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

P0158 means the downstream oxygen sensor on bank 2 is staying high or reading richer than expected for too long. The fault can be a biased sensor, damaged wiring, or a real rich-running condition that keeps the signal elevated.

Code Overview

P0158 means the downstream oxygen sensor on bank 2 is staying high or reading richer than expected for too long. The fault can be a biased sensor, damaged wiring, or a real rich-running condition that keeps the signal elevated.

Common Causes

• Failing downstream oxygen sensor on bank 2 sensor 2
• Engine running rich from a separate fuel-control problem
• Short to voltage or wiring damage in the sensor circuit
• Sensor contamination from oil, coolant, or exhaust issues

Symptoms

• Check-engine light with little or no drivability change
• Failed emissions readiness or inspection
• Rich exhaust smell if a fueling fault is also present

Diagnostic Steps

1. Check for rich-running or catalyst-related companion codes first
2. Inspect the bank 2 sensor 2 harness near the exhaust for melting or shorting
3. Verify downstream sensor voltage behavior on the scan tool after warm-up
4. Confirm the engine is not actually running rich before replacing the sensor

Repair Difficulty

Moderate

General difficulty estimate for the most common repair path.

Likely Repairs & Cost Guides

Use test results to confirm the fault before pricing the repair.

Related OBD Codes

Browse the closest code-family pages when the same fault pattern often shows up nearby.

Next Steps

Move from the code to a diagnosis path, then into repair pricing once the fault is confirmed.