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 blown fuse.
1. Most Common Causes
- Faulty oxygen sensor (Bank 1 Sensor 2)
- Damaged or corroded wiring/connector
- Exhaust leak before the sensor
- Blown O2 sensor fuse
- ECM failure (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Decreased fuel economy
- Rough idle or hesitation (less common)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the O2 sensor wiring and connector for damage or corrosion.
Step 3: Check the O2 sensor fuse with a multimeter.
Step 4: Using a scan tool, monitor the O2 sensor voltage; if it stays at 0.45V or flatlines, the sensor is likely faulty.
Step 5: Inspect for exhaust leaks upstream of the sensor.
Step 6: If all else is good, replace the O2 sensor.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but you may fail an emissions test and fuel economy may suffer. It's best to fix it soon.
How much does it cost to fix?▼
Typically $50-$150 for a DIY replacement, or $100-$250 at a shop including labor.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.