What it means
The DEF consumption observed over the dosing window is below the model expectation — typically a clogged dosing nozzle, weak pump, or leak between pump and injector that recirculates DEF back to the tank.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The reductant system meters DEF or AdBlue into the exhaust to support NOx reduction. The module compares expected reductant use with consumption observed over a dosing period. This code sets when measured consumption is too low, which can indicate that insufficient fluid reaches the exhaust.
Common causes
Most likely first.
- Dosing nozzle clogged with crystallised DEF
- Pump weak — flow under target
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Read freeze-frame data and live reductant-consumption and dosing values to confirm when consumption fell below the model's expectation.
- Check the DEF or AdBlue level and inspect the tank area, lines, and injector for obvious leaks, damage, or crystallised deposits.
- Inspect the dosing nozzle for crystallised reductant that could block flow, following the manufacturer's service guidance.
- Check for related pump, pressure, heater, and dosing-injector codes, then test commanded dosing response with a suitable scan tool.
- Measure reductant delivery and pump output using the manufacturer's procedure and specification to distinguish a weak pump from a blocked injector or line.
Common fixes
- Clean or replace a dosing nozzle blocked by crystallised DEF, as appropriate for the manufacturer's service guidance.
- Repair a leaking or damaged reductant line or connection found during inspection.
- Repair wiring or a connector fault affecting the reductant pump or injector.
- Replace a pump confirmed to deliver below the manufacturer's specification.
- Replace a faulty dosing injector if testing confirms it fails to deliver the commanded amount.
Can I keep driving?
You can usually drive temporarily if the vehicle runs normally, but avoid ignoring the warning because some vehicles start a no-start countdown when reductant faults persist. Arrange repair promptly and follow any displayed countdown or power restriction.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.