O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
The P0140 code indicates that the Engine Control Module (ECM) has detected no activity from the oxygen sensor located after the catalytic converter on Bank 1 (the side of the engine with cylinder #1). This sensor monitors the catalytic converter's efficiency. The ECM expects a fluctuating voltage signal from the sensor; when it remains at a fixed voltage (typically around 0.45V) or shows no change, it sets this code. Common causes include a faulty sensor, wiring issues, exhaust leaks, or a failed catalytic converter.
01. Most Common Causes
- Faulty oxygen sensor (Bank 1 Sensor 2)
- Damaged or corroded wiring/connectors
- Exhaust leak before the sensor
- Failed catalytic converter
- Blown fuse or ECM issue
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Decreased fuel economy
- Possible rough idle or hesitation
03. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P0140 is present. Check freeze frame data.
Step 2: Visually inspect the O2 sensor wiring and connector for damage or corrosion.
Step 3: Use a multimeter to check sensor heater circuit resistance and voltage supply.
Step 4: Monitor O2 sensor voltage with a scan tool; if stuck at 0.45V, suspect sensor or wiring.
Step 5: Check for exhaust leaks upstream of the sensor using a smoke machine or soapy water.
Step 6: If all else is fine, replace the O2 sensor (Bank 1 Sensor 2).
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause poor fuel economy and increased emissions. Prolonged driving could damage the catalytic converter.
How much does it cost to fix?▼
Typically $50-$150 for a DIY sensor replacement, or $150-$300 at a shop including labor.