Reductant System Performance
The reductant system is not performing as expected.
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 computer monitors how well the DEF (diesel exhaust fluid) system reduces emissions and it’s detecting that it’s not working right.
What the computer is actually seeing
The PCM sees that the NOx levels are higher than expected after the DEF injection, indicating reduced efficiency of the SCR system.
What a healthy reading looks like
NOx sensor voltage should be within 0.1-4.5 volts; if 0.1 volts with active codes, indicates no NOx reduction.
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 the DEF level – it should be above the minimum threshold.
- 22. Inspect DEF for contamination or freezing (should be clear and odorless).
- 33. Check wiring and connectors to the DEF pump and sensors for damage or corrosion.
- 44. Measure NOx sensor voltage during operation; it should vary between 0.1-4.5 volts.
- 55. If NOx readings are abnormal, inspect the SCR catalyst for damage or blockage.
Common causes
- Low DEF level
- Contamination of DEF
- Faulty DEF injection system
- NOx sensor malfunction
- Leaky exhaust aftertreatment system
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable but may affect emissions and cause limping if the system is severely damaged.
Will this code come back after clearing?
If the underlying issue isn't resolved, yes, the code will likely reappear.
Why is this paired with other codes?
This relates to the overall performance of the emission reduction system, which can affect and be affected by multiple components.
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