Fault Code P20E8: Understanding and Addressing Low AdBlue Pressure
On modern diesel vehicles equipped with SCR (Selective Catalytic Reduction) technology, fault code P20E8 – Low AdBlue Pressure – has become a common warning in workshops. This message, often accompanied by a check engine light, always raises the same question: why can’t the urea injection system maintain the required pressure?
A Revealing Symptom
The SCR system relies on injecting AdBlue at a specific pressure into the exhaust stream to reduce nitrogen oxide emissions.
When the pressure drops below expected values, the ECU registers fault code P20E8. This code can lead to very concrete consequences: degraded engine mode, dashboard warnings, or even a countdown to vehicle immobilisation.
Multiple underlying causes
Low pressure may stem from various malfunctions, such as:
- Mechanical wear,
- Electronic faults,
- Crystallisation inside the circuit,
- Improper tank filling,
- Or even questionable AdBlue quality.
Given the wide range of potential issues, outright replacement of the AdBlue module isn’t always the most suitable solution.
A Thoughtful Diagnostic Approach
Rather than opting for the fastest-but often costliest-solution, some faults can be handled more precisely by choosing electronic repair. Targeted intervention on the actual defective components often helps avoid complete module replacement.
It’s also a more sustainable way to approach automotive repair, both economically and environmentally.
Smart preventive practices
Certain habits can help maintain proper SCR system operation.
- A low fluid level in the AdBlue tank, for example, encourages air intake and crystallisation within the system.
- As for the AdBlue itself, its quality is crucial: using certified fluid reduces the risk of premature damage.
Have questions? Find your answers here!
What does fault code P20E8 mean?
It indicates that the pressure in the AdBlue injection circuit is too low, preventing the SCR anti-pollution system from functioning correctly.
Can the vehicle still drive with this fault?
In some cases, the engine enters limp mode with reduced power. If the issue persists, a mileage countdown may prevent engine start.
Does the AdBlue module always need replacing?
Not necessarily. Several components could be involved. A detailed diagnosis may allow for targeted repairs instead of full replacement.
Is this type of fault common?
Yes. With more vehicles now equipped with SCR systems, workshops are seeing this fault more and more frequently.
How can this fault be prevented?
Avoid driving with a nearly empty AdBlue tank, use only compliant AdBlue, and keep the vehicle regularly maintained.