Common Symptoms
- Check engine light illuminated
- Reduced engine power or derate condition
- Poor fuel economy
- Failed emissions test
- DEF system warning messages on dashboard
Most Likely Root Causes
- Faulty NOx sensor
- Damaged or corroded NOx sensor wiring harness
- Water or contaminant intrusion in sensor connector
- Failed NOx sensor heater circuit
- Engine control module software issue
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Component Location
NOx sensor is typically mounted in the exhaust system downstream of the diesel particulate filter or SCR catalyst on Bank 1.
Manufacturer Notes
NOx sensors in diesel aftertreatment systems are sensitive to contamination from coolant, oil, or improper DEF quality.
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