Emission Control System Performance
The engine control module has detected a performance issue in the emission control system.
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What it means (plain English)
The engine's computer is saying the emission controls aren't working like they should, which can cause increased pollution and may affect how the engine runs.
What the computer is actually seeing
The engine control module monitors various sensors and components in the emission control system; it expects certain performance and efficiency but sees values that are outside its normal range, likely due to a faulty component or system blockage.
What a healthy reading looks like
Normal operation should show exhaust gas recirculation (EGR) flow between 20-50% under load, NOx sensor readings typically range from 0 to 500 ppm depending on conditions, and diesel particulate filter (DPF) pressure differential not exceeding 5 inches of water at idle.
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. Inspect wiring and connectors to the emission control components for fraying or corrosion. Repair as necessary. Decision: if wiring is damaged, repair it and clear codes. If not, proceed.
- 22. Check the EGR valve operation by applying vacuum/pressure to see if it opens and closes correctly. Expect to see it move smoothly. Decision: if it doesn't actuate properly, replace the EGR valve.
- 33. Perform a visual inspection of the DPF and check for signs of blockage or excessive soot buildup. Use a pressure gauge to measure DPF differentials. Decision: if differential pressure is over 5 in. H2O, clean or replace the DPF as needed.
- 44. Test the NOx sensors for electrical issues and confirm readings during operation. Use scan tools to monitor live data. Decision: if the readings are out of expected range, replace the NOx sensors.
Common causes
- Blocked or faulty EGR valve
- Failure in the DPF system
- Faulty NOx sensors
- Leaking or damaged hoses in the emission control system
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable but you may experience increased emissions and poor engine performance. Fix sooner rather than later.
Will this code come back after clearing?
If the underlying issue isn't resolved, the code will likely return.
Why does this code relate to the DPF system?
Because performance issues in the emission control system can often stem from problems with the DPF, especially if it is clogged.
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