OBD-II diagnostic trouble code
P0138Caution

O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

The rear bank-1 oxygen sensor's voltage is staying persistently high, typically from sensor wear rather than an actual engine fault.

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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 P0138?

You can usually keep driving with P0138, but don't put it off — the underlying cause can get worse or lead to further damage the longer it goes unaddressed. Get it diagnosed as soon as you reasonably can.

How much does it cost to fix P0138?

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

What causes P0138?

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