P2204moderate severityPowertrain
NOx Sensor Circuit Intermittent Bank 1
on 2009 Subaru Forester 2.5L H4 · AWD
What this code means
Intermittent signal from the NOx sensor on bank 1.
Symptoms
- Intermittent check engine light
- Erratic SCR operation
Common causes
- Loose connection
- Damaged wiring
- Sensor connector moisture ingress
Diagnostic steps
- Wiggle test wiring and connector
- Check for water intrusion
- Monitor signal stability
Repair notes
Clean and secure connector. Replace sensor or repair wiring if intermittent.
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