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Your vehicle is equipped with oxygen (O2) sensors that help maintain the correct air-fuel ratio in your engine. Once the powertrain control module (PCM) detects an issue with any of these sensors and the data they provide, it’ll check for faults and log an error code. P1131 is a trouble code related to oxygen sensor 1 in bank 1.

What Does the P1131 Code Mean?

Diagnostic trouble code (DTC)  P1131 stands for “Lack of Upstream to the Heated Oxygen Sensor Switch.”

upstream oxygen sensor triggers p1131 code
The code is set when the PCM detects that sensor 1 in bank 1 is sensing too much oxygen.

The code is set when the PCM detects that sensor 1 in bank 1 is sensing too much oxygen. This means that it’s detecting a “lean condition,” and your upstream O2 sensor is not switching from lean to rich within the timeframe set by your manufacturer.

See also  P0131: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)

Code P1131 is commonly logged on several Ford vehicles, but other makes and models can register it.

You can learn more about how issues with O2 sensor operation can result in codes like P1131 in our technical discussion about what oxygen sensors do.

Note: The definition of the P1131 code can be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What Are the Common Causes of the P1131 Code?

What Are the Common Symptoms of the P1131 Code?

How to Diagnose the P1131 Code

The P1131 is a tricky code to diagnose. There is no one solution that can work for all vehicles. If you’re trying to find diagnostic steps for this trouble code, make sure you include your ride’s make and model.

See also  P0136 Code: O2 Sensor Circuit (Bank 1, Sensor 2)

If you’re not sure how to diagnose the issue, it’s best to take your vehicle to an auto repair shop for a proper diagnosis. If you’re an experienced DIYer, you can go ahead and do it yourself.

How to Fix the P1131  Code

Resolving a P1131 can be hard, especially if you don’t have in-depth knowledge about O2 sensors and vehicle repair in general. Remember that you can always get a professional mechanic to check the problem for you.

If you’re a seasoned DIYer, make sure you have the right repair tools before starting the repair. Also, read up about the issue first to ensure that you’re doing the repair steps that apply to your vehicle.

Vehicle-specific guides from resources like Chilton or an ALLDATA subscription might have the information you need to clear this trouble code.

About The Author
Richard McCuistian, ASE Certified Master Automobile Technician
Reviewed By Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

CarParts Research Team
Written By Research Team

Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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