During a multi-day cold snap where temperatures hover around -20°C, the DEF system on a wheel loader repeatedly indicates low DEF levels despite being recently filled. No leaks are visible. What is the most plausible technical explanation for this persistent indication?

Question: During a multi-day cold snap where temperatures hover around -20°C, the DEF system on a wheel loader repeatedly indicates low DEF levels despite being recently filled. No leaks are visible. What is the most plausible technical explanation for this persistent indication?

Answer options: ✅ The DEF tank level sensor is malfunctioning due to ice crystals interfering with its operation and providing inaccurate readings.

• The DEF fluid is chemically degrading faster in the cold, leading to its rapid consumption for regeneration.
• A software glitch in the machine's ECU is misinterpreting the DEF signal in extreme cold conditions.
• The DEF fluid is expanding in the cold, causing the sensor to misread in a counter-intuitive manner.

Correct answer: The DEF tank level sensor is malfunctioning due to ice crystals interfering with its operation and providing inaccurate readings.

Explanation: In extreme cold, DEF can form ice slush or partial freezing within the tank, interfering with the float or ultrasonic level sensors, causing inaccurate 'low level' readings even when the tank contains sufficient, albeit partially frozen, fluid.