OBD-II Code
P204F
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$180–$2,400
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P204F means the reductant (DEF/AdBlue) injection system as a whole is failing its performance rationality check - the ECM expects a certain DEF dosing volume per mile based on NOx upstream readings, fuel consumed, and exhaust temperature, and the actual dosed volume is outside that window.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP204F means the reductant (DEF/AdBlue) injection system as a whole is failing its performance rationality check - the ECM expects a certain DEF dosin…
P204F means the reductant (DEF/AdBlue) injection system as a whole is failing its performance rationality check - the ECM expects a certain DEF dosing volume per mile based on NOx upstream readings, fuel consumed, and exhaust temperature, and the actual dosed volume is outside that window.
Cheapest-first ladder
- pull DEF tank level, DEF tank temperature, dosing line pressure (typical 5 to 9 bar when active), and commanded versus actual dosing rate (most systems target 2 to 6 percent of fuel rate by volume); a frozen DEF line, a clogged dosing injector, or a failed transfer pump all show here.
- Caveat: DEF system fault codes have ramp-down mileage countdowns to 5 mph speed limit on most platforms, so always check the inducement state before sending the truck back to the customer.
Vehicle-specific patterns2011 to 2014 Ford 6.7L Powerstroke notoriously fail the DEF heater plus level sender combo unit, Ford TSB 14-0021 and recall 14E04; 2010 to 2016 Merc…
- 2011to 2014 Ford 6.7L Powerstroke notoriously fail the DEF heater plus level sender combo unit, Ford TSB 14-0021 and recall 14E04;
- 2010to 2016 Mercedes Sprinter OM642/OM651 BlueTEC fail the DEF supply pump after DEF crystallization;
- 2007to 2010 Dodge Ram 6.7L Cummins set P204F from a clogged dosing injector cleanable with off-vehicle ultrasonic;
- 2011to 2016 Duramax LML throw the code from the well-known DEF heater failure, GM safety recall 14V-252.
Estimated repair$180 to $2,400.
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