Fault-Code Library · AdBlue / SCR
P204F: Reductant system performance
The reductant system is not meeting the performance expected by the emissions controller.
Common symptoms
- •AdBlue warning
- •Restart countdown
- •Engine light
- •Emissions readiness failure
Likely causes
- •AdBlue pump or pressure fault
- •Dosing injector problem
- •NOx sensor issue
- •Incorrect fluid or tank heater fault
First checks
- •Scan SCR subcodes and freeze-frame
- •Check reductant pressure and dosing command
- •Verify fluid quality and NOx sensor data
Important
A generic P204F should be diagnosed with manufacturer data before replacing the tank or sensors.
A fault code identifies a detected condition, not a failed part. Confirm manufacturer-specific subcodes and live data.
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