One of the most common trouble codes with the Cadillac STS is the P0174 code. This code number references a number that is given to you when you plug your truck into a OBDII scanner. The code is often accompanied by the P0171 code, which has the same set of symptoms, but is for bank one.
P0174: Fuel Trim System Lean Bank 2
STS P0174 Code Defined
P0174 is an OBDII trouble code. The code technically stands for:
Fuel Trim System Lean Bank 2
The code is thrown when the oxygen sensors detect that there’s not enough oxygen in the exhaust system. This is commonly referred to as a “lean” condition.
The vehicle’s ECM will add more fuel to the mixture in order to bring the air fuel mixture where it needs to be for optimal combustion. It also throws the code P0174 to let you know that it has done this.
STS P0174 Code Symptoms
The P0174 code on a Cadillac STS will often be thrown if the fuel injection system is not operating properly. Typically the code will be triggered by a lean condition in the engine.
There aren’t usually any drivability issues associated with P0174. For most people the first sign that anything is wrong at all is the service engine soon light coming on.
Here are the typical symptoms that something is wrong when you have code P0174.
- Mileage- may or may not suffer depending on how much the air fuel mixture has changed.
- Misfire– If the air fuel mixture has gotten too far from factory specs, this can cause the STS to misfire.
- Idle Issues– With the air/fuel mixture altered, the vehicle can idle erratically as the computer compensates to keep the engine running.
Cadillac STS P0174 Causes
Here’s a helpful video:
There are many things that can cause the P0174 trouble code on the Cadillac STS. The most common problem is far and away the first one listed below.
- Vacuum Leaks– With the Cadillac STS, the most common cause for the P0174 code to show is a vacuum leak. Take a look around and see if you can find the vacuum leak. Here’s a great YouTube video on how to find a vacuum leak.
- Mass Air Flow Sensor– The mass air flow sensor calculates the volume of air entering the engine. If it has gone bad, the air fuel mixture will be off and the P0174 code will show.
- Bad Fuel Injectors– If you have one or more fuel injectors that have gone bad that can certainly cause the air/fuel mixture to go bad.
- Fuel Pump/Fuel Filter– Today’s modern fuel injected motors need a lot of fuel pressure to atomize the gas properly. If the fuel pressure is not as high as it needs to be this atomization doesn’t happen properly and the optimal air/fuel mixture isn’t achieved.
Good luck figuring out what is wrong with your STS. If there are any inaccuracies, or anything that you feel could improve the article, please feel free to comment or message. Thank you.