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P2243 OBD-II Trouble Code: O2 Sensor Reference Voltage Circuit Open Bank 1 Sensor 1

Check Engine Light

What the P2243 code means?

P2243 is an OBD-II generic code for the engine control module (ECM) detecting the O2 sensor for bank 1 sensor 1 having an open circuit for the reference voltage to the O2 sensor.

What causes the P2243 code?

  • The O2 sensor has an open circuit in the reference voltage circuit to the sensor or internal of the sensor.

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

What are the symptoms of the P2243 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 like a lean surge, hesitation on acceleration, or a rough running engine.

How does a mechanic diagnose the P2243 code?

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

  • Checks the O2 sensor reference voltage circuit compared to the other O2 sensors to be the same reference voltage input.

  • Checks the O2 reference voltage circuit for open circuits in the sensor connector.

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

  • Checks the wiring harness for open circuits from the O2 sensor to the ECM in the reference voltage signal from the ECM.

Common mistakes when diagnosing the P2243 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 reference voltage from the ECM before replacing the O2 sensor

  • Replacing all the O2 sensors when the problem is in the wiring harness

How serious is the P2243 code?

Code P2243 is a code indicating the O2 sensor reference voltage to the sensor is open and this will render the O2 sensor signal return inoperative and cause the ECM to go into open loop fuel control and turn on the Check Engine Light. This will also cause the vehicle to fail any emissions testing.

What repairs can fix the P2243 code?

  • Replace the O2 sensor for an open circuit in the reference voltage circuit.

  • Repair the wiring connector or wiring to the O2 sensor for open or corroded connections.

  • Replace the ECM if the reference voltage signal to the sensor is open in the ECM.

Additional comments for consideration regarding the P2243 code

Code P2243 is caused most commonly from an internal failure of the reference voltage 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 circuit and blow the O2 sensor reference circuit in the ECM.

Need help with a P2243 code?

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The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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