O2 Sensor Circuit High Voltage Bank 2 Sensor 2
The engine control module (PCM) has detected that the voltage signal from the downstream oxygen sensor on Bank 2 (Sensor 2) is remaining abnormally high for an extended period. This typically means the sensor is reporting a constant rich condition or there is a short to voltage in the sensor's wiring circuit.
This code primarily affects emissions monitoring and rarely causes severe drivability issues. However, it should be addressed to ensure the vehicle passes emissions testing and to prevent potential long-term damage to the catalytic converter if a true rich condition exists.
Common symptoms
- Illuminated Check Engine Light
- Failed state emissions test
- Slight decrease in fuel economy
- Strong exhaust smell if the engine is actually running rich
- Usually no noticeable drivability issues
Likely causes
- Faulty Bank 2 Sensor 2 oxygen sensor
- Short to voltage in the O2 sensor signal wire
- Corroded, damaged, or loose O2 sensor connector
- Engine running excessively rich on Bank 2 (e.g., leaking fuel injector)
- Faulty Powertrain Control Module (PCM)
What to check before replacing parts
Visually inspect the Bank 2 Sensor 2 wiring harness and connector.
Look for: Look for melted wires from exhaust heat, chafing, corrosion, or water intrusion that could cause a short circuit.
Monitor the O2 sensor voltage using a scan tool with the engine running.
Look for: The voltage should fluctuate slightly but remain mostly steady between 0.45V and 0.8V on a warm catalyst; if it is stuck above 1.0V, the circuit voltage is too high.
Disconnect the Bank 2 Sensor 2 and observe the scan tool data.
Look for: If the voltage drops to a baseline (usually around 0.45V) when disconnected, the sensor is likely internally shorted. If it remains high, the wiring harness has a short to voltage.
Test the signal wire for a short to battery voltage using a digital multimeter.
Look for: With the sensor disconnected and ignition on, check for 12V or 5V on the signal wire where there shouldn't be, which indicates a short to power in the harness.
Check long-term and short-term fuel trims for Bank 2.
Look for: Highly negative fuel trims indicate the engine is actually running rich, which could be causing the high O2 sensor reading rather than a sensor or circuit fault.
This page explains the generic P0158 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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