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If your Mercedes C-Class throws an
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AdBlue or check AdBlue system warning
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and the engine light comes on, don't
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panic. First thing to do is check the
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AdBlue level and refill with the right
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fluid. AdBlue or DF, not water or
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additives. On most C-Class models, the
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AdBlue filler is under the fuel flap, so
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pop the flap and top it up using a
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canister or pump. If the level was low,
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topping up will often clear the warning
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once the system rereads the level. If
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you refilled and the light stays on,
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there's a simple in-car trick you can
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try next. Turn the ignition on but don't
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start the engine. Acknowledge the
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message with the okay button on the
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steering wheel and navigate the
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instrument cluster menu to the vehicle
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or service settings. Many Mercedes let
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you request an add blue or SCR reset
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from that hidden menu. Press through the
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prompts and confirm. That often forces
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the system to recheck the tank level and
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clear the warning if no fault remains.
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If the light still won't go away, it's
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time for a diagnostic reset with a
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proper Mercedes tool. Dealers use Xentry
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guided control to run an STR reset or
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clear adaptions. And aftermarket
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scanners like Launch or Autel can do the
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same if they support Mercedes STR
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functions. Run the guided reset. Check
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for stored fault codes in the ECU module
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and follow the tools recommendations. If
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you see persistent codes for the
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metering valve, injector, or level
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sensor, those parts may need cleaning,
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replacement, or a teach-in procedure.
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Quick safety and reality check. Some
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people try software bypasses, or dubious
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shortcuts. Don't. Clearing a warning
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without fixing the root cause can get
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you stranded or fail emissions checks.
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Common real causes include a faulty
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level sensor, blocked injector or SCR
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catalyst, or software needing a guided
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reset. So, if the diagnostic shows
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those, fix the part and then perform the
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reset. Wrap up on camera by saying
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exactly what you did. You checked the
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tank, topped up with genuine AdBlue,
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tried the cluster reset, and then used a
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scanner if needed. Tell viewers that if
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they're not comfortable doing the
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diagnostic or replacing parts, a dealer
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or an independent diesel specialist can
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sort the SCR system and perform the X
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entry or equivalent reset safely.
