Reductant System Performance
This code indicates performance issues within the reductant system, affecting emissions control.
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 monitors the urea injection system (DEF) for how well it reduces NOx emissions. If it detects the system isn't working as efficiently as it should, it sets this code, meaning emissions could be too high.
What the computer is actually seeing
The engine control module (ECM) tracks the amount of reductant (urea) injected into the exhaust. It expects a certain rate and timing of injection based on calculations of exhaust flow and NOx levels. If the measured values deviate significantly from expected parameters, the code is triggered.
What a healthy reading looks like
Urea injection should occur between 0.1 to 10 mm³ per injection event and the system should operate with a temperature more than 0°C (32°F) for proper function. Pressure in the chamber must remain between 1-3 bar during operation.
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 urea fluid level in the tank. Refill if low.<br>Decision: If level was low, fill and clear code.<br>If level is good, continue to step 2.
- 22. Inspect urea injector for clogs or damage. Clean or replace if necessary.<br>Decision: If injector was clogged and cleaned/replaced, clear code and retest.<br>If no issues found, continue to step 3.
- 33. Check for leaks in the urea lines and fittings. Repair any leaks found.<br>Decision: If leaks were repaired, clear code and retest.<br>If no leaks found, continue to step 4.
- 44. Test NOx sensors for proper operation. Replace if faulty.<br>Decision: If sensors were replaced, clear code and retest.<br>If sensors are okay, continue to step 5.
- 55. Check for ECM software updates—apply if available and necessary.<br>Decision: If updates applied, clear codes and retest.
Common causes
- Faulty urea injector
- Low urea fluid level
- Leaking urea lines
- Dirty or faulty NOx sensors
- ECM software issue
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Not recommended; it could affect emissions and lead to further issues.
Will the code come back?
If the underlying issue isn't fixed, yes, it will come back.
Why does this code pair with other codes?
Other codes may indicate additional or related issues in the emissions control system.
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