Q: Check engine light on & OBD #P0171

asked by on September 20, 2016

For three months, the Check Engine Light has been coming on and off. The Onboard Diagnostic #P0171 showed when I went in to have a checkup. The following have been replaced: gas cap, mass air-flow sensor, and spark plugs. The told me that it was the mass air-flow sensor because the system is running too lean. The check engine light still comes on every 2-3 weeks. I feel like I’m having the wrong things fixed. Please give me your professional advice on this problem.

Fuel Injector Replacement $379.42 - $3631.88 Get a Quote
Check Engine Light is on Inspection $79.99 - $89.99 Get a Quote

P0171 for your car is "system too lean." The most common cause is a vacuum leak and it can come from a leaky hose or a leaky gasket. However, I did a quick search and found someone on the forums with your exact car and exact problem and his issue was a leaky fuel injector seal. You may want to try that first since those are cheap. Alternatively, a qualified professional from YourMechanic can come to your car’s location to inspect the Check Engine Light firsthand to have this corrected appropriately.

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

What others are asking

Upon starting, the vehicle has a dry start for about 5 seconds unless it sits overnight.

Hi there. Check the oil pressure sensor and see if its working or sticking. When the oil pressure sensor is sticking or not working correctly, the computer will cut the ignition and fuel off until oil pressure is met and...

Noise and shaking after the car is put into gear, coolant light on

You'll need to check the coolant level before driving further. I would also have the mechanic check for a blown head gasket (which would cause the uneven running), and to make sure nothing under the vehicle is dragging. It is...

Transmission jerks, goes into limp mode, loss of power - 2006 Mercedes-Benz B200

Hello. It sounds like there is a problem with either the transmission control module and/or its wiring. There could also be a problem with the transmission valve body or clutches and if either of these are worn out this may...

Heater works intermittently, when not working car overheats and thermostat is new

Hi there. In most cases, when you have issues with the heater working and the vehicle overheating, it's caused by an obstruction of coolant inside the heater core. The cooling system circulates hot coolant / water into the heater core...

where is the location of crank position sensor in 2001 s600

Hello, thank you for writing in. The crankshaft position sensor is located on the back of the engine towards the top of the transmission bell housing. It will be towards the driver's side, and be tucked in close to the...

I purchased a flood damaged car and replaced the engine and on the computer it's saying system running lean. What does that mean?

Hi there. When the computer says that the bank 1 or bank 2 is lean, it is referring that the cylinders do not have enough fuel to burn. Check the injectors and see if they are plugged up. Look for...

Camshaft position sensor error code P0343

Hello. The P0343 code indicates there is no signal from the passenger side cam position sensor (Bank 1 actually). Given you have changed the sensor, this would suggest a wiring or connector issue. Your mileage would also make me anxious...

Car shakes when going over 60 MPH

This sounds like you have a problem with the front axles or speed sensors, along with front bearings failing. I recommend that you have a mechanic, such as ones from YourMechanic, come by and check your car for you, beginning...

Engine stutters then check light comes on at startup

Exhaust leaks can cause the check engine light to set. If you have an exhaust leak, it should be repaired because carbon monoxide is deadly. You can have the source of the leak identified, and repaired, by requesting an exhaust...

Related articles

Can a Bad Sensor Prevent a Car From Starting?
If your car isn't starting or has a hard time starting, a faulty sensor may be to blame. Car sensors monitor data to keep your car running smoothly.
The 10 Transmission Problems to Never Ignore
There’s nothing quite like transmission problems to stress out the average car owner. They are, at best, inconvenient and, at worst, very expensive. Proper...
What Does the Adaptive Cruise Control Warning Light Mean?
The adaptive cruise control (ACC) indicator light helps keep your car at a safe speed while driving by sensing the distance of the car ahead of you.