A wheel loader's instrument panel includes a DEF (Diesel Exhaust Fluid) level gauge. What is the consequence of allowing the DEF tank to run critically low or empty?

Question: A wheel loader's instrument panel includes a DEF (Diesel Exhaust Fluid) level gauge. What is the consequence of allowing the DEF tank to run critically low or empty?

Answer options:

• The engine will immediately shut down to prevent damage.
• The machine will continue to operate normally, but with reduced fuel efficiency. ✅ The engine's power output will be derated, and it may eventually become inoperable.
• The hydraulic system will lose pressure, affecting bucket performance.

Correct answer: The engine's power output will be derated, and it may eventually become inoperable.

Explanation: Modern diesel engines with Selective Catalytic Reduction (SCR) systems require DEF to meet emissions standards. If the DEF level becomes critically low or empty, the engine's onboard diagnostic system will progressively derate engine power, and eventually prevent operation until DEF is replenished, in accordance with emissions regulations. Reference manufacturer's operation manuals and emissions requirements.