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2021 GLE 350 AdBlue Warning and No-Start Countdown - P20EE

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Chris P. · rep 0 · May 22, 4:11 AM · 1 replies · solved · Question

Vehicle: 2021 Mercedes-Benz GLE 350

Hello everyone,

I'm having a major headache with my 2021 Mercedes-Benz GLE 350 (V167) diesel. I recently got an 'AdBlue Malfunction' warning on the dash, followed by a countdown to a no-start condition. It's now showing 'Starts remaining: 10'. I checked the AdBlue tank, and it's full. I also tried filling it up a bit more just in case, but the warning persists.

My OBD-II scanner is showing code P20EE - 'SCR NOx Catalyst Efficiency Below Threshold (Bank 1)'. This is really frustrating, especially with the no-start countdown. Has anyone else with a newer GLE diesel experienced this? What's the typical fix for this kind of AdBlue system issue?

Any advice on how to tackle this before I'm stranded would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:11 AM

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ClearTheCode admin answer:

The AdBlue system, also known as Selective Catalytic Reduction (SCR), is critical for emissions control in your 2021 Mercedes-Benz GLE 350 diesel. A P20EE code with a no-start countdown indicates a significant issue that needs immediate attention.

  1. Common Causes for P20EE and AdBlue Malfunction:

    • NOx Sensor Failure: This is a very common cause. The NOx sensors monitor the effectiveness of the SCR system. If a sensor fails or provides incorrect readings, the system can trigger a malfunction and the P20EE code.
    • AdBlue Heater/Pump Issues: The AdBlue fluid can crystallize in cold temperatures. The system has heaters and a pump to ensure proper flow. A failure in either of these components can prevent AdBlue from being injected correctly, leading to the P20EE code.
    • Clogged AdBlue Injector: The injector that sprays AdBlue into the exhaust stream can become clogged with crystallized urea, preventing proper operation.
    • SCR Catalyst Degradation: While less common on newer vehicles, the SCR catalyst itself can degrade over time, reducing its efficiency below the required threshold.
    • Wiring/Electrical Issues: Damaged wiring or connectors to any of the AdBlue system components can also cause these faults.
    • Software Glitches: Occasionally, a software update for the engine control unit (ECU) or SCR module can resolve erroneous warnings.

  2. When to See a Shop:

    • Given the no-start countdown, this is a critical issue that requires professional diagnosis immediately. Once the countdown reaches zero, your vehicle will not start.
    • A Mercedes-Benz dealership or a specialized independent shop with XENTRY/DAS diagnostic equipment is essential. They can accurately read specific fault codes within the SCR module, perform guided tests, and identify the exact component failure.
    • Attempting to clear the code with a generic scanner will likely not resolve the underlying issue and the countdown will continue. Do not delay in getting this serviced.
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