P0140: O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)
Updated November 14, 2026
The bank 1 sensor 2 oxygen sensor sits after the catalytic converter and is used mainly to check how well the converter is working. P0140 means its signal isn't moving at all once the engine is warm; it's stuck near the steady value the computer sees when no sensor signal is coming in, which usually means a dead sensor or an open circuit.
COMPZA may earn a commission when you buy through links on this page, at no extra cost to you. How we make money.
🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- A failed downstream oxygen sensor
- A failed heater inside the sensor, so it never warms up enough to work
- An open or damaged wire, or a loose or corroded connector, often from heat near the exhaust
- An engine computer fault (less common)
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Check engine light, usually with no change in how the car drives
- A failed emissions test or readiness monitors that won't complete
- Sometimes a heater code such as P0141 at the same time
Is it safe to drive?
Usually safe to drive with a steady light; this sensor mostly monitors the converter. Get it fixed before an emissions test, and if the light ever flashes, stop driving and get it checked.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Scan for a heater code (P0141) or other O2 codes first.
- Fully warm up the engine, then watch the bank 1 sensor 2 reading in live data during a drive. A working sensor moves at least somewhat, especially when you let off the gas; a flat line points to the sensor or wiring.
- With the engine off and the exhaust cool, inspect the sensor wiring for melted insulation or wires rubbing on the exhaust, and check the connector.
- Use an O2 sensor socket and penetrating oil to remove it, and keep hands clear of the belts and fan if you test with the engine running.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
Code readers and scanners in stock
From partner stores' live product feeds. Check that the tool covers your vehicle's make, model and year on the retailer's page before you buy.
LAUNCH CR319 OBD2 Code Reader & Emissions Readiness Tester$24.99at LAUNCH X431 Online 
LAUNCH CR529 OBD2 Code Reader with Live Data Stream$45at LAUNCH X431 Online 
Autel MaxiLink ML529$52at AUTELOnline 
AutoLink AL319$59at AUTELOnline 
MaxiAP AP2500E$60at AUTELOnline 
LAUNCH Creader VII+ Code Reader for Engine, ABS, SRS & Transmission$119at LAUNCH X431 Online Affiliate links. AUTELOnline prices updated Nov 14, 5:26 PM EST · LAUNCH X431 Online prices updated Nov 14, 4:18 PM EST.
Search eBay for your vehicle
Affiliate links: COMPZA may earn a commission from qualifying eBay purchases at no extra cost to you. Add your vehicle in eBay's parts finder to see parts that fit.
Questions
What does P0140 mean?
P0140 is the generic OBD2 code for "O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)." The bank 1 sensor 2 oxygen sensor sits after the catalytic converter and is used mainly to check how well the converter is working. P0140 means its signal isn't moving at all once the engine is warm; it's stuck near the steady value the computer sees when no sensor signal is coming in, which usually means a dead sensor or an open circuit.
Is it safe to drive with P0140?
Usually safe to drive with a steady light; this sensor mostly monitors the converter. Get it fixed before an emissions test, and if the light ever flashes, stop driving and get it checked.
How do I check P0140 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Scan for a heater code (P0141) or other O2 codes first. Fully warm up the engine, then watch the bank 1 sensor 2 reading in live data during a drive. A working sensor moves at least somewhat, especially when you let off the gas; a flat line points to the sensor or wiring. With the engine off and the exhaust cool, inspect the sensor wiring for melted insulation or wires rubbing on the exhaust, and check the connector. Use an O2 sensor socket and penetrating oil to remove it, and keep hands clear of the belts and fan if you test with the engine running.
Related codes
📬 Get the weekly deals email
One email a week with the best current deals from our partner stores: home, kitchen, tech, car and gifts. No spam, unsubscribe anytime.
Emails include affiliate links; COMPZA may earn a commission at no extra cost to you. See our privacy policy.