P2251 - O2 SENSOR NEGATIVE CURRENT CONTROL CIRCUIT / OPEN BANK 1 SENSOR 1

To monitor the oxygen content in the exhaust of each engine bank and check the effectiveness of the catalytic converter (TWC), the car’s computer uses the data provided by the Oxygen (O2) Sensors. Each of these sensors is threaded into an exhaust pipe or manifold. In this way, the exhaust gases that are expelled from the combustion chamber pass over them.

The PCM monitors the negative current driver circuit of the O2 Sensor constantly, and if it fails to control the current, losing the voltage return through the corresponding wire, it recognizes this condition as an open circuit, so it will set the fault code P2251 OBD2.

• Check Engine lamp ON
• Higher fuel consumption.
• Motor power is reduced.
• Other misfire codes were stored.

Reasons to set the P2251 OBDII DTC P2251:

• Wires or connectors leading to the Oxygen Sensor may be burned, worn, or corroded.
• The O2 sensor may be faulty.

To troubleshoot the P2251 OBD2 diagnostic code, try this:

• Check the cables and connectors leading to the Oxygen (O2) Pay attention to the wires as they are exposed to high temperatures, resulting in burns to the wires. Besides, look at the terminals of the connectors because they usually have corrosion. Repair or replace any of these for possible defects.
• Check the resistance between the negative current control circuit and a voltage circuit with a digital volt-ohm meter. If continuity is found, the O2 Sensor may be faulty.
• To check for proper operation of the Oxygen Sensor, start the engine and wait until it reaches the operating temperature. Then, connect a scanner to the diagnostic port, and watch the input data from the O2 Sensor. You should observe a continuously cycling voltage ranging from 1 to 900 millivolts after the PCM goes into a closed loop. If not, the O2 Sensor can be considered defective, replace it.