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P0151 is a diagnostic trouble code (DTC) for "O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
P0151 is the OBD-II generic code indicating the O2 sensor for bank 2 sensor 1 fails to increase the voltage output above .21 volts, indicating excessive oxygen in the exhaust.
The Engine Control Module (ECM) sees the voltage of the O2 sensor for bank 2 sensor 1 below .21 volts when the ECM has commanded the fuel to a targeted rich condition on that bank of the engine.
Exhaust leaks before the sensor introduce excessive oxygen into the exhaust, causing the O2 sensor to read excessive oxygen, and the ECM to run rich.
The O2 sensor low voltage causes the ECM to enrichen the mixture into the engine.
The Check Engine Light will be illuminated.
You may have exhaust leaks before or near the O2 sensor in question. The exhaust leaks may be more when the engine is cold, and decrease as the engine warms up.
Scans codes and documents freeze frame data then clear codes to verify failure
Monitors O2 sensor data to see if the voltage is switching back and forth between low and high at a fast rate compared to other sensors
Checks the O2 sensor wiring and the harness connections for any corrosion in the connections
Checks the O2 sensor for any physical damage or fluid contamination; repairs any leaks before replacing O2 sensor
Checks for exhaust leaks before the sensor, repairs leaks, and retests sensor
Follow these simple guidelines to prevent misdiagnosis:
Repair any exhaust leaks before the sensor to prevent excess oxygen getting into the exhaust stream, causing the low voltage readings.
Repair oil or coolant leaks that can contaminate or can foul the sensors.
The voltage output from the O2 sensor may be due to exhaust leaks causing the O2 sensors to give low output voltages indicating excessive oxygen in the exhaust stream.
The ECM cannot control the fuel to air ratio of the engine if the O2 sensor is malfunctioning. This will cause poor fuel mileage, and the excessive fuel will foul spark plugs over time..
Replacing the O2 sensor for bank 2 sensor 1 if all tests indicate a failed sensor
Repairing or replacing the wiring or connection to the O2 sensor for bank 2 sensor 1
Repairing exhaust leaks before the sensor that introduce excessive oxygen into the exhaust
The O2 sensor circuit for bank 2 sensor 1 is used to give a voltage feedback to the ECM showing how much oxygen is in the exhaust stream to help the engine control the air to fuel ratio. The low voltage condition indicates excessive oxygen in the exhaust.
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