P0051 - OXYGEN (A/F) SENSOR HEATER CONTROL CIRCUIT LOW (BANK 2 SENSOR 1)

Diagnostic code P0051 OBD2 refers to Oxygen Sensor (O2) number 1 which is located in bank number 2 opposite the 3-way Catalytic Converter (TWC).  It should be noted that there is an Oxygen Sensor which is located on the back of the Three Way Catalyst (TWC) and corresponds to O2 number 2 in bank number 2.

The Oxygen Sensors (O2) detect the portion of oxygen found in the exhaust gases and compare them to the outside of the air. This information is sent to the Powertrain Control Module (PCM) who with this information fit the air-fuel ratio.

If the exhaust gas temperature is low, the function of the Oxygen Sensor is affected, which is why these sensors include a heating element, which is hastied to make the Oxygen Sensor readings more effective.

When this DTC code is set it indicates that the resistance of the heating element circuit is below normal. Generally, this resistance level is lower than 0.8 A for the code to be set.

• MIL light is on.
• Fuel economy is poor.

The P0051 code OBDII can be set because:

• Oxygen (O2) sensor heating element circuit wires may be defective and cause a short circuit.
• Bad electrical connection in the heating element circuit.
• Oxygen Sensor (O2) number 1 defective.

Before the fault code P0051 you can do the following for its repair:

• Perform a thorough inspection of the wiring and its respective connectors leading to the Oxygen Sensor(O2). Also check the relay or fuse in case your vehicle is equipped with one of them. Repair or replace any of these components in case they have problems.
• Use a digital meter and ascertain for 12 volts in the heating element circuit. To do this you must disconnect the sensor and check the voltage in the connector of the wiring.
• Verify the ground circuit, make sure there is continuity.
• Calculate the resistance of the heated element circuit. All these readings should be compared to factory specifications. If they do not match, make repairs.
• Change Oxygen (O2) Sensor 1.