What Causes the S and Snowflake Lights to Flash on the 408 Transmission Fault Dashboard?
3 Answers
Here are the specific reasons for the S and snowflake lights flashing on the 408 transmission dashboard: 1. Low outdoor temperature. When driving in an environment where the outdoor temperature is below 4 degrees Celsius, the outdoor temperature sensor measures the temperature and transmits it to the control system via wiring. The control system then relays this information to the dashboard, causing the snowflake light to illuminate as a warning to the driver to drive cautiously. This alerts the driver to potential hazards such as standing water, ice, or frost due to low temperatures and prompts them to prepare for driving in cold conditions. Typically, the snowflake light appears yellow between 0-4 degrees Celsius and red below 0 degrees Celsius. This is an indicator light and does not affect the vehicle's normal operation. 2. If the outdoor temperature sensor is faulty, it may transmit incorrect temperature readings to the control system and dashboard. Whether the readings are higher or lower than the actual temperature, the snowflake light will illuminate, indicating a malfunction. 3. If there is an issue with the vehicle's wiring or control system, the outdoor temperature sensor may correctly measure the temperature, but errors in transmission or feedback can cause the dashboard to display an incorrect temperature. In this case, the snowflake light will also illuminate, signaling a fault.
When you see the S and snowflake lights flashing on the 408 dashboard, I must remind you that this usually indicates a transmission warning about internal issues. The S light on Peugeot vehicles often signals a failure in sport mode or the activation of a fault mode, while the flashing snowflake light is typically triggered by low temperatures or an overheated transmission. The causes vary widely, but the most common ones include insufficient or contaminated transmission fluid—dirty or thinning fluid can impair lubrication and lead to overheating. Another possibility is a malfunction in the transmission control module, such as faulty sensor readings or stuck solenoids, which may trick the system into falsely detecting a low-temperature state as a danger alert. Other factors could involve electrical shorts, relay failures, or software bugs. In such cases, I recommend safely parking the vehicle first and checking the dipstick for proper fluid level and color. If the fluid is low, try topping it up; if that doesn’t help, scan for OBD codes to pinpoint the issue. Don’t ignore it—continuing to drive could damage the entire transmission, so prompt professional servicing is the wisest approach. Regular fluid changes and inspections can help prevent similar troubles in the future.
I often hear friends complain about this phenomenon while driving. Here are the common reasons summarized: the S light flashing indicates a transmission issue, such as entering a protection mode that limits functions. The snowflake light is often related to temperature problems, like incorrect sensor detection of a cold environment or overheating inside the transmission. Possible root causes include aging transmission oil reducing performance, insufficient oil leading to poor heat dissipation, or faults in the electronic control unit triggering incorrect signals. For a simple check: after the car cools down, open the hood, locate the automatic transmission dipstick to confirm the oil level is within the normal range, and ensure the oil is clear without impurities. If everything seems fine, check the fuses or wiring connections. In daily driving, avoid sudden acceleration to reduce transmission stress, which can extend the lifespan of components. If a problem is detected, don't continue driving recklessly to avoid worsening the damage. It's best to find a roadside shop to scan the codes for diagnosis.
