Practice question

What will happen if a modern heavy-duty truck runs completely out of Diesel Exhaust Fluid (DEF) while driving?

  1. The engine will instantly lock up and stop running
  2. The engine will enter a derate mode, significantly reducing power and limiting speed until DEF is added
  3. The truck will switch to running on battery power automatically
  4. The exhaust system will bypass the SCR catalytic converter and operate normally

Answer: B — The engine will enter a derate mode, significantly reducing power and limiting speed until DEF is added

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