How severe is this DTC?

A shorted HO2S could cause very poor engine operation and various driving issues. A P2232 code should be classified as severe and rectified as quickly as possible.

What are some symptoms of the code?

Symptoms of a P2232 trouble code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illumination

What are some common causes of the code?

Causes of this code may include:

• Faulty oxygen sensor(s)
• Burned, chafed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the troubleshooting steps for P2232?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and reliable vehicle information source will be needed to accurately diagnose a P2232 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves to be intermittent. Then clear the codes and test drive the vehicle. One of two things will happen at this point. Either the P2232 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused the P2232 to store may need to worsen before an accurate diagnosis can be made. If the code resets, continue your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring schematics, and diagnostic flowcharts (related to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of wiring and connectors related to the HO2S. Replace any wiring that has been cut, burned, or damaged.

If the P2232 code continues to reset, start the engine. Let it reach normal operating temperature and idle (with transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and observe oxygen sensor input data on the data stream. Narrow the scope of the data stream to include only relevant data and you’ll get a faster response.

If the oxygen sensors are functioning normally, the voltage on pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. Post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively stable (compared to pre-cat sensors). HO2S that aren’t functioning properly should be considered faulty if the engine is in good operating condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to obtain live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will need replacement.

In most cases, you’ll rectify this code by replacing the HO2S in question but still complete your diagnosis.

How severe is this DTC?

A short-circuited HO2S could cause very poor engine performance and various driving issues. A P2233 code should be classified as severe and repaired as quickly as possible.

What are some symptoms of the code?

Symptoms of a P2233 trouble code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illumination

What are some common causes of the code?

Causes

of this code may include:

• Faulty oxygen sensor(s)
• Burned, rubbed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the troubleshooting steps for P2233?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and reliable vehicle information source will be needed to accurately diagnose a P2233 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves to be intermittent. Then clear the codes and test drive the vehicle. One of two things will happen at this point. Either the P2233 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused the P2233 to be stored may need to worsen before an accurate diagnosis can be made. If the code resets, continue your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring schematics, and diagnostic flowcharts (related to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of wiring and connectors related to the HO2S. Replace any wiring that has been cut, burned, or damaged.

If the P2233 code continues to reset, start the engine. Let it reach normal operating temperature and idle (with transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and monitor oxygen sensor input data on the data stream. Limit the scope of the data stream to include only relevant data and you’ll get a faster response.

If the oxygen sensors are functioning normally, the voltage on pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. Post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively stable (compared to pre-cat sensors). HO2S that are not functioning properly should be considered defective if the engine is in good operating condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to obtain live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will need replacement.

In most cases, you will fix this code by replacing the affected HO2S but still complete your diagnosis.

How severe is this DTC?

A shorted HO2S could cause very poor engine operation and various driving issues. A P2234 code should be classified as severe and rectified as quickly as possible.

What are some symptoms of the code?

Symptoms of a P2234 trouble code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illumination

What are some common causes of the code?

Causes of this code may include:

• Faulty oxygen sensor(s)
• Burned, chafed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the troubleshooting steps for P2234?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and reliable vehicle information source will be needed to accurately diagnose a P2234 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves intermittent. Then clear the codes and test drive the vehicle. One of two things will happen at this point. Either the P2234 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused P2234 to store may need to worsen before an accurate diagnosis can be made. If the code resets, continue your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring diagrams, and diagnostic flowcharts (related to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of wiring and connectors related to the HO2S. Replace any wiring that has been cut, burned, or damaged.

If P2234 continues to reset, start the engine. Let it reach normal operating temperature and idle (with transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and observe oxygen sensor input data on the data stream. Limit the scope of the data stream to include only relevant data and you’ll get faster response.

If the oxygen sensors are functioning normally, the voltage on pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. Post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively stable (compared to pre-cat sensors). HO2S that aren’t functioning properly should be considered faulty if the engine is in good operating condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to obtain live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will need replacement.

In most cases, you’ll rectify this code by replacing the HO2S in question but still complete your diagnosis.

How severe is this DTC?

A shorted HO2S could cause very poor engine operation and various driving issues. A P2235 code should be classified as severe and rectified as quickly as possible.

What are some symptoms of the code?

Symptoms of a P2235 trouble code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illumination

What are some common causes of the code?

Causes of this code may include:

• Faulty oxygen sensor(s)
• Burned, chafed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the P2235 troubleshooting steps?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and reliable vehicle information source will be needed to accurately diagnose a P2235 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves intermittent. Then clear the codes and test drive the vehicle. One of two things will happen at this point. Either the P2235 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused P2235 to store may need to worsen before an accurate diagnosis can be made. If the code resets, continue your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring diagrams, and diagnostic flowcharts (relevant to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of wiring and connectors related to the HO2S. Replace any wiring that has been cut, burned, or damaged.

If P2235 continues to reset, start the engine. Let it reach normal operating temperature and idle (with transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and observe oxygen sensor input data on the data stream. Limit the data stream scope to include only relevant data and you’ll get faster response.

If the oxygen sensors are functioning normally, the voltage on pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. Post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively stable (compared to pre-cat sensors). HO2S that aren’t functioning properly should be considered faulty if the engine is in good operating condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to obtain live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will need replacement.

In most cases, you’ll rectify this code by replacing the affected HO2S but still complete your diagnosis.

How severe is this DTC?

A shorted HO2S could cause very poor engine operation and various driving issues. A P2236 code should be classified as severe and fixed as soon as possible.

What are some of the symptoms of the code?

Symptoms of a P2236 trouble code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illumination

What are some common causes of the code?

Causes

of this code may include:

• Faulty oxygen sensor(s)
• Burned, rubbed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the troubleshooting steps for P2236?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and a reliable vehicle information source will be needed to accurately diagnose a P2236 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves intermittent. Then clear the codes and test drive the vehicle. One of two things will happen at this point. Either the P2236 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused P2236 to be stored may need to worsen before an accurate diagnosis can be made. If the code resets, continue your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring diagrams, and diagnostic flowcharts (related to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of wiring and connectors related to the HO2S. Replace wiring that has been cut, burned, or damaged.

If the P2236 code continues to reset, start the engine. Let it reach normal operating temperature and idle (with transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and observe oxygen sensor input data on the data stream. Limit the scope of the data stream to include only relevant data and you’ll get a faster response.

If the oxygen sensors are functioning normally, the voltage on pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. Post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively stable (compared to pre-cat sensors). HO2S that are not functioning properly should be considered faulty if the engine is in good operating condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to get live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will need replacement.

In most cases, you will fix this code by replacing the HO2S in question but still complete your diagnosis.

How severe is this DTC?

An HO2S with a control circuit issue could lead to very poor engine performance and various driving problems. A P2237 code should be classified as severe and fixed as soon as possible.

What are some symptoms of the code?

Symptoms of a P2237 trouble code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illuminated

What are some common causes of the code?

Causes

of this code may include:

• Faulty oxygen sensor(s)
• Burned, chafed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the troubleshooting steps for P2237?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and a reliable vehicle information source will be needed to accurately diagnose a P2237 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves to be intermittent. Then clear the codes and test drive the vehicle. One of two things will happen at this point. Either the P2237 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused P2237 to be stored may need to worsen before an accurate diagnosis can be made. If the code resets, continue your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring schematics, and diagnostic flowcharts (related to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of wiring and connectors related to the HO2S. Replace any wiring that has been cut, burned, or damaged.

Disconnect the HO2S in question and use the DVOM to check resistance between the positive current control circuit and ground circuits. If there is continuity, suspect a faulty HO2S.

If the P2237 code continues to reset, start the engine. Let it reach normal operating temperature and idle (with transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and observe oxygen sensor input data on the data stream. Limit the scope of the data stream to include only relevant data and you’ll get a faster response.

If the oxygen sensors are functioning normally, the voltage on pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. Post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively stable (compared to pre-cat sensors). HO2S that are not functioning properly should be considered faulty if the engine is in good operating condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to get live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will require HO2S replacement.

In most cases, you will fix this type of code by replacing the HO2S in question but still complete your diagnosis.

How severe is this DTC?

An HO2S with a control circuit issue could lead to very poor engine performance and various driving problems. A P2238 code should be classified as severe and fixed as soon as possible.

What are some of the symptoms of the code?

Symptoms of a P2238 trouble code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illumination

What are some common causes of the code?

Causes

of this code may include:

• Faulty oxygen sensor(s)
• Burned, rubbed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the troubleshooting steps for P2238?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and a reliable vehicle information source will be needed to accurately diagnose a P2238 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves to be intermittent. Then clear the codes and test drive the vehicle. One of two things will happen at this point. Either the P2238 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused the P2238 to be stored may need to worsen before an accurate diagnosis can be made. If the code resets, continue your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring schematics, and diagnostic flowcharts (related to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of the wiring and connectors related to the HO2S. Replace any wiring that has been cut, burned, or damaged.

Disconnect the HO2S in question and use the DVOM to check resistance between the positive current control circuit and ground circuits. If there is continuity, suspect a faulty HO2S.

If the P2238 code continues to reset, start the engine. Let it reach normal operating temperature and idle (with transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and observe oxygen sensor input data on the data stream. Limit the scope of the data stream to include only relevant data and you’ll get a faster response.

If the oxygen sensors are functioning normally, the voltage on pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. Post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively stable (compared to pre-cat sensors). HO2S that are not functioning properly should be considered faulty if the engine is in good operating condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to get live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will require HO2S replacement.

In most cases, you will fix this type of code by replacing the HO2S in question but still complete your diagnosis.

How severe is this DTC?

An HO2S with a control circuit issue could lead to very poor engine performance and various driving problems. A P2239 code should be classified as severe and fixed as soon as possible.

What are some of the symptoms of the code?

Symptoms of a P2239 trouble code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illumination

What are some common causes of the code?

Causes

of this code may include:

• Faulty oxygen sensor(s)
• Burned, rubbed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the troubleshooting steps for P2239?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source will be needed to accurately diagnose a P2239 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves to be intermittent. Then clear the codes and test the vehicle. One of two things will happen at this point. Either the P2239 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused the P2239 to be stored may need to worsen before an accurate diagnosis can be made. If the code resets, continue your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring schematics, and diagnostic flowcharts (related to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of the wiring and connectors related to the HO2S. Replace any wiring that has been cut, burned, or damaged.

Disconnect the HO2S in question and use the DVOM to check the resistance between the positive current control circuit and the ground circuits. If there is continuity, suspect a faulty HO2S.

If the P2239 code continues to reset, start the engine. Let it reach its normal operating temperature and idle (with the transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and observe the oxygen sensor input data on the data stream. Limit the scope of the data stream to include only relevant data, and you’ll get a faster response.

If the oxygen sensors are functioning normally, the voltage on the pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. The post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively stable (compared to the pre-cat sensors). HO2S that are not functioning correctly should be considered faulty if the engine is in good operating condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to obtain live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will require replacing the HO2S.

In most cases, you will fix this type of code by replacing the HO2S in question but still perform your diagnosis.

How severe is this DTC?

An HO2S with a control circuit issue could lead to very poor engine performance and various driving problems. A P2240 code should be classified as severe and fixed as soon as possible.

What are some of the symptoms of the code?

Symptoms of a P2240 fault code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illumination

What are some common causes of the code?

Causes of this code may include:

• Faulty oxygen sensor(s)
• Burned, rubbed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the troubleshooting steps for P2240?

A diagnostic scanner, digital volt/ohmmeter (DVOM), and a reliable vehicle information source will be needed to accurately diagnose a P2240 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves to be intermittent. Then clear the codes and test drive the vehicle. One of two things will happen at this point. Either the P2240 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused the P2240 to be stored may need to worsen before an accurate diagnosis can be made. If the code resets, continue your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring diagrams, and diagnostic flowcharts (related to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of the wiring and connectors related to the HO2S. Replace any wiring that has been cut, burned, or damaged.

Disconnect the HO2S in question and use the DVOM to check resistance between the positive current control circuit and ground circuits. If there is continuity, suspect a faulty HO2S.

If the P2240 code continues to reset, start the engine. Let it reach normal operating temperature and idle (with transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and observe oxygen sensor input data on the data stream. Limit the scope of the data stream to include only relevant data and you’ll get a faster response.

If the oxygen sensors are functioning normally, the voltage on pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. Post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively stable (compared to pre-cat sensors). HO2S that are not functioning properly should be considered faulty if the engine is in good operating condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to obtain live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will require HO2S replacement.

In most cases, you will fix this type of code by replacing the HO2S in question but still complete your diagnosis.

How severe is this DTC?

An HO2S with a control circuit issue could lead to very poor engine performance and various driving problems. A P2241 code should be classified as severe and fixed as soon as possible.

What are some of the symptoms of the code?

Symptoms of a P2241 fault code may include:

• Reduced fuel efficiency
• Decreased engine performance
• Stored misfire codes or lean/rich exhaust codes
• Service engine soon light illumination

What are some common causes of the code?

Causes of this code may include:

• Faulty oxygen sensor(s)
• Burned, chafed, broken, or disconnected wiring and/or connectors
• PCM programming error or faulty PCM

What are the troubleshooting steps for P2241?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source will be needed to accurately diagnose a P2241 code.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and relevant freeze frame data. You’ll want to note this information in case the code proves to be intermittent. Then, clear the codes and test-drive the vehicle. One of two things will happen at this point. Either the P2241 code will reset, or the PCM will enter readiness mode.

If the code is intermittent and the PCM enters readiness mode, it may prove more difficult to diagnose. The conditions that caused the P2241 to be stored may need to worsen before an accurate diagnosis can be made. If the code resets, continue with your diagnosis.

Connector face views, connector pinout diagrams, component location diagrams, wiring diagrams, and diagnostic flowcharts (related to the specific code and vehicle) can be found using your vehicle information source.

Perform a visual inspection of the wiring and connectors related to the HO2S. Replace any wiring that has been cut, burned, or damaged.

Disconnect the HO2S in question and use the DVOM to check for continuity between the positive current control circuit and ground circuits. If there is continuity, suspect a faulty HO2S.

If the P2241 code continues to reset, start the engine. Let it reach its normal operating temperature and idle (with the transmission in neutral or park). Connect the scanner to the vehicle’s diagnostic port and observe the oxygen sensor input data on the data stream. Narrow the scope of the data stream to include only relevant data, and you’ll get a faster response.

If the oxygen sensors are functioning normally, the voltage on the pre-cat oxygen sensors will continuously cycle between 1 and 900 millivolts once the PCM enters closed-loop operation. The post-cat sensors will also cycle between 1 and 900 millivolts, but they will stabilize at a certain point and remain relatively steady (compared to the pre-cat sensors). HO2S that are not operating correctly should be considered faulty if the engine is in good running condition.

If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to obtain live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short circuit that will require replacing the HO2S.

In most cases, you will fix this type of code by replacing the HO2S in question but still perform your diagnosis.