Is the DEF Additive Supply Line Mercedes BlueTEC covered under the extended warranty?

The Mercedes BlueTec Settlement gave cars and extended warranty on most of the emissions and fueling system, including the diesel exhaust fluid (DEF) or additive system…

What does the DEF Additive Supply Line Do?

The DEF Additive Supply Line connects the additive pump (aka sending unit) – which is typically located in the DEF tank to – to the DEF injector which is attached to the exhaust system before the NOx catalyst.

What is covered under the Mercedes BlueTEC Extended Emissions Warranty?

This varies slightly by vehicle, but largely the following components are covered:

  • Diesel Oxidation Catalyst (DOC)
  • Diesel Particulate Filter (DPF)
  • Selective Catalytic Reduction (SCR) Catalyst
  • Diesel Exhaust Fluid (DEF) Injector
  • Diesel Exhaust Fluid (DEF) Injector Controller
  • Diesel Exhaust Fluid (DEF) Supply Module
  • Diesel Exhaust Fluid (DEF) Pump

Is the DEF Additive Supply Line Mercedes BlueTEC covered under the extended warranty?

While the vast majority of other DEF components are covered, the supply line was left out of the emissions coverage.

How do you replace the DEF Additive Supply Line on Mercedes BlueTEC and Sprinter models?

Luckily the supply line is not complicated or difficult to install. You can purchase the supply line online easily ( – Diesel Emissions Fluid (DEF) Injector Supply Lines). These lines plug in using quick connectors on either end. Some models include built-in heaters, too. Since these are model specific, be sure to buy the correct version – doing a VIN check never hurts! Finally, since these lines travel across the bottom of the car, a shop lift will make the job much easier – though a good set of jack stands will do.

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