What it means
The DEF consumption observed over the dosing window is above the model expectation — typically a leaking injector seat, leaking line fitting, or a pressure-control valve that vents constantly 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 for NOx control. The module compares expected use with the amount consumed over a dosing period. This code sets when consumption is higher than expected, which can result from fluid leaking into the exhaust or from a leak in the delivery system.
Common causes
Most likely first.
- Injector seat leaks DEF into exhaust
- Cracked line or fitting
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
- Review freeze-frame and live reductant-consumption data to see when use exceeded the expected amount and whether dosing was active.
- Inspect the tank, lines, fittings, and injector area for wetness, DEF crystals, or other signs of an external leak.
- Check the injector tip and seat for reductant deposits or evidence that fluid is seeping into the exhaust when dosing should stop.
- Check for related pressure-control, pump, and injector codes, and compare commanded dosing with system response using a scan tool.
- Test reductant line pressure retention and injector sealing according to the manufacturer's procedure and specification.
Common fixes
- Tighten or replace a leaking reductant line fitting.
- Replace a cracked reductant line found during inspection.
- Clean or replace a leaking injector seat or dosing injector as directed by the manufacturer's service procedure.
- Repair a pressure-control fault if testing confirms the system is venting or regulating incorrectly.
- Repair damaged wiring or connectors if testing identifies an injector-control fault.
Can I keep driving?
If there is a visible DEF leak, avoid driving until it is contained because fluid can damage nearby components and continued leakage can reduce emissions control. Otherwise, arrange repair promptly; persistent faults may trigger an emissions warning or a no-start countdown.
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.