AutoCodes – Generic – P1131

P1131 Code - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1

Quick Answer

The Heated Oxygen Sensor (HO2S) Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration that can affect emissions. Common causes include Faulty Upstream Oxygen Sensor Bank 1, Fuel pressure high or low, MAF sensor dirty/defective. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1131 indicates Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1.
Common causes: Common causes include Faulty Upstream Oxygen Sensor Bank 1, Fuel pressure high or low, MAF sensor dirty/defective.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 51,815

How popular is this code, among other codes? Medium

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 29, 2022

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P1131 Description

The Heated Oxygen Sensor (HO2S) Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration that can affect emissions. Under specific conditions, the fuel control or upstream HO2S sensors are checked for proper output voltage and response rate (the time it takes to switch from lean to rich or rich to lean). Downstream HO2S sensors used for Catalyst Monitor are also monitored for proper output voltage. Input is required from the Engine Coolant Temperature (ECT) or Cylinder Head Temperature (CHT), Inlet Air Temperature (IAT), Mass Air Flow (MAF), Throttle Position (TP) and Crankshaft Position (CKP) sensors to activate the HO2S Monitor. The Fuel System Monitor and Misfire Detection Monitor must also have completed successfully before the HO2S Monitor is enabled.
• The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1 for gasoline engines), the HO2S will generate a voltage between zero and 0.45 volt. Rich of stoichiometric, the HO2S will generate a voltage between 0.45 and 1.0 volt.
• The HO2S Monitor evaluates both the upstream (Fuel Control) and downstream (Catalyst Monitor) HO2S for proper function.
• Once the HO2S Monitor is enabled, the upstream HO2S signal voltage amplitude and response frequency are checked. Excessive voltage is determined by comparing the HO2S signal voltage to a maximum calibratable threshold voltage.
• A fixed frequency closed loop fuel control routine is executed and the upstream HO2S voltage amplitude and output response frequency are observed. A sample of the upstream HO2S signal is evaluated to determine if the sensor is capable of switching or has a slow response rate.
• An HO2S heater circuit fault is determined by turning the heater on and off and looking for a corresponding change in the OSM and by
measuring the current going through the heater circuit.
• The MIL is activated after a fault is detected on two consecutive OBDII drive cycles.

OBDII Code P1131 - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1 - AutoCodes.com — P1131 Code - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1

What does this mean?

What are the Possible Causes of the DTC P1131?

Faulty Upstream Oxygen Sensor Bank 1
Fuel pressure high or low
MAF sensor dirty/defective
Vacuum leak on engine
Leaking fuel injector or fuel pressure regulator
Faulty Powertrain Control Module (PCM)

How to Fix the DTC P1131?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

The code means that the Powertrain Control Module (PCM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1131 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P1131 code?

Need more information on how to fix the P1131 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1131 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P1131 Audi — HO2S21 Inner Resistance Too Large
P1131 BMW — Oxygen Sensor Behind Catalytic Converter 2 Ageing
P1131 Buick — HO2S Circuit Low Variance Bank 1 Sensor 2
P1131 Cadillac — HO2S Circuit Low Variance Bank 1 Sensor 2
P1131 Chevrolet — HO2S Circuit Low Variance Bank 1 Sensor 2
P1131 Chrysler — Glow Plug Control Module Internal Fault-Voltage Supply Concern
P1131 Ford — Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
P1131 GMC — HO2S Circuit Low Variance Bank 1 Sensor 2
P1131 Hyundai — Injection Quantity Adjust
P1131 Infiniti — Swirl Control Valve Control Solenoid Valve
P1131 Lincoln — Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
P1131 Mazda — Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank 1
P1131 Mercury — Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
P1131 MINI — Oxygen Sensor Behind Catalytic Converter 2 Ageing
P1131 Nissan — Swirl Control Valve Control Solenoid Valve
P1131 Pontiac — HO2S Circuit Low Variance Bank 1 Sensor 2
P1131 Subaru — Front Oxygen Sensor Circuit Malfunction Short Circuit
P1131 Suzuki — HO2S11 Circuit Low Voltage Shift/High Voltage
P1131 Volkswagen — HO2S21 Inner Resistance Too Large

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P1131 Code

No Frequently Asked Questions about P1131 Code found.

Discuss the causes and fixes for P1131 OBDII Code

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Nick Inferrera
Date: August 18, 2016 at 1:38 am

My 2002QX4 SUV DOES NOT START, BUT IT CRANKS.. THE CODE READ OUT P1131

Reply to Comment
OBDIITech
Date: August 18, 2016 at 5:44 am

There must be something else causing the problem, a bad Oxygen Sensor will not cause a no start problem. I suggest starting by checking for fuel pressure. Does the "Security Light" stays solid ON when you crank the engine? If it does, then the problem is key.

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