P2237 OBD-II Trouble Code: O2 Sensor Positive Current Control Circuit/Open Bank 1 Sensor 1

Check Engine Light

What the P2237 code means

P2237 is an OBD-II generic code for the engine control module (ECM) detecting the O2 sensor for bank 1 sensor 1 and has an open circuit for the heater control circuit of the O2 sensor. The ECM tests the sensor circuit after the engine is warmed up.

What causes the P2237 code?

  • The O2 sensor has an open circuit in the heater circuit internal of the sensor.
  • The heater power relay is shorted to the O2 sensor circuit ground.
  • The wiring or connector for the O2 sensor has an open circuit or corrosion in the connections.

What are the symptoms of the P2237 code?

  • The Check Engine light will be illuminated and the code is set in ECM memory as a fault.

  • The ECM will turn off the Check Engine light if three drive cycles pass without another failure.

  • The ECM may go into failure mode fuel control on most manufacturer vehicles.

  • The engine may have different drivability symptoms depending on the manufacture failure mode controls.

How does a mechanic diagnose the P2237 code?

  • Scans for codes and documents the code in the ECM and looks at the freeze frame data for failure.

  • Checks the O2 sensor heater circuit compared to the other O2 sensors to be the same voltage input and control voltages.

  • Checks the O2 heater circuit for open or short circuit in the sensor.

  • Tests the O2 sensor wiring is not shorted to the power relay or ground.

  • Checks the wiring harness for shorts or open circuits from the O2 sensor to the ECM.

Common mistakes when diagnosing the P2237 code?

  • Clearing ECM memory codes before checking the freeze frame data for the main failure problem, so the failure may be duplicated and repaired

  • Failing to verify the failure before replacing the O2 sensor

How serious is the P2237 code?

Code P2237 is a code indicating the O2 sensor heater circuit is open or shorted causing the circuit voltage control to be open. This will cause the fuel feedback control to not work and the ECM to put the engine into failure mode. This will also cause the vehicle to fail emissions testing.

What repairs can fix the P2237 code?

  • Replace the O2 sensor for an open circuit in the heater circuit.
  • Repair the wiring connector or wiring to the O2 sensor.
  • Replace the power relay for the heater circuit due to a burned out or shorted circuit that the pinpoint test indicated.

Additional comments for consideration regarding the P2237 code

Code P2237 is caused most commonly from an internal failure of the heater circuit inside the O2 sensor. The O2 sensor wiring cover is also a vent on some O2 sensors and if the cover is cut or removed then the sensor can get water into the back side of the sensor and cause it to short out the heater circuit and blow the O2 sensor heater circuit fuse. Note this if the fuse keeps blowing out when it is replaced. Check all the sensors for intact coverings.

Need help with a P2237 code?

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