AdBlue / Diesel Exhaust Fluid (DEF) Warning
Caution — Service soon
What It Means
The diesel exhaust fluid (AdBlue/DEF) is low. This is used in Selective Catalytic Reduction (SCR) systems to reduce NOx emissions. Running completely out may prevent the engine from starting (anti-tamper regulation).
Common Causes
- DEF/AdBlue tank needs refilling
- Faulty DEF level sensor
- DEF quality issue (contaminated or incorrect fluid)
- SCR catalyst fault
Can I Still Drive?
Yes — but refill the DEF tank at your earliest convenience. Most vehicles have multiple warning stages: first warning (refill soon), second warning (refill now), third warning (engine will not restart after shutdown). Do not put diesel fuel in the DEF tank.
Estimated Repair Cost
$10 – $50
This is an estimate only. Actual costs vary by vehicle make, model, year, location, and shop labor rates. Always get multiple quotes for major repairs.
Related OBD-II Trouble Codes
These OBD codes are commonly associated with this warning light. Scan your vehicle with an OBD-II scanner to get the exact code before diagnosing.