OBD-II diagnostic trouble code
P0140Safe to drive

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

The rear bank-1 oxygen sensor's signal is flat, which is a common early sign of sensor failure and is usually low urgency on its own.

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Code names are compiled from open/standardized SAE and ISO references. Explanations, symptoms, causes and fixes are original. Covers generic (P0/C0/B0/U0) codes only — manufacturer-specific codes are planned for a future update.

Frequently asked questions

Can I drive with P0140?

In most cases, yes — P0140 is generally not an urgent safety issue and the car is usually safe to drive for a while. Still, get it checked soon, since the underlying cause can affect fuel economy or emissions the longer it's left.

How much does it cost to fix P0140?

The cost varies too much by cause and vehicle to give a single figure here — a diagnosis will narrow it down.

What causes P0140?

AS
Reviewed by Artyom SemenovAutomotive Editor · Fact-checked by Yauheni Kapliarchuk, Editor-in-Chief
Code names compiled from open SAE/ISO references; explanations and repair guidance are original editorial content
Last verified: 09 Jul 2026 · Our methodology