Skip the auto shop - Our mechanics make house calls

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.

A: The codes you have for your GMC Yukon, p017...

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?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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: P0300 and P0305. Pending: P0304, P0306, P0171, P0174, P2196, P2198

Hi there. The issue that maybe happening is the are fuel injectors that are not firing and there is a vacuum leak on the engine. Possible multiple sensors are not working causing the P2196 and P2198 codes to appear. For...

Q: ABS light on

There is a technical service bulletin (TSB) GM has put out concerning a bad ground to the electronic brake controller module or EBCM. This causes a loss of communication and sets the ABS light. There are fault codes associated with...

Q: Oil change place could not do oil change because plug is stripped. What do u recommend?

Hello, If you cannot remove the oil plug then have the oil removed using the dip stick tube with a suction machine. I use this on vehicles on the road and can suck all the oil out through the dipstick...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.