P2240 indicates that the engine control module has detected an open circuit in the positive current (heater) control circuit of the oxygen sensor located on bank 2, sensor 1 – the upstream sensor before the catalytic converter. The heater is used to bring the sensor to operating temperature quickly; when the circuit is open, the ECM cannot monitor the heater’s operation and sets the code. This can affect fuel mixture control and increase exhaust emissions.
The internal heater element inside the sensor can fail, creating an open circuit that prevents proper heating.
Broken, corroded, or disconnected wires in the sensor harness, or a damaged connector, can interrupt the heater circuit.
If the fuse that supplies power to the heater circuit is open, the sensor will not receive voltage.
A weak ground or insufficient reference voltage can prevent the heater driver from completing the circuit.
In very few cases the engine computer’s heater driver may fail, but this should be ruled out only after all external components are verified.
No. While the PCM controls the heater circuit, it fails far less often than the sensor, wiring, or a blown fuse. PCM replacement should be a last resort after all other possibilities are confirmed.
You can drive, but the vehicle may experience reduced fuel economy and higher emissions, and the Check Engine light will stay on. It is advisable to diagnose and repair the issue promptly.
It typically does not cause immediate engine damage, but prolonged operation with an open O2 heater circuit can lead to poorer fuel control and potentially higher exhaust temperatures, which over time may affect the catalytic converter.
The most common repairs involve fixing damaged wiring, replacing the faulty O2 sensor, or addressing a blown fuse. PCM replacement is only necessary in rare cases.