The O2 sensor monitors the level of oxygen that goes into the engine. When the sensor is damaged, the Powertrain Control Module (PCM) detects the problem and throws related codes. A damaged O2 sensor will not affect the drivability of your vehicle. However, it is recommended to fix it on time.
If the O2 sensor has been changed, the sensor needs to be reset, and can be done in several ways like disconnecting the O2 sensor to force the PCM to relearn the new sensor or resetting the O2 sensor using OBD II Scanner.
Personally, I have had the O2 sensor of my car damaged. Although I could still drive, my vehicle checked the engine light was on, and its PCM threw a series of disturbing codes. After changing the sensor, I reset the sensor using an OBD-2 scan tool and drove my car around my block. It cleared the code and reset the CEL.
How To Reset an O2 Sensor?
There are several ways to reset your vehicle’s O2 sensor, and it will depend on the vehicle’s brand and model. Reset your vehicle’s O2 sensor by disconnecting and allowing it to idle. Also, reset using the O2 sensor fuse or an OBD II scan tool to reset the error.
This article looks at three methods to safely reset your O2 sensor.
1. Disconnecting O2 sensor
Firstly, you can reset the O2 sensor by disconnecting the sensor and forcing the Powertrain Control Module (PCM) to relearn the newly installed O2 sensor.
Locate all O2 sensors in the vehicle. Note the number of sensors will depend on your vehicle’s model, year, and brand. Modern cars have at least 4 of these sensors. One is usually located before the catalytic converter, while the others are on the exhaust manifold. Consult your vehicle manual to find out where the O2 sensor lies in your car.
Once the O2 sensor has been disconnected, start the engine and allow it to idle for some minutes. It should reset the sensor. Turn off and start the ignition twice within 15 to 30 seconds intervals between each start. It will force the PCM to re-adapt to the O2 sensors.
Also Read: What Happens If You Remove O2 Sensor?
2. Disconnect the ECU Fuse
Reset the O2 sensor by disconnecting the ECU fuse. Locate the ECU fuse within the car. Check your vehicle manual to accurately describe where the O2 sensor fuse lies. After locating the fuse, pull it out and then switch the vehicle to start without cranking the engine.
Leave your vehicle in the position for about 5 minutes and then reinsert the fuse. The check engine light will blink, then go on to switch the ignition off. At this point, your ECU reset, and so is your O2 sensor.
3. Reset Using an OBD II scanner
Finally, reset the sensor using an OBD II scanner. You should get a quality OBD II scanner and connect it to your vehicle. The connection is usually found under the dashboard under the steering wheel.
Navigate the scanner until you find the control module OBD, select DC memory, and proceed to clear. Also, select basic settings, and reset the oxygen sensor learned to value.
How Long Does It Take for a New O2 Sensor to Reset?
The ECU will reset the sensor after about 2 consecutive drive cycles. Many people need to learn this, but when you install a new O2 sensor, it doesn’t reset the O2 sensor immediately and the ECU need some time to relearn the sensor.
Typically, the flow of resetting an O2 sensor will be as follow: Before installing a new O2 sensor, the PCM detected a problem with the O2 sensor, which made it throw codes related to a failed O2 sensor. The code is stored until the PCM detects that the problem has been fixed.
When you replace the O2 sensors, the PCM does not just reset the O2 sensor error. A series of events has to occur for the code to be properly cleared. Some people opt to clear the ECM using a scan tool or other methods, which is good as long as the underlying problem has been solved; if not, the code will return.
However, if you are patient enough with about two to three trips, the PCM can detect that the O2 sensor has been changed and the problem is solved.
Will Disconnecting Battery Reset O2 Sensor?
Disconnecting may or may not reset the O2 sensor of your vehicle. Whether or not the O2 will reset the battery is connected depends on what model and brand of vehicle you are using. Many modern vehicles’ O2 sensors will not reset after your battery has been disconnected, while older vehicles just might.
The O2 sensor is an electronic device connected to the ECM (which is also an electronic device). Both depend on electric current to function, and the PCM depends on the current to store data. By disconnecting the battery, these components cut away from their power source. If you leave them in that situation for some time, they will drain the all-electric current.
When the PCM is completely drained of electric current, all data stored in it will automatically be cleared up. The O2 sensor will be reset, along with other major parts of the vehicle connected to the PCM.
However, this is only sometimes the case with all vehicles. Some vehicles are built to ensure that the ECM and other parts of the vehicle do not lose electric current this is why they use auxiliary batteries. Many of these vehicles’ electric parts rely on the auxiliary battery for power, and disconnecting the main battery will not affect them.
How To Turn Off Check Engine Light on O2 Sensor?
There are many ways to reset the check engine light and make it go away. Some methods may require tools, while others may require you to turn the engine off and on or disconnect the battery. They include:
- Drive a few miles. After replacing the damaged sensor it may take the ECU some time to recognize the new sensor. Often, taking a trip or two should fix the problem. If it doesn’t, there may be more issues wrong with the car, and you should get a proper diagnosis.
- Switch the engine on and off a couple of times. In the third instance of doing this, the engine will automatically reset the trouble codes. You should know this method will only work for some vehicles, but it’s worth the try.
- Clear the error code with an OBD II reader. After replacing the damaged O2 sensor, plug the OBD II scanner into your vehicle and clear the error code. It should stop the CEL from illuminating. This method is one of the most accurate and reliable ways to clear errors and warning lights in your vehicle.
Q: Why Is My Check Engine Light (CEL) Still on After Changing the O2 Sensor?
The Check engine light may take a while to turn off as the PCM has yet to detect the replaced O2 sensor. Driving a couple of miles may reset the check engine light.
If the light is still persistent, there may be other underlying issues in the car. For instance, during the O2 sensor replacement, the catalytic converter could get damaged. Also, the wiring harness around the sensor may be corroded, triggering the CEL to illuminate. Replacing the damaged catalytic converter and checking the wiring may remedy the check engine light.
Q: Will an O2 Sensor Code Clear Itself?
When you install a new sensor or the problem related to the sensor has been solved, your vehicle’s computer system will automatically clear all error codes and warning lights triggered by the faulty sensor. Technically speaking, the sensor cannot reset itself, but the PCM or ECM is the component that clears it automatically.
Q: Should I Disconnect the Battery When Changing the O2 Sensor?
Before connecting the O2 sensor, you must disconnect the battery first. Connecting the O2 sensor while the battery is connected could damage the fuse, circuit, and even the new O2 sensor. A surge can occur while installing the new sensor, which could instantly damage it.
Q: Can Spark Plugs Cause O2 Sensor Code?
A bad spark plug can trigger an O2 sensor code. Bad spark plugs can result in an engine misfiring, which could throw lots of code in the vehicle computing system. Engine misfires caused by bad plugs cause excess oxygen to escape into the engine due to lack of combustion. The ECU detects the problem and throws a code.