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Q: P0171 & P0174

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Shortly after an oil change, I got the following codes - P0174 & P0171. I am assuming it is a fuel system pressure issue. Are there any simple checks or fixes I can perform before taking it to a mechanic - hoping to save some money.

My car has 98000 miles.
My car has an automatic transmission.

A: These two trouble codes are both related to...

These two trouble codes are both related to the oxygen sensors located after the catalytic converter detecting that your vehicle is running lean. There could be a fuel pressure problem, vacuum leak, a vacuum hose left unplugged, an intake air tube not fully seated/loose, or any number of other possible causes. You may be able to do a visual inspection to see if any hoses were left off, or maybe a sensor left unplugged. If this happened within a day or two of the oil change, I would take it back to them and explain the situation. If nothing else, I would expect them to at least offer to do a visual inspection to be sure it wasn’t something they missed. If you’re still in need of help, YourMechanic offers a repair and diagnosis service preformed by a certified mechanic that will commute to your location to look further into these trouble codes.

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