Q: Still getting error codes

asked by on

I just changed the mass airflow sensor and I am still getting codes P0171 and P0174. I'm thinking it could be the O2 sensors.

The codes you have for your GMC Yukon, p0171 and p0174, are informing you that the engine is running lean. This means that there is unmetered air entering the engine after the mass airflow sensor and is disturbing the air/fuel ratio needed for your Yukon to run properly. Typically when both of these codes are present, it is a strong indication that the intake manifold gaskets have a vacuum leak. Attaching a vacuum gauge to the engine while it is running will quickly tell you how severe the vacuum leak is. In order to pinpoint the source of the vacuum leak, a special smoke machine needs to be hooked up to the engine. Typically, this is done right at the throttle body. Smoke will fill the intake manifold and vacuum hoses and once it finds a leak, smoke will seep out of it and will be visible to see.

I would recommend enlisting the assistance of a certified mechanic to come by and inspect your GMC Yukon. They will have the speciality tools and experience needed to determine exactly why your Yukon is running lean. They will also be able to perform the repairs necessary to eliminate the vacuum leaks and get your GMC running like a champ.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Still getting error codes

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Engine codes detected were P0016 P0017 and P0174.

The codes P0016 and P0017 are related to the crankshaft location and the camshaft location. Check the camshaft position sensor and see if its plugged in. If the wiring harness is in good shape and the wires are plugged in,...

Q: Need to replace O2 sensor

When a Check Engine Light is illuminated it can be scanned by a tool. The code that gets read by the computer signifies what needs to be changed/replaced. An O2 sensor code quite possibly may be the case, but a...

Q: Q: Car shakes at highway speeds

Hi! At your mileage the pads and rotors have of course been replaced or serviced before. It is likely due for another brake appointment. If the brakes are presenting issues it is not something that you should wait on. Waiting...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...