<ul> <li><b>Engine Light ON</b>: The 'Check Engine' or 'Service Engine Soon' warning light illuminates. This is a common indicator of an issue with the O2 sensor negative current control circuit in Bank 2 Sensor 1. Potential causes include a faulty O2 sensor, damaged wiring, or a malfunctioning Engine Control Module (ECM).</li> </ul>

<ul><li>The front oxygen sensor on Bank 2 may be faulty, leading to incorrect readings and triggering the error code.</li><li>An open or shorted harness in the front oxygen sensor Bank 2 can disrupt the signal, causing the control circuit to register low.</li><li>Poor electrical connections in the front oxygen sensor Bank 2 circuit can result in intermittent or weak signals, affecting the sensor's performance.</li></ul>

<ul> <li><b>Retrieve Codes and Freeze Frame Data</b>: Connect the diagnostic scanner to the vehicle's diagnostic port. Retrieve all stored codes and pertinent freeze frame data. Write this information down for reference.</li> <li><b>Clear Codes and Test Drive</b>: Clear the codes and test drive the vehicle. Observe if the code P2255 is reset or if the PCM enters readiness mode.</li> <li><b>Visual Inspection</b>: Perform a visual inspection of the HO2S related wiring and connectors. Replace any wiring that is cut, burned, or damaged.</li> <li><b>Check Resistance</b>: Unplug the HO2S in question. Use a DVOM to check resistance between the negative current control circuit and any voltage circuits. If there is continuity, suspect a defective HO2S.</li> <li><b>Observe Oxygen Sensor Data</b>: Start the engine and allow it to reach normal operating temperature. Connect the scanner and observe oxygen sensor input data. Pre-cat sensors should cycle between 1 and 900-millivolts. Post-cat sensors should also cycle but remain relatively stable.</li> <li><b>Check HO2S Voltage</b>: If the HO2S displays battery voltage or no voltage on the scanner data stream, use the DVOM to obtain live data from the HO2S connector. If the output data remains the same, suspect an internal HO2S short.</li> <li><b>Replace HO2S if Necessary</b>: If the HO2S is found to be defective based on the above tests, replace the HO2S in question.</li></ul>

<p>The DTC code P2255 indicates an issue with the O2 Sensor Negative Current Control Circuit Low for Bank 2 Sensor 1. This can lead to improper air-fuel mixture, affecting engine performance and fuel efficiency.</p><ul><li><b>Immediate Actions:</b> Inspect and possibly replace the O2 sensor.</li><li><b>Potential Risks:</b> Delayed repair can result in increased emissions and potential damage to the catalytic converter.</li></ul>