The P2231 code indicates that the On‑Board Diagnostics system has detected a short in the heater circuit of the bank 1 oxygen sensor 1 (the upstream sensor). This means the sensor’s heater element is drawing more current than normal, which can cause the sensor to misread air‑fuel mixture and trigger the code.
A short in the sensor’s heater coil or wiring causes excess current draw, triggering the code.
A damaged or frayed wire that contacts metal or a short to ground can create a shorted heater circuit.
Loose or corroded pins in the sensor plug can lead to intermittent shorts in the heater circuit.
A poor ground connection on the ECM side can appear as a heater short but is less common.
In rare cases, incorrect sensor data can be reported as a short, but this is uncommon and usually ruled out after hardware checks.
Replacing the PCM is rarely necessary. The code almost always points to a shorted heater element, damaged wiring, or a connector issue. The PCM should be considered only after all hardware has been inspected and ruled out.
Yes, a shorted heater circuit can cause the oxygen sensor to provide incorrect data to the engine control unit, leading to a rich air‑fuel mixture and increased emissions until the code is cleared.
Heater elements can fail after many thousands of miles or when exposed to heat, vibration, or corrosion, but exact lifespan varies with driving conditions and maintenance.