P2209moderate severityPowertrain
NOx Sensor Heater Sense Circuit Intermittent
on 2003 Audi A6 3.0L V6 · AWD
What this code means
The PCM detects an intermittent fault in the NOx sensor heater sensing circuit. This can affect emissions monitoring and aftertreatment performance.
Symptoms
- Check engine light on
- Intermittent emissions warning
- Reduced aftertreatment efficiency
Common causes
- Loose or corroded NOx sensor connector
- Damaged NOx sensor heater wiring
- Faulty NOx sensor
- Intermittent ground or power fault
Diagnostic steps
- Scan for related NOx codes
- Inspect sensor connector and wiring
- Wiggle-test harness while monitoring data
- Replace NOx sensor if wiring checks out
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