P2274 in the Ford Mondeo is a general diagnostic trouble code. It means that the “bank 1” oxygen sensor (third oxygen sensor from the exhaust manifold, behind a catalytic converter) is continuously sending voltage that indicates a lean air/fuel mixture.
This does not necessarily mean that the vehicle is running lean (although it can, but usually doesn’t). P2274 is typically caused by a bad oxygen sensor, or an exhaust leak.
With the case of P2274, if the code is not accompanied by P2270, it’s a pretty good bet that a bad oxygen sensor is the problem. If the vehicle was running super lean, then P2270 (this is the code for the second oxygen sensor in line) should confirm that fact.
Bank 1 Sensor 3 Location
There are oxygen sensors on both sides of your Mondeo’s catalytic converter(s). This lets it read the exhaust before and after it runs through each converter to make sure that it is removing pollutants.
Here’s what P2274 means, and how to find Bank 1 Sensor 3.
P2274: O2 Sensor Signal → Biased/Stuck Lean (Bank 1 | Sensor 3)
- Bank 1 is the side of your Mondeo’s engine with the first cylinder. If it has a four cylinder engine, you don’t have to worry about this, as there is only one cylinder head. If you do have more than one cylinder head, you will need to look up where cylinder one is for your particular engine.
- Sensor 3 is “downstream” of the catalytic converter (you probably have more than one in line). It is the third oxygen sensor on the bank one side of the vehicle when you start counting from the engine.
B1S3= Bank 1 Sensor 3
P2274 Symptoms: Ford Mondeo
There are almost never any symptoms associated with P2274. It is indicating that the signal coming from the oxygen sensor at B1S3 is leaner than it should be, which is usually not correct.
The signal from the oxygen sensor upstream of the catalytic converter does not agree with the lean condition indicated by the downstream oxygen sensor s). If the three sensors agreed you’d have P0171.
There are usually no drivability issues when P2274 appears by itself.
P2274 Causes: Ford Mondeo
Here are some of the more common causes of P2274.
Exhaust Leak (Likely)
An exhaust leak is one of the more common reasons why P2274 is thrown. If an exhaust leak is big enough to cause P2274, it’s probably going to be big enough to make some noticeable noise.
Oxygen Sensor (Highly Likely)
If there isn’t an exhaust leak, the most likely cause of P2274 is a bad O2 sensor. Take a look at the wiring going to it and see if it looks cracked or corroded. The O2 sensor wiring harnesses (due to their proximity to the exhaust system) have some of the roughest lives of any automotive wiring.
You can check your Mondeo’s wiring harness with a multimeter set to OHMS. Check the resistance compared to the factory specs. Or if you have 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.
Other Causes
- Low fuel pressure
- Loose O2 sensor
- Bad fuel injector on bank 1
- Bad purge valve
- Bad PCM
Bottom Line: P2274 is Usually Caused by a Bad O2 Sensor
It’s normally the oxygen sensor that needs replaced when P2274 appears. But, there can be other issues as well. Good luck fixing your Mondeo!