P0137 - O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)

Downstream O2 sensor signal voltage low (B1S2).

Treat the code as the starting point: compare symptoms, likely causes, and repair paths before pricing parts or moving into an estimate.

Code Overview

Downstream O2 sensor signal voltage low (B1S2).

Common Causes

• O2 sensor failure
• Wiring issue
• Exhaust leak
• Lean condition

Diagnostic Steps

1. Inspect exhaust for leaks
2. Inspect sensor wiring
3. Verify activity on scan tool

Likely Repairs & Cost Guides

Use symptoms, scan data, and quick checks to confirm the likely repair path before pricing parts. The estimator helps compare repair paths before replacing anything unnecessarily.

Related OBD Codes

Browse nearby code-family pages when the same fault pattern overlaps across systems, such as misfire, lean fuel trim, EVAP sealing, cooling, or charging faults.

Next Steps

Move from code lookup to diagnosis, then estimate the likely repair only after symptoms, causes, and checks point to the same path.