What this code means

The PCM detected a problem with the heated oxygen sensor warm-up heater control circuit for Bank 1 Sensor 1. The heater circuit is not achieving the expected performance during engine warm-up.

Symptoms

• Check Engine Light
• Poor cold-start emissions
• Slow O2 sensor response when cold
• Poor fuel economy during warmup

Common causes

• Faulty O2 sensor heater
• Heater relay failure
• Corroded connections
• High resistance in heater circuit

Diagnostic steps

1. Test O2 sensor heater resistance
2. Check heater relay operation
3. Inspect wiring for corrosion
4. Monitor heater current with scan tool

Repair notes

Replace O2 sensor if heater element has failed. Check relay and wiring.

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