Common Symptoms
- Check Engine Light illuminated
- Reduced engine power or derate mode
- Poor fuel economy
- Diesel Exhaust Fluid (DEF) consumption abnormal
- Emission system warning messages on dashboard
Most Likely Root Causes
- Faulty NOx sensor
- Damaged or corroded wiring harness to NOx sensor
- Poor electrical connection at NOx sensor connector
- Exhaust leaks near NOx sensor mounting location
- ECM software calibration issue
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Component Location
NOx sensor is mounted in the exhaust system downstream of the diesel particulate filter, typically on Bank 1 exhaust side.
Manufacturer Notes
Some diesel engines require NOx sensor relearn procedures after replacement or software updates to ensure proper aftertreatment system calibration.
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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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