P0442 on 2013-2020 Buick Encore: EVAP Small Leak Causes and Fixes

What's Unique About the 2013-2020 Buick ENCORE

The 1.4L turbocharged engine used in the first-generation Buick Encore is also found in the Chevy Cruze, Sonic, and Trax. These vehicles share a common EVAP system design, and as a result, they also share common failure points. The most frequently replaced part for this code across this platform is the vapor canister purge valve (solenoid) located on top of the engine, which is known to fail by sticking open or closed. This part is so prone to failure that it is often the first component replaced after checking the gas cap, especially if code P0496 is also present.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• A faint smell of fuel, particularly around the outside of the vehicle
• Slightly reduced fuel economy
• Difficulty starting the engine or a rough idle immediately after refueling
• Audible clicking from a malfunctioning purge valve

Most Likely Causes

1. Loose or Worn Gas Cap 🔴 High Probability The gas cap is a frequently used component and its seal can degrade over time from exposure to fuel vapors and weather. It's the simplest and most common cause for any EVAP leak code.
   How to confirm: Ensure the gas cap is tightened until it clicks several times. Inspect the rubber O-ring on the cap for any cracks, stiffness, or damage. Also, check the fuel filler neck for rust or debris that could prevent a good seal.
   Typical fix: Tighten the cap. If the seal is damaged or the cap is old, replace it with a new one. It's recommended to use an OEM or high-quality aftermarket cap to ensure a proper seal. Aftermarket caps can sometimes fail to seal properly.
   Est. part cost: $15-$30
2. Faulty EVAP Canister Purge Valve/Solenoid 🔴 High Probability This specific part is a very common failure item on the 1.4L GM engine platform. It can get stuck open or closed, causing a leak or flow issue in the EVAP system. Its failure is so common it is often diagnosed along with code P0496.
   How to confirm: The purge valve is located on top of the engine. A simple test is to disconnect the electrical connector and the EVAP line coming from the gas tank side. With the engine running, if you can feel vacuum from the intake manifold side of the valve with your finger, it is stuck open and needs to be replaced. Another test is to remove the valve and try to blow through it; if air passes, it's stuck open and faulty.
   Typical fix: Replacement of the purge valve is straightforward and a popular DIY repair. It involves disconnecting two hoses and an electrical connector, then sliding the valve off its bracket. 🎬 Watch: Step-by-step guide to replacing the Encore purge valve.
   Est. part cost: $25-$60
3. Faulty EVAP Canister Vent Valve/Solenoid 🟡 Medium Probability Located near the charcoal canister by the fuel tank, this valve can get stuck or fail due to exposure to road debris and moisture. GM has issued service bulletins for similar vehicles regarding vent solenoid issues.
   How to confirm: Diagnosis is more complex and typically requires a bi-directional scan tool to command the valve closed while a smoke machine fills the EVAP system. If smoke escapes from the vent valve when it's commanded shut, it has failed. A DIY method involves removing the valve and applying 12V power to see if the solenoid actuates, or checking its resistance with a multimeter.
   Typical fix: Replace the vent valve solenoid, which is typically mounted on or near the EVAP canister under the rear of the vehicle, near the spare tire. 🎬 See how to replace the vent valve on this platform.
   Est. part cost: $30-$70
4. Cracked or Disconnected EVAP Hoses ⚪ Low Probability The plastic and rubber lines that make up the EVAP system can become brittle and crack over time, especially at connection points or bends.
   How to confirm: A visual inspection may reveal obvious cracks or disconnected lines, particularly at rubber elbows. However, small leaks often require a smoke test, where a mechanic fills the EVAP system with visible vapor to pinpoint the source of the leak.
   Typical fix: Replace the damaged section of hose or secure the loose connection. Use of hose clamps on connections can prevent future leaks.
   Est. part cost: $10-$50

Rare But Worth Checking

• Leaking EVAP Canister: The charcoal canister itself can develop a crack, especially if the vehicle has sustained an underbody impact. A GM Preliminary Information bulletin (PIP5862) for a slightly newer model suggests replacing the canister if no other leaks are found. A Reddit user with a P0442 on a Chevy Cruze had a smoke test confirm a leak from above the canister, pointing to a faulty canister or vent valve.
• Leaking Fuel Tank or Filler Neck: Rust or damage to the fuel filler neck can prevent the gas cap from sealing properly. While less common, the fuel tank itself or the fuel pump sending unit gasket can also develop a small leak, sometimes identifiable by a fuel smell.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0442 is present. Check if P0496 is also present, which strongly suggests a faulty purge valve.
2. Inspect the gas cap. Remove it, check the seal for cracks, and ensure it's the correct type for the vehicle. Clean the filler neck sealing surface. Tighten the cap until it clicks multiple times.
3. Clear the code and drive the vehicle for a few days to see if the light returns. The EVAP system self-test may require several drive cycles to complete.
4. If the light returns, locate the EVAP purge valve on top of the engine. Visually inspect its hoses for cracks or loose connections.
5. Test the purge valve. With the engine running, disconnect the EVAP line from the tank side of the valve. If you feel suction from the valve, it's stuck open and must be replaced. Alternatively, remove the valve and try blowing through it; if air passes, it is defective.
6. If the purge valve and gas cap are good, the next step is a professional smoke test. This involves injecting smoke into the EVAP system to visually identify hard-to-find leaks in hoses, the charcoal canister, or the vent valve.
🎬 Watch: How to find a small leak using a smoke test.
7. Based on the smoke test results, replace the leaking component, which could be the vent solenoid, a hose, or the canister itself. The vent solenoid is the next most likely part to fail after the purge valve.

Parts You'll Likely Need

• Vapor Canister Purge Valve / Solenoid (OEM #55573017) — This is the most common failure point on the 1.4L engine that causes a P0442 code, often accompanied by P0496. It is a well-documented issue across the GM platform.
  Trusted brands: ACDelco (GM Genuine), Bosch, Dorman
  OEM price range: $40-$60
  Aftermarket price range: $25-$45
• Fuel Cap (OEM #GT331 (ACDelco)) — A worn or loose gas cap is the simplest and a very common cause for a small EVAP leak.
  Trusted brands: ACDelco, Duralast, Stant
  OEM price range: $20-$30
  Aftermarket price range: $15-$25
• EVAP Canister Vent Valve / Solenoid (OEM #25950499 (ACDelco - check fitment)) — This valve, located near the fuel tank, can fail and get stuck, causing a leak. It's the next most likely component to check after the purge valve and gas cap.
  Trusted brands: ACDelco, Dorman
  OEM price range: $50-$70
  Aftermarket price range: $30-$50

Related Codes That Often Appear With This One

• P0455 — P0455 indicates a large EVAP leak. If a component fails significantly (like a hose completely disconnecting), you may see both codes as the system tries to diagnose the leak size.
• P0496 — P0496 indicates 'EVAP Flow During a Non-Purge Condition,' which almost always points directly to a faulty purge valve that is stuck open. It's very common to see this code alongside P0442 on the Encore and its platform mates. Seeing both codes makes the purge valve the primary suspect.

Technical Service Bulletins (TSBs) & Recalls

• 21-NA-124: Provides diagnostic tips for EVAP leaks related to P0442 and P0455.
• PIT4943D: Directs technicians to a May 2013 Techlink article about using an EVAP system tester for P0442 diagnosis.

Platform-Specific Known Issues

• Difficulty Starting After Refueling: A very common symptom reported by Encore and platform-mate owners is a rough idle, stumbling, or extended crank time right after filling the gas tank. This is a classic sign of a purge valve stuck open, which floods the engine with fuel vapors. If you experience this symptom along with a P0442 (and especially a P0496), the purge valve is almost certainly the cause.
• Purge Valve Is The Overwhelmingly Common Culprit: Across owner forums and repair videos for the Buick Encore, Chevy Cruze, and Trax, the vapor canister purge valve (GM Part #55573017) is the most cited fix for a P0442 code, especially when P0496 is also present. Many owners report successfully replacing this part themselves in under 30 minutes with basic tools.

Mechanic-Grade Diagnostic Values

• EVAP Canister Vent Valve Solenoid Resistance — expected: 20 - 50 Ohms. Failure: A reading of 0 or infinite (Open Line) indicates a failed coil. A reading outside the 20-50 Ohm range suggests a faulty solenoid.
• EVAP Service Bay Test Prerequisites (GM Scan Tool) — expected: Fuel Level: 15-85%, Engine Coolant Temperature: Below 158°F (70°C). Failure: The test will not initiate if these conditions are not met, preventing forced diagnosis in the shop.

Hidden / Shadow Codes Worth Checking

• Mode 10 DTCs (Permanent Codes): After a repair is made and the code is cleared with a scan tool, a permanent version of the code is stored in 'Mode 10'. This permanent code will only be fully erased by the PCM after the vehicle completes a set number of warm-up cycles (e.g., 40) without the fault reoccurring. (see via Advanced OBD-II scan tools with Permanent DTC support.)

Scan Tool Commands That Help

• GM Tech 2 / GDS2: EVAP Service Bay Test — This function allows a technician to command the vehicle's ECM to run the entire EVAP leak self-test while in the service bay, without needing to perform a full drive cycle. It's used to verify a leak exists and to confirm a repair was successful.
• Bi-directional Scan Tool: EVAP Purge/Vent Solenoid Command — Allows the user to manually command the purge valve open (by percentage) or the vent valve closed. While commanding the valve, the technician can monitor the Fuel Tank Pressure (FTP) sensor to see if the system holds a vacuum, confirming valve operation.

Wiring & Ground Locations

• EVAP Vent Valve Wiring — Connector at the EVAP vent valve, located near the charcoal canister under the rear of the vehicle.. It is common for one wire to have 12V power with the key on, while the ECM provides a pulsed ground to activate the valve. A loss of power or a break in the ground control wire will prevent the valve from closing during the EVAP test, causing a leak code.
• Purge Valve Connector — On top of the engine, connected to the purge valve solenoid.. The connector itself or its wiring can become brittle and fail. Aftermarket pigtail connectors are available, indicating this is a known failure point that can mimic a failed valve.

Real Owner Repair Stories

• GM Forum user (Buick with P0442 (similar GM EVAP system)) — Persistent P0442 Check Engine Light.
  ❌ Tried (didn't work) Replaced vapor canister purge valve, Replaced canister vent solenoid
  ✅ What actually fixed it The fuel pump 'sending unit' gasket was leaking. The user discovered a gasoline smell inside the car when accessing the fuel tank pressure sensor, which is located at the same access point. Replacing the gasket resolved the fuel smell and the P0442 code.
• Reddit user in r/BuickEncore (2017 Buick Encore) — EVAP system issue (likely P0496 and/or P0442).
  ❌ Tried (didn't work) Took to mechanic who could not pinpoint the specific issue.
  ✅ What actually fixed it The issue was likely the purge valve, which is covered under a GM 'Special Coverage' program for certain model years (10-15 years or 120k-150k miles). The advice was to take it to a dealership to check for warranty coverage before paying for a repair.
• 2CarPros forum user (2000-2005 Mitsubishi Eclipse (demonstrates a universal component failure)) — Persistent P0442 code and visible fuel leak around the filler neck only when pumping gas.
  ❌ Tried (didn't work) Initial diagnosis was inconclusive.
  ✅ What actually fixed it The metal fuel filler neck was completely rusted out on the bottom, causing a leak. Replacing the entire fuel filler neck assembly fixed both the visible fuel leak and the P0442 code.

"I Checked Everything" — The Actual Cause

• In one documented case for a similar GM vehicle, a persistent P0442 was not resolved by replacing the common purge and vent valves. The actual cause was a leaking fuel pump sending unit gasket located under the rear seat/trunk floor. This type of leak may not be found with a standard smoke test and was only discovered because of a distinct fuel smell inside the car's cabin.

When the Usual Fixes Don't Work

• While the purge valve and gas cap are the most common culprits, do not assume they are the only cause. In a documented repair, a Buick owner replaced both the purge valve and the vent solenoid without fixing a P0442 code. The ultimate solution was replacing a leaking fuel pump sending unit gasket, a part that is not typically considered a primary suspect for this code. This highlights the importance of a thorough diagnosis, especially if a fuel smell is present inside the vehicle.

OEM Part Supersession History

• 55573017 → 55573017 (current) — This remains the primary OEM part number for the purge valve on the 1.4L engine.
  Heads up: Be aware that GM parts catalogs may show other purge valve part numbers for the 'Encore' (e.g., 12632174, 12666845). These may be for different engines or model years (like the newer Encore GX). Always verify the part number against your vehicle's VIN to ensure you get the correct part for the 1.4L engine.

Model Year Variations Within This Range

• 2016-2018: Certain 2016-2018 Encore models are covered by GM Special Coverage N192210240, which extends the warranty on the vapor canister purge valve to 10 years or 120,000 miles.
• 2020: Certain 2020 Encore models with the 1.4L LUV engine are covered by GM Special Coverage N232395300, which extends the warranty on the vapor canister purge valve to 15 years or 150,000 miles.