Oxygen sensor 2 is the downstream oxygen sensor in relationship to the catalytic converter. It measures the amount of air and fuel coming out of the catalytic converter to ensure the catalytic converter is functioning properly. If the voltage is high approx. If the voltage is low approx. Therefore, the downstream oxygen sensor sensor 2 should produce a steady voltage of approximately 0. When trouble code P is set, this indicates that there is a high voltage steadily above.

It is okay to drive a vehicle with P for a short period of time, but driving with this code for an extended period of time can damage the catalytic converter s.

Replacing the O2 sensor without checking to see if the vehicle is running rich due to another problem. For error code P, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. Now I know to check the entire system. I went ahead and replaced both of the 02 sensors, now after 2 days the code po came on.

Had cat replaced 30 days ago,no ck engine light ever came on. Now ck engine light came on bank one sensor 2. I replaced that o2 sensor. Now light came back on.

Please help. Check for exhaust leak too just to be hackerrank offline had the same fault codes on my nissan checked exhaust and had a medium leak at the flange before bank 2 sensor. Having same issue with my rav 4. Replaced the O2 sensor downstream, check engine light came back 1 day later.

Error Code P0138: O2 Oxygen Sensor Circuit High Voltage Bank 1, Sensor 2

Was recommended that I replace the upstream O2 sensor because it could be causing a false reading on the 2nd O2 sensor. That may be my next step, will post update. I had replaced the O2 sensor but it did not change until the isolator was installed. Amazon has them. They are on Amazon. Thanks for the tip. Can you provide the exact part I should order?

Do you have an install guide i could follow? Yes No This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light is on diagnostic inspection. P is the OBD-II generic code indicating the O2 sensor for bank 1 sensor 2 fails to have a lower voltage output below 1.

The engine control module ECM sees the voltage of the O2 sensor for bank 1 sensor 2 above 1. The engine may run lean during the testing of the sensor to correct the problem and may hesitate or misfire. Monitors O2 sensor data to see if the voltage is switching back and forth between low and high at a fast rate compared to other sensors.

p0138 civic

O2 sensor 1 for bank 1 can be used to diagnose O2 sensor 2 for bank 1 by looking at both sensors operation for comparison. The operation should be nearly the same, except sensor 2 should have a lower O2 reading since the catalyst should burn off the excess fuel and oxygen. The voltage output from the O2 sensor may be due to the exhaust catalyst being broken apart, which can cause the O2 sensors to give high output voltages.

The ECM may not control the fuel-to-air ratio of the engine properly, leading to a clogged catalyst and excessive carbon buildup in the engine with fouled spark plugs. The high voltage condition from the O2 sensor is indicating a lack of oxygen in the exhaust or other related problems, such as a leaking fuel injector or a broken up catalyst inside.

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at Our certified mobile mechanics perform over services, including diagnostics, brakes, oil changes, scheduled mileage maintenances, and will come to you with all necessary parts and tools.

With YourMechanic you can skip the auto shop altogether. They send certified and screened mechanics straight to your door and enable you to save big on car repair and maintenance. Cost of diagnosing the P code. No more waiting rooms! Our mechanics will come to you to diagnose and fix the P code. Excellent Auto Repair Ratings. YourMechanic Auto Repair. Recent Check Engine Light is on Inspection reviews.

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p0138 civic

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P0138 - O2 Sensor Circuit High Voltage Bank 1 Sensor 2

Engine-Codes - Generic - P P Possible Causes What does this mean? How is the P code repair? Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

Tech Notes What does this mean? What is the cost to diagnose the P code Labor: 1. The auto repair labor rates vary widely across the country, and even within the same city. How much do you know about cars? Take the AutoCodes. When is the code detected? The P code is set when the Engine Control Module ECM detects that the rear O2 sensor signal voltage remains excessively high for an extended period of time. For optimum catalyst operation, the air-fuel mixture air-fuel ratio must be maintained near the ideal stoichiometric ratio.

The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The HO2S generates a voltage between 0. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. More Information Need more information on how to fix the P code? Get Access to Factory Service Manuals.

Need more help? Get the P code diagnosed by a professional: Find a repair shop in your area. Why is the Engine Light ON? Repair Importance Level: 2.Play Now. Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors.

Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins. Tech Notes What does this mean? The auto repair labor rates vary widely across the country, and even within the same city. How much do you know about cars? Take the AutoCodes. When is the code detected? The P code is set when the Engine Control Module ECM detects that the rear O2 sensor signal voltage remains excessively high for an extended period of time.

For optimum catalyst operation, the air fuel mixture air-fuel ratio must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The HO2S generates a voltage between 0. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. Get Access to Factory Service Manuals. Need more help? Get the P Honda code diagnosed by a professional: Find a repair shop in your area.

Why is the Engine Light ON? Repair Importance Level: 2.This indicates there is a failure to have a low voltage output below 1. The O2 Sensor could be functioning improperly, or there could be a lack of continuity in the wiring to the ECU, or it is possible that power is not supplying sufficient enough voltage to the sensor. This sensor monitors oxygen levels in the exhaust stream. In order to check the O2 Oxygen Sensor Circuit High Voltage Bank 1, Sensor 2, the scanner will show the P code, which indicates the error, and the following should complete the checklist:.

Fouling would indicate a rich fuel mixture of more fuel than oxygen. This could cause fouling of the O2 sensor. Oil or coolant from an engine leak making its way into the exhaust system could be another cause for fouling. Check for damage to exhaust pipes and catalytic converter. Check wiring harness for melted wires especially near hot exhaust parts.

Do a visual check of the connections as well as using a Volt Ohm meter for wire connections. Another cause could be a damaged or clogged catalytic converter. A leaking fuel injector could possibly be another cause. The number one most common repair for this problem is replacing the O2 Sensor itself.

Another repair would be to replace the wiring or connection for Bank 1, Sensor 2. If the catalyst is the problem, replace the catalytic converter. Replace the fuel injector if it is leaking. After repairs have been made, clear stored codes from the ECU and test drive the vehicle between miles per hour for about two miles.

If the Oxygen O2 Sensor signal ever goes to a negative voltage, or in excess of one volt, this is indication that the sensor is bad.

p0138 civic

These inconsistent readings are often the reason to believe the circuit is losing voltage or ground into the O2 Sensor circuit. If the O2 Sensor body has a chalky appearance, this indicates lag between phases and should be replaced. Remember me. Table of Contents. Subscribe to our mailing list.Play Now. Check the "Possible Causes" listed above.

Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins. How much do you know about cars?

How to Replace an Oxygen Sensor in Your Car (Air Fuel Ratio Sensor)

Take the AutoCodes. Tech Notes What does this mean? The auto repair labor rates vary by location, your vehicle's make and model, and even your engine type.

When is the code detected? The P code is set when the Engine Control Module ECM detects that the rear O2 sensor signal voltage remains excessively high for an extended period of time.

For optimum catalyst operation, the air fuel mixture air-fuel ratio must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The HO2S generates a voltage between 0. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean.

If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. Get Access to Factory Service Manuals. Need more help? Get the P Honda Civic code diagnosed by a professional: Find a repair shop in your area. Why is the Engine Light ON? Comments Help us improve AutoCodes. Leave a comment below or tell us if the information above help you fix the code.The code is triggered when:. Typically, the only symptom of P is going to be the service engine soon light.

In some cases, there can be other symptoms as well. These symptoms include:. But, like anything that causes the service engine soon light to come on it is a good idea to have it fixed as soon as possible. A poor air fuel mixture going through the catalytic converter. Here are the most common issues that cause the P code in the Honda Civic. They are presented in order somewhat of most to least likely to cause the problem. It is possible to diagnose the P with a multimeter.

If the light comes on, even for a second, you know that you have a short circuit causing the P trouble code. Good luck finding whatever caused P in your Honda Civic.

Honda Civic P0138: Oxygen Sensor High Voltage (Bank 1 -Sensor 2)

If you have anything that you would like to add, please feel free to leave a comment below. The code is triggered when: The voltage at the sensor remains above threshold for 20 seconds or more Voltage to the sensor is to high wiring problem, think short Bad O2 sensor itself There are also some less likely problems that can cause P Bad Oxygen Sensor — The O2 sensor itself is one of the most likely reasons that P is triggering your service engine soon light.

See directly below. They are relatively affordable at Autozone or Amazon. Wiring Harness Issues — The wiring that goes to the front and rear oxygen sensors is very susceptible to damage. This is due to the fact that O2 sensors are under the chassis where they are subject to punishment from road debris, and they are subjected to a lot of exhaust heat. Damage to the Terminal — The terminal that the oxygen sensor connects to the plug is also relatively susceptible to damage.

Wrong O2 Sensor — If you are getting P after having recently replaced your Oxygen sensor, it may be that the replacement is wrong or bad.

Civic P Diagnosis It is possible to diagnose the P with a multimeter. Conclusion Good luck finding whatever caused P in your Honda Civic.