GMC Acadia P2276: B2S3 O2 Sensor Stuck Lean

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P2276 GMC Acadia

P2276 is a general diagnostic trouble code.  It means that your GMC Acadia’s third (from the exhaust manifold) “bank 2” downstream oxygen sensor (behind the catalytic converter) is continuously sending voltage that indicates a lean air/fuel mixture.  

Having this code does not necessarily mean that the vehicle is running lean (although it can, but usually doesn’t).  P2276 is typically caused by a bad oxygen sensor or an exhaust leak.

Bank 2 Sensor 3 Location

P2276 Diagnosis GMC Acadia

There are oxygen sensors on both sides of your GMC Acadia’s catalytic converter(s).  This lets your Acadia’s PCM read the exhaust before and after it has run through each converter to make sure that it is removing pollutants and that the air/fuel mixture is correct.

Here’s what P2276 means, and how to find Bank 2 Sensor 3.

P2276: O2 Sensor Signal → Biased/Stuck Lean (Bank 2 | Sensor 3)

  • Bank 2 is the side of the engine with the second cylinder.  On four-cylinder engines, you don’t have to worry about this, as there is only one cylinder head.  If you do have more than one cylinder head (as is the case here), you will need to look up where cylinder one is for your particular engine.  P2274 indicates the same problem for bank 1.
  • Sensor 3 is “downstream” of the catalytic converter.  To find it, you’ll need to start counting form the bank 2 exhaust manifold.  Sensor three is the third sensor back (it’ll more than likely be the last one).

GMC Acadia P2276 Symptoms

There are almost never any symptoms associated with P2276.  This code indicates that the signal coming from your Acadia’s oxygen sensor at B2S3 is leaner than it should be.  

The signal from the oxygen sensor upstream of the catalytic converter does not agree with the lean condition indicated by the downstream oxygen sensor.  If it did, you’d have P0171.

There are usually no drivability issues when P2276 appears by itself.

GMC Acadia P2276 Causes

Here are some of the more common causes of P2276.

Exhaust Leak (Likely)

An exhaust leak is one of the more common reasons why P2276 is thrown.  If an exhaust leak is big enough to cause P2276, it’s probably going to be big enough to make some noticeable noise.  

Oxygen Sensor (Highly Likely)

Acadia P2276 Causes
Your O2 sensor will be under the car after the catalytic converter.

If there isn’t an exhaust leak, the most likely cause of P2276 is a bad Oxygen sensor.  Take a look at the wiring going to it and see if it looks cracked or corroded.  This happens a lot. The O2 sensor wiring harness (due to its proximity to the exhaust system) has a rough life.

You can check the wiring harness with a multimeter set to OHMS.  Check the resistance compared to the factory specs.  Or if your Acadia has dual exhaust, check it vs the other downstream O2 sensor.

You can also check the voltage at the oxygen sensor if you have a good scan tool.  It should fluctuate as you press the gas.  If it’s stuck at 0, that would indicate that the sensor itself is bad.

You can swap the bank 1 sensor 3 sensor with the bank 2 sensor 3 O2 sensor and clear the codes.  If the code changes to P2274, you know the sensor is bad.  If the code stays P2276 you know that something else is causing the code.

Other Causes

  • Low fuel pressure
  • Loose O2 sensor
  • Bad fuel injector on bank 2
  • Bad purge valve
  • Bad PCM (particularly some Chrysler vehicles)

Conclusion

It’s normally the oxygen sensor that needs to be replaced when P2276 appears.  But, there can be other issues as well.  Good luck fixing your GMC Acadia!