P0136 - O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)

Downstream O2 sensor circuit issue (B1S2).

Code first. Confirm symptoms and checks before pricing parts.

Explore Related Systems

Compare nearby repair families.

Common Next Steps

Turn the code into the next check.

Related Inspection

Code Overview

Downstream O2 sensor circuit issue (B1S2).

Common Causes

• Failing downstream oxygen sensor on bank 1 sensor 2
• Wiring or connector fault in the sensor circuit
• Exhaust leak ahead of the downstream sensor
• Catalyst issue affecting downstream sensor behavior

Symptoms

• Check-engine light with little or no drivability complaint
• Failed emissions readiness or inspection
• Downstream O2 data may appear flat or erratic

Diagnostic Steps

1. Inspect the bank 1 sensor 2 wiring and connector near the exhaust
2. Check for exhaust leaks ahead of the downstream sensor
3. Verify downstream sensor activity on the scan tool after warm-up
4. Look for catalyst-related companion codes before replacing parts

Repair Difficulty

Moderate

General difficulty estimate for the most common repair path.

Likely Repairs & Cost Guides

Confirm the repair path before pricing parts.

Related OBD Codes

Browse nearby codes when systems overlap.

Next Steps

Move from code to checks, then estimate.