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

An oxygen sensor circuit issue was detected.

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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

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