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Fault code P204F means SCR system performance out of specification. The NOx reduction system does not reach the expected efficiency: the problem may be in the dosing or in the measurement.

Typical symptoms

• AdBlue message on the display
• Limited remaining starts
• Reduced power
• Abnormal additive consumption

Most common causes

• Failed downstream NOx sensor (a very frequent cause)
• Degraded SCR catalyst
• Insufficient dosing due to a partially blocked injector
• Non-compliant AdBlue
• Exhaust leaks between the sensors

How it is checked in diagnosis

• Reading the values of the two NOx sensors
• Checking actual dosing against requested
• Exhaust leak check
• Additive quality test

Can you drive with code P204F?

Yes, until the permitted starts run out.

How MasterTuning helps

We read the real values from the ECU, not just the code: that is the difference between identifying the component responsible and replacing parts by trial and error. After the repair we clear the fault and check that it does not come back. Centres throughout Italy.

Read more: vehicle database · what is ECU remapping · find an installer

Do you have code P204F on your car? Book a diagnosis at your nearest MasterTuning centre.

Frequently asked questions

What does fault code P204F mean?

Code P204F means SCR system performance out of specification. The NOx reduction system does not reach the expected efficiency: the problem may be in the dosing or in the measurement.

Can you drive with fault P204F?

Yes, until the permitted starts run out.

Is clearing code P204F enough to fix it?

No: if the cause is still present the code comes back after a few kilometres. Clearing should only be done after the repair, with the diagnostic tool.

How much does it cost to fix code P204F?

It depends on the component responsible: the diagnosis is precisely what identifies it with real measurements, avoiding unnecessary replacements that cost far more than the correct repair.