top of page
Ford P1131 Code – Lack of HO2S Switch Lean
Limited
Safe to drive :
Ford vehicles only
Applies only to :
Not applicable to :
This explanation does NOT apply to Toyota, BMW, GM, VW, or other manufacturers.
Medium
Severity level :
When Does This Code Appear on the Vehicles
Ford P1131 appears when the PCM cannot achieve a rich condition during fuel control testing.
What This Code means on the Vehicles
On Ford vehicles, P1131 indicates the upstream oxygen sensor on Bank 1 remains lean during closed-loop operation.
Why This is different from a generic OBD2 Code
Ford uses this code to reflect fuel control response, not direct sensor failure.
Common Situations That Trigger This Code
Vacuum leaks; Exhaust leaks before sensor; Fuel delivery issues.
What Will NOT Fix This Code
Replacing catalytic converter; Clearing code without fixing lean condition.
How to Clear This Code on Vehicles
Diagnose unmetered air, exhaust leaks, and fuel delivery before replacing sensors.
Related Manufacturer Specific Codes
Ford P1151; Ford P0171
bottom of page