Common Symptoms
- Check Engine Light illuminated
- Reduced engine power or derate condition
- Poor fuel economy
- Increased diesel exhaust fluid (DEF) consumption
- Failed emissions test
Most Likely Root Causes
- Failed NOx sensor
- Damaged wiring harness or connectors to NOx sensor
- Corroded or loose electrical connections
- ECM software calibration issue
- Exhaust system leaks near sensor location
Full step-by-step tests, DVOM guidance, and pinout data are available inside the AI Diesel Tech diagnostic session.
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Component Location
NOx sensor is typically mounted in the exhaust system downstream of the diesel particulate filter or SCR catalyst.
Manufacturer Notes
Many diesel manufacturers require specific diagnostic software tools to properly monitor NOx sensor operation and perform guided diagnostics.
Also diagnosing J1939 SPN/FMI codes?
Heavy-duty trucks often throw both OBD-II and J1939 faults simultaneously. AI Diesel Tech handles both protocols in a single guided session.
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