P0131 O2 Sensor Circuit Low Voltage Bank 1 Sensor 1

P0131 indicates low voltage on the bank 1 sensor 1 oxygen-sensor circuit. The upstream signal is lower than expected and may be circuit-related or mixture-related.

Code status

Needs verification

Not yet verified against SAE J2012_202509 / J2012DA. Treat unverified rows as a lookup aid, not repair authority.

System
Fuel / Air
Scope
iso-sae-controlled-p0
Standard
SAE J2012 / ISO 15031-6
Source
legacy-import

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not assume low voltage proves a bad sensor; a real lean condition or signal-circuit problem can create the same code.

Useful checks before replacing parts

Related OBD-II codes

These nearby fuel / air entries can help compare wording and fault area. They may share the same verification status as the source database.