Common Symptoms
- Check engine light illuminated
- Reduced engine power or derate
- Poor fuel economy
- Diesel exhaust fluid consumption higher than normal
- Failed emissions test
- SCR system efficiency warning message
Most Likely Root Causes
- Faulty NOx sensor
- Exhaust leak upstream of NOx sensor
- Contaminated or fouled NOx sensor element
- Damaged wiring harness or connector corrosion
- Failing SCR catalyst affecting sensor readings
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Component Location
The NOx sensor is mounted in the exhaust system downstream of the diesel particulate filter and upstream or downstream of the SCR catalyst.
Manufacturer Notes
NOx sensors on modern diesel engines require periodic replacement as maintenance items and are sensitive to exhaust contamination and thermal cycling.
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