The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2017 GLE350d AdBlue Warning & Countdown - P20EE Code

0

Mike T. · rep 0 · May 22, 4:11 AM · 1 replies · solved · Question

Vehicle: 2017 Mercedes-Benz GLE350d

Hello everyone,

I'm having a major headache with my 2017 Mercedes-Benz GLE350d (W166, OM642 engine). The AdBlue warning light came on, and now I have the dreaded 'Starts remaining' countdown on my dashboard. I've refilled the AdBlue tank, but the warning hasn't cleared, and the countdown is still ticking down.

I scanned it and got a P20EE code: 'SCR NOx Catalyst Efficiency Below Threshold (Bank 1)'. This is really frustrating, as I rely on this vehicle daily, and I don't want it to leave me stranded when the countdown hits zero.

Has anyone dealt with this specific issue on their Mercedes diesel? Is it usually the NOx sensor, the AdBlue heater, or something more serious with the SCR system? Any tips on what to check or how to potentially reset this without a dealership visit would be great.

✓ Accepted solution

ClearTheCode Admin

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

0

ClearTheCode admin answer:

The P20EE code (SCR NOx Catalyst Efficiency Below Threshold) on your 2017 Mercedes-Benz GLE350d, combined with the AdBlue warning and countdown, points to an issue with your Selective Catalytic Reduction (SCR) system, which is critical for emissions control in diesel vehicles. This system uses AdBlue (Diesel Exhaust Fluid - DEF) to reduce NOx emissions.

Here are the most common causes and diagnostic approaches:

  1. Faulty NOx Sensors:

    • Diagnosis: Mercedes-Benz vehicles typically have two NOx sensors (upstream and downstream of the SCR catalyst). A failing sensor can send incorrect readings, leading the ECU to believe the SCR system isn't working efficiently, even if it is. The P20EE often points directly to this.
    • Causes: Sensor failure due to age, heat, or contamination.

  2. AdBlue Heater or Level Sensor Failure:

    • Diagnosis: The AdBlue system requires the fluid to be at a certain temperature to function correctly. If the heater element in the AdBlue tank fails, the fluid can crystallize in cold weather, preventing proper injection. A faulty level sensor can also give false readings, even after a refill.
    • Causes: Electrical failure of the heater, mechanical failure of the level sensor.

  3. Clogged AdBlue Injector:

    • Diagnosis: The AdBlue injector sprays the DEF into the exhaust stream. If it becomes clogged with crystallized DEF, it won't spray correctly, leading to insufficient NOx reduction. This can trigger the P20EE code.
    • Causes: Crystallization of DEF, poor quality DEF, infrequent use.

  4. SCR Catalyst Degradation:

    • Diagnosis: Over time, the SCR catalyst itself can become less efficient. This is less common than sensor or injector issues but can happen, especially if the engine has been running rich or with other issues for an extended period.
    • Causes: Age, contamination, prolonged operation with system faults.

When to see a shop:

It is highly recommended to take your GLE350d to a Mercedes-Benz dealership or a specialized independent shop as soon as possible. The 'Starts remaining' countdown is a hard limit, and once it reaches zero, your vehicle will not restart. Specialized Mercedes diagnostic tools (XENTRY/DAS) are required to accurately diagnose SCR system faults, perform necessary adaptations, and clear the countdown. Attempting to force a reset without addressing the underlying issue will only lead to the problem recurring. They can perform specific tests on the NOx sensors, AdBlue heater, and injector to pinpoint the exact component causing the P20EE code and the countdown.

Menu

Help & account