P2237 Code: O₂ Sensor Positive Current Control Circuit Open (Bank 1, Sensor 1)
The P2237 trouble code indicates that the PCM has detected an open circuit or fault in the positive current control circuit for the upstream oxygen sensor (Bank 1, Sensor 1). This can lead to poor engine performance, reduced fuel efficiency, and increased emissions.
What Does the P2237 Code Mean?
On Ford and many other makes, Bank 1 Sensor 1 is located before the catalytic converter. It monitors oxygen levels in the exhaust and sends data to the PCM for precise fuel control. If the sensor’s positive current control circuit is open or faulty, the PCM cannot adjust the air-fuel ratio properly, triggering the P2237 code.
Common Symptoms of P2237
- Check Engine Light illuminated
- Reduced engine performance
- Poor fuel economy
- Failed emissions test
Possible Causes
- Failed O₂ sensor (Bank 1, Sensor 1)
- Open or damaged wiring harness
- Corroded or loose electrical connectors
- PCM fault (less common)
How to Diagnose and Fix P2237
- Use a professional OBD-II scanner like the iCarsoft CR MAX BT to confirm the P2237 code.
- Visually inspect the O₂ sensor wiring and connector for damage.
- Perform a continuity and voltage test on the control circuit.
- If wiring and connectors are fine, replace the O₂ sensor with an OEM-quality part.
- Clear the code and test drive to ensure it does not return.
FAQ
Is P2237 serious?
While you can still drive with this code, ignoring it can reduce fuel efficiency, harm catalytic converters, and increase emissions.
Will replacing the O₂ sensor fix P2237?
Often yes, but first check the wiring and connectors to avoid replacing a good sensor unnecessarily.
Can I fix P2237 myself?
If you have basic automotive repair skills and the right scan tool, you can diagnose and repair this yourself.
