P0140 - O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)

An oxygen sensor circuit issue was detected.

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

Code Overview

An oxygen sensor circuit issue was detected.

Common Causes

• Failed downstream oxygen sensor on bank 1 sensor 2
• Damaged wiring or poor terminal contact in the sensor circuit
• Exhaust leak affecting the downstream reading
• Sensor stuck inactive because of a separate fueling or catalyst problem

Symptoms

• Check-engine light with little or no drivability change
• Failed emissions readiness or inspection
• Downstream O2 data may stay flat on the scan tool

Diagnostic Steps

1. Check for exhaust leaks and catalyst-related codes first
2. Inspect the bank 1 sensor 2 wiring and connector near the exhaust
3. Watch downstream sensor activity on the scan tool after warm-up
4. Verify power, ground, and signal integrity before replacing the sensor

Repair Difficulty

Moderate

General difficulty estimate for the most common repair path.

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.