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.