Consumption of DEF Fluid
This code indicates an issue with the consumption of Diesel Exhaust Fluid (DEF).
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The engine computer expects a certain amount of DEF to be injected for proper emissions control. If it's using too little or too much, the system registers a fault. This can lead to increased emissions and potential engine derating.
What the computer is actually seeing
The Electronic Control Unit (ECU) monitors the quantity of DEF being used compared to the amount expected based on engine operation, fuel rates, and exhaust temperatures.
What a healthy reading looks like
DEF consumption should be proportional to fuel consumption; typical rates are about 3-5% of diesel fuel usage. If the DEF consumption deviates significantly, like less than 1% or more than 7%, this code may trigger.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check DEF quality. Use certified DEF only. Low quality can cause issues. If dirty or diluted, replace.
- 22. Inspect DEF lines and connections for leaks. Look for crystallization or any signs of fluid escape. Fix any leaks found.
- 33. Measure the actual DEF consumption versus fuel consumption. If it's outside the expected 3-5%, proceed to the next step.
- 44. Test the DEF injector operation. Use a scan tool to command the injector on and verify operation under controlled conditions.
- 55. Check the voltage and ground at the DEF pump and injector. Expect around 12V when active. If no voltage, check for wiring issues.
- 66. Replace any faulty components found in the previous steps. If all checks are good and the code persists, consider reprogramming the ECU or checking for software updates.
Common causes
- Faulty DEF injector
- DEF quality issues (contaminated or diluted DEF)
- Faulty DEF pump
- Leaking DEF lines or fittings
- Plugged or damaged DEF injector nozzle
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable but expect reduced performance and increased emissions. Fix it soon to avoid further issues.
Will this code come back after clearing?
If the underlying issue isn't resolved, yes, it will likely return.
Why does this code appear with other codes?
They often indicate related issues with the DEF or emissions systems, which work together.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →