P0151 OBD-II Trouble Code: O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE P0151 DIAGNOSTIC Get a fair and transparent estimate upfront
Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0151 code

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 for $70.00. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $30.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$70.00$30.00
Toyota$70.00$30.00
BMW$70.00$30.00
SCHEDULE P0151 DIAGNOSTIC Get a fair and transparent estimate upfront

check engine light logo

P0151 code definition

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

What the P0151 code means

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.

What causes the P0151 code?

  • 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.

What are the symptoms of the P0151 code?

  • 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.

How does a mechanic diagnose the P0151 code?

  • 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

Common mistakes when diagnosing the P0151 code

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.

How serious is the P0151 code?

  • 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..

What repairs can fix the P0151 code?

  • 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

Additional comments for consideration regarding the P0151 code

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.

Need help with a P0151 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

P0151
trouble codes
Check Engine Light

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE P0151 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.5/5

Number of Reviews

3,484

Rating Summary
3,176
153
40
23
92
3,176
153
40
23
92

Richard

10 years of experience
415 reviews
Richard
10 years of experience
This is the second time I’ve had Richard work on my car. He always does an outstanding job and is quick, knowledgeable and professional. Highly recommended!!
2012 DODGE CHALLENGER - CHECK ENGINE LIGHT IS ON - LAS VEGAS, NEVADA

Michael

13 years of experience
372 reviews
Michael
13 years of experience
Mike was an absolute professional when he arrived. He walked me thru the whole process of my repairs and also made good recommendations for preventive issues. His mechanical knowledge and good customer services was a breath of air and greatly appreciated :-)
2007 CHEVROLET AVALANCHE - CHECK ENGINE LIGHT IS ON INSPECTION - MARIETTA, GEORGIA

Rodrigo

10 years of experience
85 reviews
Rodrigo
10 years of experience
Rodrigo was exactly on time, very professional and friendly. He assessed my car, let me know the exact problem when a previous mechanic from a shop in my area was unable to. I felt he was very honest and sincere letting me know the level of urgency that I deal with the issue. Absolutely no pressure. I will absolutely use Rodrigo the next time I need anything to do with my car and will tell everyone about him. This is such a great service, I will never go to another mechanic again. It is so convenient. I couldn’t be happier. :)
2013 SMART FORTWO - CHECK ENGINE LIGHT IS ON - LAS VEGAS, NEVADA

Ricardo

8 years of experience
223 reviews
Ricardo
8 years of experience
Great service and was very helpful on what maintenance my vehicle needed and what to expect in the future. Would definitely recommend to anyone and will.
2004 MITSUBISHI LANCER - CHECK ENGINE LIGHT IS ON - LOS ANGELES, CALIFORNIA

More related articles

How to Get a Louisiana Driver's Permit
s licensing program. The first step in this program is to obtain...
P2422 OBD-II Trouble Code: Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed
Diagnostic Trouble Code (DTC): P2422 P2422 code definition Evaporative Emissions Control System (EVAP)...
Auto Safety Tips
Driving is more than a way to get from point A to point B. Owning and driving a car can also be a highly enjoyable experience. Whether a person is driving...

Related questions

Q: I have codes P0151, P0171, and P0174. I have changed out my O2 sensor, but now I have all these codes

Hey there. The codes you have downloaded simply relate to malfunctions in the "engine management system." It appears codes were set for oxygen sensor voltage out-of-range, possible EGR (exhaust gas recirculation) problems such as a blockage, and a generic code...

Q: Engine light on. P000B Code

Hello. When this code comes up it is because the computer is not detecting that the camshaft is moving as it should when the variable valve timing system is functioning. This can be caused by a number of things. It...

Q: Q: My check engine light is on

Hi, thanks for writing in. If you have a check engine light on for a problem, then the computer may respond by increasing the cooling fan speeds if it see problems with the cooling system sensors. I suggest having the...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1-800-701-6230 · hi@yourmechanic.com