P0171 Buick Code - Fuel Trim System Lean Bank 1
Quick Answer
The Engine Control Module (ECM) controls a Closed Loop air/fuel metering system to provide the best possible combination of drivability, fuel economy, and emission control. Common causes include Dirty or Restricted Air Filter, Dirty or Faulty Mass Air Flow (MAF) Sensor, Intake Air Leaks. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P0171 Buick indicates Fuel Trim System Lean Bank 1.
- Common causes
- Common causes include Dirty or Restricted Air Filter, Dirty or Faulty Mass Air Flow (MAF) Sensor, Intake Air Leaks.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code P0171 Buick Description
What are the Possible Causes of the DTC P0171 Buick?
- Dirty or Restricted Air Filter
- Dirty or Faulty Mass Air Flow (MAF) Sensor
- Intake Air Leaks
- Exhaust Gas Leaks
- Fuel Contamination
- Faulty or Clogged Fuel Injectors
- Faulty Front Heated Oxygen Sensor
- Ignition Misfiring
- Low Fuel Pressure
- Positive Crankcase Ventilation (PCV) Hose Leaks
- Engine Control Temperature (ECT) inaccurate readings
How to Fix the DTC P0171 Buick?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
Click Here to Learn What is Bank 1 and Bank 2
There is a Factory Service Bulletin for all 2000-2013 Buick models:
2000-2013 Buick Factory Service Bulletin OBDII Code P0171
User Submitted Video
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0171 Buick code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
Need more information about the P0171 Buick code?
Need more information on how to fix the P0171 Buick code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P0171 Buick code diagnosed by a professional: Find a repair shop in your area
Information for Specific Buick Models
- P0171 2002 Buick LeSabre — Fuel Trim System Lean Bank 1
Frequently Asked Questions about P0171 Buick Code
1. What are common symptoms of OBDII code P0171 in a Buick?
- Common symptoms include rough idling, loss of power, decreased fuel efficiency, and illuminated Check Engine Light.
2. What does the OBDII code P0171 on a Buick indicate?
- OBDII code P0171 indicates a "Fuel Trim System Lean Bank 1" condition, meaning the engine is running too lean due to an imbalance in the air-fuel mixture.
3. What are the possible causes of OBDII code P0171 on a Buick?
- Possible causes include a vacuum leak, faulty oxygen sensor, clogged fuel filter, malfunctioning mass airflow sensor, or issues with the fuel injectors.
4. How can I diagnose the OBDII code P0171 on my Buick?
- Diagnose the code by checking for vacuum leaks, inspecting the oxygen sensor, testing the mass airflow sensor, examining the fuel injectors, and ensuring the fuel pressure is within specifications.
5. Can a dirty air filter trigger OBDII code P0171 in a Buick?
- Yes, a dirty air filter can disrupt the air-fuel mixture and contribute to a lean condition, potentially triggering OBDII code P0171.
6. How should I repair OBDII code P0171 on my Buick?
- Repair steps may include fixing vacuum leaks, replacing the oxygen sensor, cleaning or replacing the mass airflow sensor, replacing the fuel filter, or addressing issues with the fuel injectors.
7. Is it safe to continue driving my Buick with OBDII code P0171?
- It is not recommended to continue driving with OBDII code P0171 as it can lead to engine damage and decreased performance. Prompt diagnosis and repair are advised.
8. Will resetting the Check Engine Light resolve OBDII code P0171 in a Buick?
- Resetting the Check Engine Light will only clear the code temporarily. The underlying issue causing OBDII code P0171 needs to be diagnosed and repaired to prevent it from reoccurring.
9. Can extreme weather conditions affect the occurrence of OBDII code P0171 in a Buick?
- Yes, extreme weather conditions like extreme heat or cold can affect air density and impact the air-fuel mixture, potentially triggering OBDII code P0171.
10. How can regular maintenance help prevent OBDII code P0171 in a Buick?
- Regular maintenance, including changing air filters, inspecting vacuum lines, and ensuring proper fuel system function, can help prevent issues leading to OBDII code P0171.
Discuss the causes and fixes for P0171 Buick OBDII Code
-
What model and year is your Buick. You should start by inspecting you Buick for intake leaks.
-
-
On the 2014 Encore (1.4L turbo), P0171 is very common and usually comes down to a few specific problem areas.
The big one on these is air leaks. That engine uses a lot of plastic hoses and fittings that get brittle and crack over time. The most common spots I see:
• PCV system built into the valve cover
• The small PCV hose from the intake to the valve cover
• Intake air duct between the MAF and turbo
• Vacuum lines around the intake manifoldAnother very common issue on the Encore is the valve cover/PCV failure. When the PCV diaphragm goes bad, it creates a vacuum leak and sets P0171. You may also hear a whistling noise or notice rough idle.
Other things to check:
• Dirty or weak MAF sensor
• Boost leaks (since it’s turbocharged, any leak after the MAF will cause a lean condition)
• Intake manifold gasket leaks
• Exhaust leak before the O2 sensorFuel pump issues are less common on these compared to air leaks.
If you want to narrow it down quickly:
• Check fuel trims at idle vs higher RPM — if it’s worse at idle, it’s almost always a vacuum leak
• Inspect the valve cover/PCV system closely
• Smoke test the intake if possibleOn that engine, I’d start with the PCV/valve cover and intake hoses before anything else. That’s where most P0171 problems come from on the Encore.
-
-
-
97 Buick lesabre throws p0171 &p0306 ... replaced upper & lower intake manifold and gaskets, plugs&wires ,coilpack, back O2sensor, oil pan gasket, Maf ,Map,Tbs sensors and fuel filter . Ruff idle at start takes a while longer to warm up ,smell an excessive amount of fuel.
-
i have a 2000 buick regal supercharged and it throws a p0171 bank 1 lean code i have changed mass air flow sensor , oxygen sensor, throttle position sensor plugs, today i found the problem it was the flex pipe that goes into the intake coming from the egr . hope thie saves some else some time and money . God bless!
-
"The flex pipe that goes into the intake coming from the egr"...can you elaborate? I'm getting p0171 on our 03 LeSabre.
-
well yo need to find the egr valve mine has to metal flex pipes comming in and out of it they can also leak up where they bolt on . i sprayed carb cleaner while it was running and found mine . but mine is supercharged maybe you dont have the same set up im not sure
-
Thanks for the info. This isn't a supercharged model so I don't know if the setup is the same.
-
I have an 04 LeSabre custom 3.8 seriesll, car is immaculate, 55 on highway, ses light starts flashing,running rough, replaced coil pack,plugs,etc. have spark to all plugs, no intake leaks,checked injectors, cps sensor,maf,pcv,oil is fine, camshaft position sensor,air filter is new.
-
Have you read the bulletin listed under "Tech notes"? you could have a clogged fuel injector. Try using high octane gas for a couple of weeks and if possible add some fuel additive to clean the injectors.
-
2002 Buick K 3800 eng .Sets po171,ltft reads 17%,everthing else looks good,suspect vac leak, but nothing shows up when spraying carb cleaner everywhere .o2sensor seems a little sluggish .I haven't replaced any parts yet,but intend to replace upper manifold and lower manifold gaskets.the code isn;t supposedto set until ltft is at 23%.any other ideas?????
-
According to a national database of repairs, the most common component that can trigger the P0171 code is the Mass Air Flow (MAF) sensor.
-
I had a P0171 on my 2015 Buick Encore. The first sign of an issue I saw was on cruise control struggling to get uphill to high speeds. It got worse to the point where it would be jumpy at stop signs. I found it strange that the check engine light would go off when it got cold outside, but when the weather got above 70 degrees out, the check engine light would come back on, and eventually it stayed on. The first guy that ran the codes said it was the turbocharger. After some research I was a little worried I was going to have to spend $500-$1000 and all weekend to fix it if I even could. I had AutoZone run the codes again a few weeks later and the MAF sensor came up along with the running lean code. I first cleaned the MAF sensor with cleaner from auto zone which was like $10 or $15, but the running lean code was still there. After more research I narrowed it down to the camshaft cover. It cost me $65 on Amazon. The GM website had it too, but Amazon got it to me a week faster.
The hardest part was the clips, but it is a pretty easy fix. Took me like an hour, and I've done pretty much no mechanic work ever. It is often mistakenly referred to as PCV valve, and is common in the 1.4 liter ecotec engine for a Volt, Cruze, Trax or Sonic.https://www.youtube.com/wat...
https://www.youtube.com/wat...https://www.amazon.com/gp/p... - You can search for car parts using your VIN number online
-
I have a 1999 buick Lesabre . Where is the Flex pipe. Where would it be ?
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
