Front Oxygen Sensor Circuit Malfunction Short

What this code means

The PCM has detected a short circuit condition in the front oxygen sensor circuit. The sensor signal is shorted to ground or to the reference voltage, causing an incorrect fuel mixture reading.

Symptoms

• Check Engine Light
• Engine runs rich or lean depending on short direction
• Poor fuel economy
• Rough idle
• Failed emissions

Common causes

• O2 sensor wiring shorted to ground or voltage
• Internal O2 sensor failure
• Wiring chafed against exhaust or engine components
• Water intrusion in O2 sensor connector
• Heat-damaged wiring insulation

Diagnostic steps

1. Check O2 sensor voltage on scan tool (stuck high or low indicates short)
2. Inspect wiring for chafing or exposed conductors
3. Test for shorts to ground and to voltage in sensor circuit
4. Check connector for water intrusion
5. Disconnect sensor and recheck circuit

Repair notes

Repair the shorted wiring or replace the front O2 sensor if internally shorted.

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