Q: Engine light on with P0171 code

asked by on March 07, 2017

Good morning. I'm having issues with my truck. (2002 GMC Sierra 1500 SLT 4WD)I bought it from a used car lot and the truck runs well no noticeable issues. Three days after I buy it boom engine light turns on. I'm really upset because the lot I bought it from more then likely reset the codes before I bought it because I had 3 codes pop up 3 days after I got it. What a coincidence, right? Anyway ran a obd II and had codes P0440, P1626, P0171. Went to a shop ran a diagnostic and they told me The PCV valve needed to be replaced and also the evap canister as well because it had water in it. 390$ later I'm driving with no engine light. We'll truck drives fine and no issues I don't smell anything and 1 day after I get it from the shop the Engine light turns on again. It's P0171 (system too lean bank 1). Any suggestions on where to start? MAF sensor is clean and I was thinking about a changing the fuel filter today. How can I pinpoint the exact issue?

My car has 149029 miles.
My car has an automatic transmission.

Check Engine Light is on Inspection $79.99 - $89.99 Get a Quote

The cause behind diagnostic trouble code P0171 is easiest to find by looking at the secondary firing patterns on the Bank one cylinders. That will confirm if the too lean condition, that has caused the code to set, affects all cylinders in the bank. If not all cylinders are affected, test for defective individual fuel injectors. However, if all cylinders are affected, you would test, in turn: the fuel pressure regulator, fuel pump pressure, check for a clogged fuel filter, vacuum leak, faulty oxygen sensor(s) and faulty mass air flow sensor. Rarely, the cause will be a faulty powertrain control module. If you want these steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a check engine light diagnostic - code P0171 and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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

low gas mileage

Decreases in fuel economy are caused by things like fuel control issues (fuel injector leaks, bad O2 or other sensors), transmission problems (won't shift into high gear, slipping, torque convertor clutch fails to lock-up), misfires (ignition related), low tire pressure,...

Do I need a whole new ignition or just the ignition switch?

You will need to have the damage to the ignition lock cylinder housing checked to see if just the lock cylinder can be replaced if no damage to housing was done. You will need to have the door and trunk...

my temperature gauge rises slowly when its in drive and idle. once i start driving, it quickly drops. what could be the issue?

Hi there. From the description you have provided, this could be an inoperative radiator cooling fan issue. Turning on the a/c, this should turn the radiator cooling fan(s) on, which would help identify whether the cooling fan(s) are capable of...

Turn signals not flashing.

This is a common issue with many Ford vehicles. The faulty part would be your multifunction switch or turn signal switch. There is a mechanism that causes the switch to lock in place during a turn inside the switch that...

locate fuse for windshield washer on 2002 toyota camry

The windshield wiper fuse is located in the fuse junction box under the left side of the dash. The fuse is a 25 amp fuse. It will be labeled wiper. Check the fuse to see if it is burned out....

Check engine light is on.. Its not running any differently and it starts normally..

You need to have the engine computer scanned to see what trouble code is stored. Not all codes will cause the engine to run bad or cause a noticeable problem. For instance, a trouble code could be triggered by a...

All lights are on dashboard. Brake lights will not go off.

I suggest beginning by fixing what is already known first. The brake pedal switch needs to be replaced. That switch does much more than just turn on the brake lights, and is possibly the root cause of all of this....

Faulty speed sensor causing car to stall.

If you are referring to P0320 - Ignition/Distributor Engine Speed Input Circuit code, then the most common cause of the problem is the crankshaft position sensor. This sensor controls ignition timing of the engine and when it fails the computer...

My car won't go over 20 mph. It will start to shake vigorously once it hits 20 mph

Hello. The codes that you have listed are for engine misfires. P0300 is for random misfires, while P0304, P0305, and P0306 are for specific cylinder misfires. Misfires can be caused by many things. If you have already replaced the MAF,...

Related articles

How to Troubleshoot a Car That is Hard to Start
"Car not starting" is a common complaint among car owners and is caused by faulty car batteries, spark plugs, car starter, or fuel pump.
What Gases Does the OBD Detect in the Exhaust?
Your Your engine runs on combustion – fire – which creates exhaust gases. A wide range of gases are produced during normal operation, and they must be controlled because many of them become pollutants when released into the atmosphere. It’s...
10 Best Automotive Scanners
Automotive scanners are a great tool to get quick diagnostics on a car. The Donop Professional U480 can help you troubleshoot issues on the road.