Pure Ammonia Concentration High
The PCM has detected a high concentration of pure ammonia.
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 system is reading too much ammonia, which can mean the SCR is overloaded or there's a leak in the DEF system.
What the computer is actually seeing
The engine control module measures the ammonia level in the exhaust and considers it too high based on predefined thresholds.
What a healthy reading looks like
Ammonia concentration should be below 20 ppm (parts per million) during normal 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 DEF fluid level; refill if low. Decision: If low, refill and retest.
- 22. Inspect the DEF lines for leaks or damage. Decision: If found, repair lines and retest.
- 33. Verify the function of the DEF pump. Use a scan tool to check for pump operation. Decision: If not operating, replace DEF pump.
- 44. Test the ammonia sensor; check wiring and connector integrity. Decision: If damaged, repair or replace sensor and retest.
- 55. Monitor ammonia levels with a scan tool during operation. Decision: If levels remain high, investigate and replace the SCR if necessary.
Common causes
- DEF pump malfunction
- Leaking DEF injector
- Blocked or damaged DEF line
- Faulty SCR catalyst
- Inaccurate ammonia sensor reading
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Has it been a long-term issue? This could lead to SCR damage.
Will this code come back after clearing?
Yes, if the underlying issue isn't resolved, it will likely return.
Why does it pair with SPN 4563?
SPN 4563 indicates low ammonia levels, which means there may be inconsistencies in the DEF system, affecting readings.
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