Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. P0157 OBD-II Trouble Code: 02 Sensor Circuit Low Voltage (Bank 2 Sensor 2)

P0157 OBD-II Trouble Code: 02 Sensor Circuit Low Voltage (Bank 2 Sensor 2)

Check Engine Light

P0157 code definition

Oxygen Sensor Circuit Low Voltage (Bank 2 Sensor 2)

What the P0157 code means

The oxygen sensor that trouble code P0157 refers to, is located in the rear of the exhaust and behind the catalytic converter. It’s main function is to regulate the amount of oxygen that comes from the catalytic converter. A lean mixture of oxygen and gas means that there is too much oxygen in the exhaust. A rich mixture of oxygen and gas means that there is not enough oxygen in the exhaust.

Neither a lean mixture or rich mixture is good for the catalytic converter and both can cause premature failure of the catalytic converter. The oxygen sensor switches back and forth from low voltage (lean) to high voltage (rich). When this code is stored by the power control module (PCM), it means that the oxygen sensor has remained at a low voltage for too long.

What causes the P0157 code?

  • Faulty oxygen sensor (bank 2 sensor 2)
  • Insufficient fuel pressure
  • False reading of the oxygen sensor as a result of holes in the exhaust
  • Corrosion of the rear oxygen sensor’s connector
  • Fuel or coolant leaks on the rear oxygen sensor
  • Broken, shorted or exposed wires
  • Malfunction of the engine coolant temperature sensor
  • Defective power control module (PCM)
  • Update required for power control module (PCM)

What are the symptoms of the P0157 code?

  • Increase in fuel consumption
  • Check Engine Light is on
  • Engine runs rough or idles poorly
  • In some rare cases, there will be no symptoms noticed by the driver.

How does a mechanic diagnose the P0157 code?

  • Collects trouble code and views freeze frame data from the OBD-II scanner.

  • Also uses scan tool to monitor oxygen sensor voltage to see if it is switching properly.

  • If an engine coolant temperature sensor trouble code is present as well, view its live data to see if it is working properly.

  • Checks fuel pressure with fuel pressure gauge. Proper fuel pressure should be at 40 psi.

  • Inspects the exhaust for air leaks in the manifold and pipes.

  • Inspects the rear oxygen sensor wires for shorts, breaks or exposure.

  • The computer may need to be updated at the dealer.

  • Advance diagnosis may also be necessary to determine if there is a problem with the Primary Control Module (PCM).

Common mistakes when diagnosing the P0157 code

  • Replacing the oxygen sensor without confirming it is bad
  • Not inspecting the condition of the oxygen sensor wires
  • Not being able to inspect the condition of the exhaust

How serious is the P0157 code?

The P0157 trouble code is considered moderately serious. It can cause drivability issues and has the potential of causing the car to stall out. If not addressed, damage to the catalytic converter can be done over time, which will be expensive to fix. It is recommended to have this problem addressed as soon as possible.

What repairs can fix the P0157 code?

  • Replacing the rear oxygen sensor
  • Repairing of broken circuitry or shorted wires going to the oxygen sensor
  • If the fuel pressure is abnormal, repairing the cause of the abnormality
  • Repairing the engine coolant temperature sensor if it is faulty
  • Replacing the power control module (PCM) or having it updated, if necessary

Additional comments for consideration regarding the P0157 code

If the oxygen sensor has ceased up in the exhaust pipe, which is common, specialty tools will be required. An oxygen sensor set will make it easier to reach an oxygen sensor that is positioned awkwardly, and a propane torch is used as a heating element to assist in the removal.

Need help with a P0157 code?

YourMechanic offers certified 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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Shutterstock.com Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....
Veteran and Military Driver Laws and Benefits in Idaho
The state of Idaho offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch in the...
Veteran and Military Driver Laws and Benefits in New Mexico
The state of New Mexico offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch...


Related questions

Q: Trouble running when the engine warms up, dash lights on - 2007 Subaru B9 Tribeca

The P0137/P0157 codes indicate the "rear" (behind the catalytic converters) oxygen sensors are not functioning properly. In turn, they are signaling (incorrectly) for more fuel, which is causing the P0172/P0175 over-rich codes. This is clogging your converters, as well as...

Q: My car won't start and the check engine light and check oil lights are on

The clicking sound can occur when there is not enough battery power getting to the starter to crank the engine. If the cables were corroded, then the battery may be sulfated and need to be replaced. A simple battery check...

Q: Getting error codes P0599 and P0171. Ive cleaned the O2 sensors but have no idea where to go from here.

Hello. Code P0599 is the code for an issue with the thermostat heater control circuit, while P0171 is for a lean condition on bank 1. P0599 is set when the computer detects that there is an issue with the electronically...