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P1172 Honda Code - Air Fuel Ratio Sensor Circuit Out of Range High

Quick Answer

The P1172 diagnostic trouble code (DTC) indicates that the rear air-fuel (A/F) sensor located on Bank 1 is reporting a voltage signal that is higher than the expected range. Common causes include Faulty rear A/F sensor: The sensor itself may be malfunctioning due to wear and tear or contamination, Wiring issues: Damaged or corroded wiring and connectors leading to the sensor can cause incorrect readings, Vacuum leaks: Air leaks in the intake system can lead to an incorrect air-fuel mixture, affecting sensor readings. 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
P1172 Honda indicates Air Fuel Ratio Sensor Circuit Out of Range High.
Common causes
Common causes include Faulty rear A/F sensor: The sensor itself may be malfunctioning due to wear and tear or contamination, Wiring issues: Damaged or corroded wiring and connectors leading to the sensor can cause incorrect readings, Vacuum leaks: Air leaks in the intake system can lead to an incorrect air-fuel mixture, affecting sensor readings.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 02, 2025
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Code P1172 Honda Description

The P1172 diagnostic trouble code (DTC) indicates that the rear air-fuel (A/F) sensor located on Bank 1 is reporting a voltage signal that is higher than the expected range. This sensor, also known as an oxygen sensor, plays a critical role in monitoring the air-fuel mixture entering the engine. It sends real-time data to the engine control unit (ECU), which adjusts the fuel injection and ignition timing to optimize performance, fuel efficiency, and emissions. When the sensor's output is too high, it suggests that the engine is running lean (too much air compared to fuel), which can lead to various performance issues.
OBDII Code P1172 Honda - Air Fuel Ratio Sensor Circuit Out of Range High
P1172 Honda Code - Air Fuel Ratio Sensor Circuit Out of Range High

Common Causes of P1172 Honda

  1. Faulty rear A/F sensor: The sensor itself may be malfunctioning due to wear and tear or contamination.
  2. Wiring issues: Damaged or corroded wiring and connectors leading to the sensor can cause incorrect readings.
  3. Vacuum leaks: Air leaks in the intake system can lead to an incorrect air-fuel mixture, affecting sensor readings.
  4. Fuel delivery problems: Issues such as a clogged fuel filter or failing fuel pump can result in inadequate fuel supply.
  5. Exhaust leaks: Leaks in the exhaust system can introduce excess oxygen, skewing the sensor's readings.

Symptoms of P1172 Honda

  1. Decreased fuel efficiency: The vehicle may consume more fuel than usual due to improper air-fuel mixture adjustments.
  2. Rough idling: The engine may exhibit unstable idling or stalling, particularly when the vehicle is at a stop.
  3. Poor acceleration: There may be noticeable hesitation or lack of power during acceleration.
  4. Check Engine Light: The illumination of the check engine light on the dashboard, indicating a fault in the engine management system.
  5. Increased emissions: The vehicle may fail emissions tests due to improper combustion caused by the faulty sensor.

How to Fix P1172 Honda

  1. Diagnostic Scan: Begin by using an OBD-II scanner to confirm the P1172 code and check for any additional codes that may provide further insight into the problem.
  2. Visual Inspection: Inspect the wiring and connectors leading to the rear A/F sensor for any signs of damage, corrosion, or loose connections.
  3. Sensor Testing: Test the rear A/F sensor using a multimeter to check its voltage output and compare it to manufacturer specifications. If it is out of range, replace the sensor.
  4. Check for Leaks: Inspect the intake and exhaust systems for any vacuum or exhaust leaks that could affect air-fuel mixture readings.
  5. Fuel System Inspection: Evaluate the fuel delivery system, including the fuel pump and filter, to ensure they are functioning correctly and providing adequate fuel pressure.

Cost to Fix P1172 Honda

The cost to repair a P1172 code can vary widely based on the specific issue and the vehicle's make and model. Typically, replacing an A/F sensor can range from $150 to $300, including parts and labor. If additional repairs are needed, such as fixing wiring issues or addressing fuel delivery problems, costs can increase significantly. Labor rates can vary, with most auto repair shops charging between $80 and $150 per hour. Rates may be higher in metropolitan areas or at dealerships, while independent shops may offer lower rates. It is advisable to check local rates for a more precise estimate and to consider that diagnosis time may also impact the overall cost.

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Information for Specific Honda Models

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 P1172 Honda Code

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  • Having problem with p1172 and P2a00 codes popping up also having miss fire's is that do to p0339 code as well

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  • What model and year is your Honda? you may have to have a valve adjustment. If the valves are not adjusted properly, the engine may have a misfire and trigger air/fuel ratio codes.

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  • My 2017 Honda CR-V Touring is throwing codes P1172, P2A00, PO134, and UO199. Bank 1, Sensor 1 is affected. I also recently got a new battery and had loss of power when installing it. Some of the systems are incomplete as to readiness; however this one is listed as Complete and Fail.

    The problems started in the severe cold and after spinning tires to get up a hill in the ice and snow. (I don’t know if that’s relevant or not.)

    Ideas?

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  • All codes point to faulty Air/Fuel Ratio Sensor Bank 1 Sensor 1. Start by checking the sensor connector. If the connector is not damage or disconnected, then you must replace the sensor.

    P1172 HONDA - Rear A/F Sensor Bank 1 Sensor 1 Circuit Out Of Range High
    Read more: https://www.autocodes.com/p...

    P2A00 HONDA - Air/Fuel Ratio Sensor 1 Bank 1 Circuit Range/Performance Problem
    Read more: https://www.autocodes.com/p...

    P0134 HONDA - Air/Fuel Ratio Sensor Bank 1, Sensor 1 Heater System Malfunction
    Read more: https://www.autocodes.com/p...

    The U0199 code is not related to the Air/Fuel Ratio Sensor.

    U0199 HONDA - Immobilizer-Keyless Control Unit Lost Communication With Door Multiplex Control Unit
    Read more: https://www.autocodes.com/u...

    Reply to Comment