P0171 on Chevy: Causes, GM Bulletins and Fixes

By CodeRight Auto Editorial TeamPublished 7 min read

Small turbocharged four-cylinder engine with a plastic camshaft cover and PCV hose

Quick Answer

P0171 on a Chevrolet means bank 1 is running lean, the same as on any car. What is specific to Chevy is the 1.4L turbo engine in the Cruze, Sonic, Trax and Volt: GM bulletin 19-NA-114 says P0171 on these engines may be caused by a torn PCV diaphragm in the camshaft cover, which lets unmeasured air in. On other Chevys, start with the usual lean checks.

On this page
  1. What does P0171 mean on a Chevy?
  2. What makes P0171 different on Chevrolet?
  3. Does the GM bulletin apply to my Chevy?
  4. Is it safe to drive a Chevy with P0171?
  5. What should you check on a Chevy with P0171?
  6. How do you fix P0171 on a Chevy, and what does it cost?
  7. Frequently Asked Questions
  8. Our Take
  9. Sources

Key Takeaways

  • P0171 on a Chevy is a "fix soon" code: you can usually drive, but stop if the check engine light flashes or the engine shakes.
  • GM bulletin 19-NA-114 covers the 1.4L turbo in the 2011 to 2016 Cruze, 2012 to 2019 Sonic, 2013 to 2019 Trax and 2012 to 2015 Volt, plus related Buick and Cadillac models.
  • The suspect is a torn PCV crankcase pressure control diaphragm built into the camshaft cover; the GM fix is a new camshaft cover.
  • GM says the PCV valve must be tested before the cover is replaced, and the oil dipstick and oil cap must seal first.
  • Other Chevrolet engines get the standard checks: intake leaks, MAF sensor, fuel pressure.

P0171 at a glance

Meaning
System Too Lean (Bank 1)
System
Fuel & Air
Severity
Fix Soon The car usually still drives, but a lean mixture can cause hesitation, misfires and overheated parts, so get it diagnosed soon and stop if the check engine light starts flashing.
Common causes
  • Vacuum or intake air leak after the MAF sensor
  • Dirty or failing mass airflow (MAF) sensor
  • Weak fuel pump or clogged fuel filter (low fuel pressure)
  • Restricted or leaking fuel injector
  • Faulty upstream oxygen sensor
Chevrolet specifics
GM bulletin 19-NA-114 says P0171 on the 1.4L turbo (LUJ, LUU, LUV) may be caused by a torn PCV crankcase pressure control diaphragm in the camshaft cover; after a PCV test confirms it, the fix is a new camshaft cover. Applies to: 2011-2016 Cruze, 2012-2019 Sonic, 2013-2019 Trax, 2012-2015 Volt with the 1.4L (also 2013-2019 Buick Encore, 2014-2017 Cadillac ELR). Bulletin 19-NA-114.
Applies to
Generic OBD-II code: same meaning on all 1996 and newer cars and light trucks sold in the U.S.

Read the full P0171 guide · Look up another code · Data checked November 2026

What does P0171 mean on a Chevy?

P0171 means the engine computer has added as much fuel as it can on bank 1, and the exhaust still reads lean. Bank 1 is the side with cylinder 1; four-cylinder engines like the 1.4L turbo have only one bank. ALLDATA DIY describes a lean code as too much air, not enough fuel, or both [4].

The definition does not change by make. What changes is which faults show up again and again. Our main P0171 guide covers the general causes and fuel trims. This page covers what GM has published about Chevrolet engines.

What makes P0171 different on Chevrolet?

GM has published bulletins that tie P0171 on its 1.4L turbo engine to a leak in the PCV system built into the camshaft cover. The current one is bulletin 19-NA-114 (May 2019), "Information on Malfunction Indicator Lamp (MIL) Illuminated, DTC P0171 Set." It applies to these models with the 1.4L engine (RPO LUJ, LUU or LUV) [1]:

  • Chevrolet Cruze, 2011 to 2016
  • Chevrolet Sonic, 2012 to 2019
  • Chevrolet Trax, 2013 to 2019
  • Chevrolet Volt, 2012 to 2015
  • Buick Encore, 2013 to 2019, and Cadillac ELR, 2014 to 2017

GM says the condition may be caused by a torn positive crankcase ventilation (PCV) crankcase pressure control diaphragm. A torn diaphragm lets un-metered air into the crankcase, and from there into the engine, so the computer sees a lean mixture. The bulletin is public on NHTSA's document server, static.nhtsa.gov.

This is not new. An earlier GM bulletin, PI0850 from November 2012, described a whistle from the engine compartment, a rough idle and/or P0171 on the 2011 to 2012 Cruze 1.4L, caused by a vacuum leak in the PCV on the camshaft cover. That bulletin's fix was a camshaft cover of a newer design with a flatter PCV cap [2].

How a torn PCV diaphragm causes P0171 on the 1.4L turbo Simplified side view. The PCV valve with its diaphragm sits in the camshaft cover on top of the engine. A torn diaphragm lets outside air in through the PCV vent, into the crankcase and then the intake, bypassing the MAF sensor. Dipstick and oil cap must also seal. Simplified, not to scale Camshaft cover Engine and crankcase PCV valve diaphragm Unmetered air Oil cap Dipstick Air leaks in here, after the MAF sensor measured it
On the 1.4L turbo, the PCV valve and its diaphragm are part of the camshaft cover. A tear lets air into the engine that the MAF sensor never measured.

Does the GM bulletin apply to my Chevy?

It applies if your vehicle is one of the models above and has the 1.4L turbo engine. The Cruze was also sold with other engines, such as the 1.8L, so check which engine yours has. The engine size is usually printed on the engine cover, listed in the owner's manual, and encoded in the VIN. Our VIN decoder can confirm the model year and engine, and a Chevrolet dealer can check your VIN for open bulletins and any special coverage.

GM's own wording is careful: its bulletins are written for professional technicians, and an owner should not assume a bulletin applies to their vehicle or that their vehicle has the condition. If you drive a different Chevrolet, such as a Silverado or an Equinox, we found no GM bulletin we could verify that ties P0171 to a single part, so diagnose it like any other lean code.

Is it safe to drive a Chevy with P0171?

Usually yes for a short time, but treat it as "fix soon." Carista lists rough idle, possible stalling, hesitation, reduced power and idle misfires as typical P0171 symptoms [5]. On the 1.4L turbo, GM bulletins also mention a whistle from the engine compartment.

Pull over when it is safe and stop driving if the check engine light starts flashing or the engine shakes. The California Air Resources Board explains that a blinking light means a malfunction that could be damaging the catalytic converter [6]. See our guide to a flashing check engine light, and P0300 if misfire codes appear.

What should you check on a Chevy with P0171?

Start with a scanner and the free checks. Our guide on how to use an OBD2 scanner explains freeze frame and live data.

  1. Read every code and the freeze frame. On the 1.4L, note any P0300 or P0299 too.
  2. Make sure the oil dipstick is fully seated and the oil filler cap is tight. GM lists this as the first step before testing the PCV valve, because both seal the crankcase.
  3. Listen at idle for a whistle near the top of the engine. Keep hands, hair and loose clothing away from belts and the fan.
  4. Have the PCV valve tested. In 19-NA-114, a technician checks whether the PCV valve is noisy and whether vacuum is present at its vent, using a tissue or smoke. If the valve is noisy and pulling vacuum at the vent, GM's fix is a new camshaft cover. If not, the PCV system is not the cause and normal diagnosis continues.
  5. Standard lean checks. Intake boot, vacuum hoses, MAF sensor, then fuel pressure by a technician.
  6. Ask about oil use. GM preliminary information PIP5197J notes that on these engines a weak or broken piston ring land can cause P0300 and may also damage the PCV diaphragm, causing P0171, so it pays to know whether the engine is burning oil [3].
GM 1.4L P0171 check order from bulletin 19-NA-114 Step 1: seat the dipstick and tighten the oil cap. Step 2: listen for noise from the PCV valve with the engine running. Step 3: check for vacuum at the PCV vent. If noisy with vacuum, replace the camshaft cover. If not, the PCV system is not the cause; continue normal lean diagnosis. 1. Dipstick seated, oil cap tight 2. Listen: noise at PCV valve? 3. Vacuum at the PCV vent? Noise + vacuum No Replace camshaft cover (GM fix) PCV not the cause: normal lean checks
GM says the PCV valve must be confirmed bad before the camshaft cover is replaced.
Generic P0171 causesChevrolet 1.4L turbo (GM 19-NA-114)
Which vehiclesAny make or model2011 to 2016 Cruze, 2012 to 2019 Sonic, 2013 to 2019 Trax, 2012 to 2015 Volt, plus Encore and ELR
Typical complaintRough idle, hesitation, weak powerCheck engine light, sometimes a whistle and rough idle
Main causeAir leak, MAF sensor, low fuel pressureTorn PCV diaphragm in the camshaft cover
First checkScanner data, hoses, intake bootDipstick and oil cap seal, then PCV valve test
FixRepair the leak or failed partNew camshaft cover after the PCV test confirms it

How do you fix P0171 on a Chevy, and what does it cost?

On a 1.4L turbo where the PCV test confirms a torn diaphragm, GM's fix is a new camshaft cover, because the PCV valve is part of it. On other Chevrolets, the fix is whatever the diagnosis finds, from a cracked hose to a MAF sensor or fuel pump.

We do not quote a price, because we found no reliable public cost data for this job as of November 2026. Cost depends on the part, labor time on your engine, diagnostic time, and whether any warranty or special coverage applies. Before paying for the repair, ask a Chevrolet dealer to check your VIN for any open bulletin, recall or coverage that applies; we could not verify extended coverage terms for this part from a primary source.

After the repair, clear the code and drive normally. Clearing a code does not fix anything, and it resets the readiness monitors. California requires all readiness monitors to be set to pass Smog Check, and they complete through normal driving or a drive cycle [7].

Frequently Asked Questions

Why does my Cruze whistle and show P0171?

On the 1.4L turbo, GM bulletin PI0850 linked a whistle, rough idle and P0171 to a vacuum leak in the PCV on the camshaft cover [2]. The newer bulletin, 19-NA-114, describes the same part: a torn PCV diaphragm. Have the PCV valve tested before replacing parts.

Can I just replace the PCV valve on a 1.4L Cruze?

On this engine, the PCV valve and diaphragm are part of the camshaft cover, so GM's repair is replacing the camshaft cover. GM also says the PCV valve's performance must be confirmed before the cover is replaced, so the test comes first.

My 1.4L also burns oil. Is that related to P0171?

It can be. GM preliminary information PIP5197J groups oil consumption, blue exhaust smoke, a whistle and codes P0171, P0300 and P0299 on these engines. It defines excessive oil consumption as about 1 quart or more within 2,000 miles when there are no leaks. The document says a weak or broken piston ring land can cause P0300 and may damage the PCV diaphragm, and it also tells technicians to check for a missing non-return valve in the intake manifold [3]. If your engine uses oil and keeps tearing PCV diaphragms, a new camshaft cover alone may not end the problem, so ask the shop to look at the cause too.

Does P0171 on a Silverado mean the same thing?

The code means the same thing, but the GM bulletin above does not cover the Silverado's V8 engines. On a V8, also check whether P0174 is set; both banks lean points to a shared cause like an intake leak, the MAF sensor or fuel pressure.

Our Take

We think the 1.4L turbo story is a good example of why a quick bulletin check beats guessing. GM has documented the same failure point, the PCV diaphragm in the camshaft cover, in bulletins going back to 2012, and it spells out a simple test before any parts are replaced. If you own one of these models with P0171, we would first make sure the dipstick and oil cap seal, then ask a dealer or shop to run GM's PCV test and check your VIN for coverage. For other Chevrolet engines, we found nothing make-specific to verify, so we would follow the standard order: scanner data, intake leaks, MAF sensor, then fuel pressure.

Sources

  1. Bulletin 19-NA-114: Information on Malfunction Indicator Lamp (MIL) Illuminated, DTC P0171 Set. General Motors via NHTSA, 2019.
  2. PI0850: Whistle Noise Heard from Engine Compartment, Rough Idle and/or DTC P0171 Set. General Motors via NHTSA, 2012.
  3. PIP5197J: Possible Oil Consumption, Leaks, Blue Smoke Exhaust, Whistle Noise, DTC P0171 and/or P0300 and/or P0299. General Motors via NHTSA, 2018.
  4. What Common OBD-II Codes Really Mean. ALLDATA DIY, 2026.
  5. P0171 Code: Fuel Trim System Too Lean (Bank 1). Carista, 2026.
  6. On-Board Diagnostic II (OBD II) Systems Fact Sheet. California Air Resources Board, 2019.
  7. New OBD readiness monitor regulations explained. California Bureau of Automotive Repair, 2025.

This is general information to help you understand your vehicle, not a substitute for a hands-on diagnosis. If a warning light is flashing or the car runs badly, stop driving and have it checked by a qualified technician. Spotted an error? Tell us.