Common Symptoms
- Check engine light or MIL illuminated
- NOx sensor-related fault codes stored
- Possible derate or reduced engine power on diesel engines
- Increased exhaust emissions during testing
- DEF system warning messages on instrument cluster
Most Likely Root Causes
- Failed NOx sensor heater element
- Damaged or corroded wiring to NOx sensor heater circuit
- Open or short circuit in NOx sensor heater wiring harness
- Faulty NOx sensor itself
- Corroded connector pins at NOx sensor
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Component Location
NOx sensor is mounted in the exhaust system downstream of the diesel particulate filter or SCR catalyst on diesel vehicles.
Manufacturer Notes
Diesel engines with SCR systems require proper NOx sensor heater operation for accurate emissions monitoring and DEF dosing control.
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