P0158: O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)

What Does P0158 Mean?

Code P0158 is triggered when the downstream oxygen sensor on Bank 2 reports a voltage consistently above 0.9 volts. This high reading indicates the sensor is stuck reading rich, which could be a sensor failure or a signal wiring short. The ECU uses this sensor to verify catalytic converter efficiency, and a stuck-high reading may falsely indicate converter problems.

Common Causes

• Faulty downstream O2 sensor stuck rich
• Short circuit in the O2 sensor signal wire
• Antifreeze contamination of the sensor from a leaking head gasket
• Failing catalytic converter producing abnormal exhaust composition

Symptoms

• Check engine light on
• Failed emissions test
• Possible slight fuel economy decrease
• No major drivability issues

Diagnostic Steps

1. 1Read and document freeze frame data
2. 2Monitor Bank 2 Sensor 2 voltage to confirm stuck-high reading
3. 3Inspect sensor wiring for shorts to voltage source
4. 4Check for coolant in the exhaust as a sign of head gasket leak
5. 5Compare downstream readings between Bank 1 and Bank 2
6. 6Replace downstream O2 sensor if wiring checks pass

Estimated Repair Cost

Frequently Asked Questions