trouble codes immediately to prevent the problem from escalating.
