Skip the auto shop - Our mechanics make house calls

Q: Codes showing: P0171, P0420, P0174

asked by on

"We have a minivan and it's showing several codes: P0171 - bank 1-combustion too lean, P0420 - catalyst eff. too low, P0174 - combustion to low What do these things mean. I'm not auto savvy and need to understand before seeing a mechanic."

Hello. These diagnostic trouble codes are an indication that there could be a problem with the oxygen sensor or that there is a vacuum leak. It is possible that the vacuum leak is located in the intake manifold. These codes could also simply be the result of a loose hose. I would suggest that you have a certified technician, like one from YourMechanic, come out and complete an inspection to determine why your check engine light is on.

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: Heater not working and car overheating.

The first thing to check is if the coolant is low. This car is known to have a problem with the radiator leaking coolant on the sides and may have leaked most of the coolant out. This is why your...

Q: P0420 code and dash lighs on

The vehicle stability control (VSC) light and code P0420 are for two different problems. The VSC system would need to be tested for codes for that system. The code P0420 is for the O2 sensor or problem with...

Q: Still getting error codes

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...

Related articles

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 Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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...