SCR SYSTEM PERFORMANCE
Indicates a problem with the Selective Catalytic Reduction (SCR) system's performance.
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 SCR system injects a urea solution into the exhaust to reduce emissions. If it's not working, the vehicle can't clean its emissions properly, which is important for passing emissions tests.
What the computer is actually seeing
The Engine Control Module (ECM) compares the NOx sensors' readings before and after the SCR. If the difference is lower than expected, it flags a performance issue.
What a healthy reading looks like
Expected NOx reduction of at least 85%; SCR catalyst inlet temperature should remain above 250°C (482°F) 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 urea tank level. If low, refill and clear codes.
- 22. Inspect wiring and connectors related to the NOx sensors for damage or corrosion. Fix any issues found.
- 33. Test urea injector operation. If it's not spraying, replace it and retest.
- 44. Measure NOx sensor outputs. Using a scan tool, check if the readings are out of expected range (0-1000 ppm). Replace faulty sensor if readings are incorrect.
- 55. Inspect SCR catalyst for blockages or damage. If blocked, replace the catalyst.
Common causes
- Low urea level
- Faulty NOx sensors (inlet or outlet)
- Blocked SCR catalyst
- Leaking urea injector
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Not recommended. It can lead to increased emissions and potential engine performance issues.
Will this code come back after clearing?
It can return if the underlying issue isn't fixed. Monitor continuously until resolved.
Why is this paired with other codes?
SCR issues often connect to NOx sensors or other components in the emissions system.
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