Engine Aftertreatment System - Emission Control System Fault
Fault detected in the emissions control system of the engine aftertreatment.
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What it means (plain English)
The computer in the truck sees that the emissions control system isn't working right, which can increase pollution and affect performance.
What the computer is actually seeing
The engine control module (ECM) is monitoring sensors in the aftertreatment system, like NOx sensors and temperature sensors. If readings are out of the normal range, it triggers the fault code.
What a healthy reading looks like
Normal NOx sensor operation shows values typically between 0-5 volts, and the exhaust temperature should be between 400-800°F in normal conditions.
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 wiring and connectors related to the NOx sensors for damage or corrosion. - If wiring/connectors are fine, proceed to step 2. - If damaged, repair/replace as needed.
- 22. Inspect the NOx sensors using a scan tool to check for proper operation and voltage. - If the sensor readings are out of spec, replace the faulty sensor. - If readings are normal, proceed to step 3.
- 33. Check exhaust temperatures with a pyrometer to ensure the aftertreatment system is functioning correctly. - If temperatures are low (below expected values), this may indicate a blockage or fault in the system. - If temperatures are in range, proceed to step 4.
- 44. Inspect and test the EGR system for proper operation. - If EGR issues are found, repair or replace components as necessary. - If EGR is working fine, check for physical blockages in the aftertreatment system.
Common causes
- Faulty NOx sensors
- Blocked exhaust aftertreatment system components
- Wiring issues or poor connections
- Faulty EGR valve or system
- Dirt or soot buildup in the aftertreatment system
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this fault code?
No, it's not safe to drive. It can lead to increased emissions and may cause further damage to the aftertreatment system.
Will this code come back after clearing?
Yes, if the underlying issue isn't fixed, the code will likely return after a few cycles.
Why does this code pair with SPN 3361?
SPN 3361 is related to NOx sensor issues which often contribute to emissions control faults.
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