Q: Getting codes P0171 and P0174 with Service Engine Light on.

asked by on

Last week I noticed my Service Engine Light came on when it was really cold outside. I borrowed my buddies OB2 scanner and it came back with codes P0171 and P0174. So I researched on google and started eliminating items it could be. I cleaned the air filter, cleaned the MAF sensor with MAF cleaner, replaced the PCV elbow hose by the PCV valve as it had a small hole in it, and put a new fuel filter on. Reset the light and it came back on this morning a day later. Engine idles great, starts right up when you start it, and no acceleration issues that I'm noticing. Autozone said it's my fuel pump but that doesn't make any sense to me as a bad failing fuel pump your car/truck would be hard to start or not start at all and you would have drivability issues which im not having. Anyways, any help would greatly be appreciated. Thanks! :)

My car has 219000 miles.
My car has an automatic transmission.

P0171 and P0174 say the system is too lean on both banks. That means that whatever is causing the problem is common to both sides. The first thing to check for is air leaks, but it sounds like you have already been there. Doesn’t hurt to look again though, I’d say 8 out of 10 of the P0170’s that I fix are air leaks. As for the fuel pump, you are half right. But there might be a problem with fuel pressure. Your truck probably has a pump in the tank with an integral pressure regulator. At 200 thousand miles that is possibility. The way to check this is to do a fuel pressure test. If you decide to get some help with this, contact YourMechanic. They will send a technician to your home or office to check out your ford and let you know what is the solution.

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. Getting codes P0171 and P0174 with Service Engine Light on.

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: Q: Rough Idle

Since the check engine light came on you will want to have a computer scan for stored codes. This may indicate the cylinder that is misfiring or having issues and then further diagnosis on that cylinder can be done to...

Q: when in reverse the car gets stuck or its hard backing up.

Hi there. For your car this is the first sign of transmission failure. When the car starts having issues going in reverse, either it has burnt out internal clutches, or the gear housing is cracked and binding. Either way, you...

Q: Q: Coolant

You should keep the coolant full at all times making sure to be careful topping off coolant when engine is hot. If you notice engine running hot you should stop and let the engine cool before adding more coolant or...

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 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.