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P2238 OBD-II Trouble Code: O2 Sensor Positive Current Control Circuit Low Bank 1 Sensor 1

Check Engine Light

What the P2238 code means?

P2238 is an OBD-II generic code for the engine control module (ECM) detecting the O2 sensor for bank 1 sensor 1 has a short circuit for the heater control circuit of the O2 sensor.

What causes the P2238 code?

  • The O2 sensor has an short circuit in the heater circuit internal of the sensor.

  • The wiring or connector for the O2 sensor has an short circuit or corrosion in the connections.

  • The heater power relay is shorted to the O2 sensor circuit ground.

What are the symptoms of the P2238 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 ECM will go into open loop fuel control on some vehicles and not failure mode.

  • The engine may have different drivability symptoms depending on the manufacture failure mode controls or open loop fuel control.

How does a mechanic diagnose the P2238 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 circuits in the sensor and relay.

  • 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 P2238 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

  • Replacing all the O2 sensors when the short is in the wiring

How serious is the P2238 code?

Code P2238 is a code indicating the O2 sensor heater circuit is shorted causing the circuit voltage control to be low. This will cause the fuel feedback control to not work and the ECM to put the engine into failure mode or open loop fuel control. This will also cause the vehicle to fail emissions testing.

What repairs can fix the P2238 code?

  • Replace the O2 sensor for an short circuit in the heater circuit.

  • Repair the wiring connector or wiring to the O2 sensor for shorts.

  • Replace the power relay for the heater circuit due to a burned out or shorted circuit that the pinpoint test indicated.

  • Replace the ECM if shorted harness or sensor damaged the ECM.

Additional comments for consideration regarding the P2238 code

Code P2238 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 or the relay to burn out. Note this if the fuse keeps blowing out when it is replaced. Check all the sensors for intact coverings.

Need help with a P2238 code?

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