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AdBlue Warning & Countdown on 2017 GLE350d - P20EE Code

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Kevin B. · rep 0 · May 22, 4:12 AM · 1 replies · solved · Question

Vehicle: 2017 Mercedes-Benz GLE350d

Hi everyone,

I'm having a major headache with my 2017 Mercedes-Benz GLE350d (W166). I recently got an 'AdBlue Malfunction' warning on the dash, followed by a countdown message saying 'Starts remaining: 800 miles'. I topped up the AdBlue tank, but the message hasn't gone away.

I scanned it with my OBD-II reader and it's showing code P20EE - 'SCR NOx Catalyst Efficiency Below Threshold (Bank 1)'. I'm really worried about the countdown, as I know these cars can become undriveable once it hits zero.

Has anyone dealt with this specific issue on their diesel Mercedes? What was the fix? Is it usually a sensor, the heater, or something more serious with the SCR system? Any insights would be super helpful!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:12 AM

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ClearTheCode admin answer:

The AdBlue warning and P20EE code on your 2017 Mercedes-Benz GLE350d indicate a problem with the Selective Catalytic Reduction (SCR) system, specifically related to its efficiency in reducing NOx emissions. The countdown is a critical feature designed to ensure compliance with emissions regulations, and the vehicle will indeed prevent starting once it reaches zero.

Common Causes for AdBlue Malfunction and P20EE:

  1. NOx Sensors: These sensors monitor the NOx levels before and after the SCR catalyst. A faulty sensor (either upstream or downstream) can trigger this code.
  2. AdBlue Injector (Doser Valve): If the injector is clogged or malfunctioning, it won't spray the correct amount of AdBlue into the exhaust, leading to inefficient NOx reduction.
  3. AdBlue Heater/Pump: The AdBlue fluid can crystallize in cold temperatures. The heater ensures it remains liquid, and the pump delivers it to the injector. Failures in these components can prevent proper AdBlue delivery.
  4. SCR Catalyst Degradation: Over time, the catalyst itself can become less efficient, though this is less common in newer vehicles.
  5. Contaminated AdBlue: Using incorrect or contaminated AdBlue fluid can damage the system.
  6. Software Issues: Sometimes, a software update or reset is needed after an AdBlue refill.

Troubleshooting Steps (Limited):

  1. Ensure Proper Refill: Double-check that you used the correct AdBlue fluid and filled the tank completely.
  2. Check for Leaks: Visually inspect the AdBlue lines and tank for any leaks.

When to See a Shop:

Given the complexity of the SCR system and the impending no-start condition, it is highly recommended to take your GLE350d to a Mercedes-Benz dealership or a specialist shop immediately. They have the advanced diagnostic tools to:

  • Read specific fault codes related to the SCR system.
  • Test the functionality of the NOx sensors, AdBlue injector, pump, and heater.
  • Perform guided diagnostics to pinpoint the exact component failure.
  • Clear the AdBlue countdown after the repair is completed.

Attempting to ignore this issue or perform DIY repairs without proper knowledge can lead to further complications and potentially leave you stranded.

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