P0140: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
Can you still drive? Yes, safe to drive. This is a monitoring sensor and its failure does not directly affect engine performance. Repair before emissions testing.
What Does P0140 Mean?
Code P0140 means the downstream oxygen sensor on Bank 1 is producing a flat, unchanging voltage signal. The ECU expects to see some variation in the downstream O2 sensor output as the catalytic converter processes exhaust gases. A completely flat signal indicates the sensor has likely failed or its circuit is compromised.
Need to read your codes?
An OBD-II scanner lets you read and clear diagnostic trouble codes from your vehicle's computer. Most scanners work with any car made after 1996.
Browse OBD-II Scanners on AmazonCommon Causes
- Failed downstream O2 sensor
- O2 sensor heater failure preventing sensor warm-up
- Open or shorted signal wiring
- Heavily contaminated sensor element
Symptoms
- Check engine light on
- Failed emissions test
- Slight decrease in fuel economy
- No obvious drivability symptoms
Diagnostic Steps
- 1Read and document freeze frame data
- 2Monitor downstream O2 sensor voltage for any activity
- 3Check O2 sensor heater circuit voltage and resistance
- 4Inspect wiring between the ECU and the O2 sensor
- 5Replace downstream O2 sensor if confirmed inactive
Recommended Parts & Tools
oxygen sensor
O2 sensor socket
Estimated Repair Cost
| Type | Estimated Cost |
|---|---|
| Total Repair Cost Range | $50 - $300 |
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Chat with AI About P0140Commonly Affected Vehicles
Related Recalls
1 Active Recall — 2026 Ford F-150
The following NHTSA safety recalls have been issued for this vehicle. Contact your dealer to check if your vehicle is affected.
ELECTRICAL SYSTEM: INTEGRATED TRAILER BRAKE CONTROL
Ford Motor Company (Ford) is recalling certain 2021-2026 F-150, 2022-2026 F-250 SD, F-350 SD, F-450 SD, F-550 SD, Maverick, 2024-2026 Ranger, 2023-2026 F-600 SD, 2022-2027 Lincoln Navigator, Expedition, and 2026 E-Transit vehicles. When towing a trailer, the integrated trailer module (ITRM) may lose communication with the vehicle, possibly causing a loss of brake and turn signal lights, or a loss of brake function. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 108, " Lamps, Reflective Devices, and Associated Equipment."
Remedy: The integrated trailer module software will be updated by a dealer, or through an over-the-air (OTA) update, free of charge. Owner notification letters are expected to be mailed March 17, 2026. Owners may contact Ford customer service at 1-866-436-7332. Ford's number for this recall is 26C10. Vehicle Identification Numbers (VINs) involved in this recall will be searchable on NHTSA.gov beginning March 17, 2026.
Data provided by the National Highway Traffic Safety Administration (NHTSA).
Frequently Asked Questions
Do I need to replace the downstream O2 sensor for P0140?
In most cases, yes. P0140 almost always means the sensor has completely failed and needs replacement. Wiring issues are possible but less common.
Can I use a universal O2 sensor for P0140?
Universal O2 sensors can work but require splicing into the existing connector. A direct-fit sensor is recommended for easier installation and more reliable operation.
Community Fix Reports
Community reports are user-submitted and not verified by Auto AI Buddy. Results may vary.
Related Codes
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