What this code means

The ECU detected that the heater resistance in the upstream oxygen sensor on Bank 1 is outside the specified range. The heater brings the O2 sensor up to operating temperature quickly for accurate fuel trim control.

Symptoms

• Check Engine Light
• Poor cold-start fuel economy
• Extended warmup emissions
• Failed emissions test

Common causes

• Faulty O2 sensor heater element
• High-resistance connection in heater circuit
• Corroded O2 sensor connector
• Blown heater circuit fuse

Diagnostic steps

1. Test O2 sensor heater resistance (should be 2-30 ohms)
2. Check heater circuit fuse
3. Inspect wiring and connector for corrosion
4. Measure voltage at heater circuit

Repair notes

Replace the upstream O2 sensor on Bank 1 if heater resistance is out of specification.

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