What this code means

The ECM detected a fault in the front (upstream) heated oxygen sensor on Bank 1. The sensor signal or heater circuit is not operating within specification.

Symptoms

• Check Engine Light
• Poor fuel economy
• Rough idle
• Failed emissions test

Common causes

• Faulty O2 sensor Bank 1
• O2 sensor heater failure
• Exhaust leak near sensor
• Wiring damage to sensor
• Connector corrosion

Diagnostic steps

1. Test O2 sensor signal voltage and switching rate
2. Test heater circuit resistance
3. Check for exhaust leaks near sensor
4. Inspect wiring and connector
5. Compare Bank 1 vs Bank 2 sensor performance

Repair notes

Replace the front heated O2 sensor on Bank 1.

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