Mercedes P20F500 – AdBlue Consumption Too High

System: Emissions System (SCR) Component: AdBlue / SCR System)

Typical Symptoms

• Engine warning light illuminated
• AdBlue warning messages
• Increased AdBlue consumption
• Possible SCR system faults

Fault Codes

• P20F500 – AdBlue consumption too high

Possible Cause

• NOx sensor fault
• AdBlue injector issue
• SCR system inefficiency
• incorrect AdBlue dosing
• sensor or system control fault

Component Location

The SCR system components are located across the vehicle, including:

• AdBlue tank and pump
• AdBlue injector (exhaust system)
• NOx sensors
• SCR catalytic converter

Diagnostic Insight

This fault indicates that the system has detected higher than expected AdBlue consumption.

However, this fault code does not directly identify the root cause.

Multiple components within the SCR system can affect AdBlue consumption, making this a diagnostic-based fault.

Technicians usually carry out:

• live data analysis of AdBlue dosing
• NOx sensor readings
• system efficiency checks
• fault code correlation

With this fault alone, it is often not possible to determine the exact cause without further testing.

It is important to confirm the root cause before replacing components.
See Mercedes Fault Diagnosis Guide →

Important Note

This type of fault requires detailed diagnostic testing using specialist equipment (e.g. Mercedes Xentry). Replacing parts without proper testing may not resolve the issue.

⚠ Professional Diagnostic Recommended

SCR system faults require specialist diagnostic equipment and live data analysis. The vehicle should be inspected by a Mercedes-Benz dealer or qualified Mercedes specialist.