P0455 on 2015-2019 GMC Yukon Denali: EVAP Large Leak Causes and Fixes

What's Unique About the 2015-2019 Gmc YUKON DENALI

The 2015-2019 GMC Yukon Denali and its K2XX platform mates (Tahoe, Suburban, Escalade) use a capless fuel filler system. Unlike older models with a traditional gas cap, a common failure point is the spring-loaded flap in the filler neck, which can get stuck or fail to seal properly due to debris or wear. Additionally, the EVAP purge valve solenoid located on the driver's side of the intake manifold is a frequent failure item on this platform, sometimes getting stuck open and causing the system to fail its pressure test, which the computer interprets as a large leak.

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 'Tighten Gas Cap' message may appear on the driver information center, even though there is no cap.
• Possible faint fuel smell, especially near the rear of the vehicle.
• Remote start feature may be disabled while the Check Engine Light is active.
• In rare cases, difficulty starting immediately after refueling if the purge valve is stuck open.

Most Likely Causes

1. Faulty EVAP Purge Valve Solenoid 🔴 High Probability This valve is located on the engine's intake manifold and cycles frequently. Over time, it can get stuck open, creating a constant leak that the computer detects as a P0455. This is a very common failure on GM trucks and SUVs of this era.
   How to confirm: Remove the purge valve from the intake manifold. With no power applied, try to blow through it. If air passes through, the valve is stuck open and faulty. Alternatively, with the engine running, disconnect the electrical connector and the hose leading to the canister; if you feel any vacuum on the valve's port with your finger, it's stuck open and needs replacement.
   Typical fix: Replace the purge valve solenoid. It is located on the driver's side of the intake manifold, held on by one 8mm or 10mm bolt, and is easily accessible after removing the engine cover. 🎬 Watch: Quick walkthrough of the purge solenoid replacement.
   Est. part cost: $25-$60
2. Faulty Capless Fuel Filler Neck 🟡 Medium Probability The 2015+ models use a capless system. The internal spring-loaded flap can weaken or get stuck by dirt or debris, preventing a proper seal after refueling.
   How to confirm: Visually inspect the flap for debris or damage. Use the emergency funnel provided with the vehicle to gently work the flap open and closed, then clean the sealing surface with a clean rag. If the code returns, a smoke test is the next step.
   Typical fix: First, try cleaning the filler neck flap thoroughly. If the problem persists, the entire fuel filler neck assembly needs to be replaced. The GM part number is often 84017345.
   Est. part cost: $70-$150
3. Faulty EVAP Vent Solenoid 🟡 Medium Probability Located near the spare tire and charcoal canister, this valve is exposed to road grime, moisture, and debris, which can cause it to fail or get stuck open, preventing the system from sealing during its self-test.
   How to confirm: A bidirectional scan tool can command the valve to close. A smoke test is then performed; if smoke exits the vent valve's filter, it has failed. It can also be removed and tested by applying a 12V power source to see if the solenoid clicks and actuates.
   Typical fix: Replace the EVAP vent solenoid. This often requires dropping the spare tire 🎬 See how to replace the rear vent solenoid. for access. Be careful with the plastic electrical connector clip, which can be brittle.
   Est. part cost: $30-$75
4. Cracked or Disconnected EVAP Hose ⚪ Low Probability Rubber and plastic lines can become brittle over time due to heat and age, leading to cracks or loose connections, particularly at connection points to the valves or canister.
   How to confirm: A thorough visual inspection of all EVAP lines from the engine bay to the fuel tank is the first step. The definitive method is to perform a smoke test, which will make any leak visible as smoke will escape from the crack or loose fitting.
   Typical fix: Replace the damaged section of hose or reconnect it securely.
   Est. part cost: $10-$50

Rare But Worth Checking

• Cracked EVAP Charcoal Canister: The canister itself can develop cracks from road debris impact or age, creating a large leak. This is usually found during a smoke test after other common components have been ruled out.
• Leaking Fuel Tank Pressure Sensor: The sensor that monitors system pressure can develop a leak in its seal or housing. This is uncommon but possible and would be identified with a smoke test. In some cases, the sensor fails to register a pressure change, leading the computer to incorrectly assume there is a large leak.
• Leaking Fuel Pump Module Gasket: The large O-ring that seals the fuel pump assembly to the top of the fuel tank can degrade or become dislodged, creating a large leak. This is often the last part to be checked and is definitively found with a smoke test. One forum user reported this as the final fix after replacing all other common EVAP parts.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0455 is the active code.
2. Inspect the capless fuel filler neck. Use the vehicle's emergency funnel to check the flap's operation and clean any visible debris from the sealing surface with a clean cloth.
3. Clear the code and drive the vehicle for a few days to see if the light returns. The EVAP monitor runs under specific conditions, so it may take several drive cycles.
4. Visually inspect the EVAP purge solenoid on the driver's side of the engine's intake manifold and its connecting hoses for any obvious cracks or damage.
5. Test the purge solenoid. With the engine off, remove the valve and try to blow air through it. If air passes, it is stuck open and must be replaced. This is the most common failure.
6. If the purge valve is good, visually inspect the EVAP vent solenoid and charcoal canister located near the spare tire for any visible damage or corrosion.
7. The most effective next step is to perform a smoke test. This involves introducing low-pressure smoke into the EVAP system's service port (often near the purge valve). Smoke will exit from the location of the leak, making it easy to identify 🎬 Watch: How to find leaks using a smoke tester. cracked hoses, a faulty vent valve, a bad filler neck seal, or a leaking canister.

Parts You'll Likely Need

• EVAP Canister Purge Valve Solenoid (OEM #12690512 (supersedes 12610560; may be replaced by 12737252)) — This is a very common failure point on GM trucks and SUVs. It gets stuck open, causing the computer to register a large leak. It's often the first part to check and replace.
  Trusted brands: ACDelco, Standard Motor Products, Dorman
  OEM price range: $35-$50
  Aftermarket price range: $25-$40
• EVAP Canister Vent Valve Solenoid (OEM #23481275) — Its location near the rear axle exposes it to the elements, leading to corrosion and failure. It gets stuck open, preventing the system from sealing for its self-test.
  Trusted brands: ACDelco, Dorman
  OEM price range: $40-$60
  Aftermarket price range: $30-$50
• Fuel Tank Filler Neck (Capless) (OEM #84017345) — The internal sealing flap can fail or get clogged with debris, preventing a seal and causing a large leak code. Cleaning is the first step, but replacement is often necessary if the seal is worn.
  Trusted brands: GM Genuine Parts
  OEM price range: $70-$150
  Aftermarket price range: $50-$100

Related Codes That Often Appear With This One

• P0442 — P0442 is for a small EVAP leak. A component that is beginning to fail might initially cause a P0442 before the leak becomes large enough to trigger a P0455. The NHTSA TSB #21-NA-124 also groups these two codes together for diagnosis.
• P0449 — This code specifically points to a malfunction in the EVAP vent solenoid valve control circuit. If the vent valve is the cause of the P0455, it may be accompanied by a P0449.
• P0496 — This code indicates 'EVAP Flow During a Non-Purge Condition,' which almost always points directly to a faulty purge valve that is stuck open or leaking. If you see P0496 along with P0455, the purge valve is the most likely culprit.

Technical Service Bulletins (TSBs) & Recalls

• 21-NA-124: Provides diagnostic tips for testing EVAP leaks causing P0442 and/or P0455. It emphasizes checking connections and lines before condemning parts.

Platform-Specific Known Issues

• GM issued Technical Service Bulletin (TSB) #21-NA-124 which provides diagnostic tips for technicians to find EVAP leaks related to codes P0442 and/or P0455 on these vehicles. It advises a systematic check of lines and connections before replacing valves.

Mechanic-Grade Diagnostic Values

• EVAP Purge Valve Solenoid Resistance — expected: 30 to 38 Ohms (when cool). Failure: A reading outside this range, or infinite (OL), indicates a faulty coil.
• EVAP Vent Valve Solenoid Resistance — expected: 20 to 50 Ohms. Failure: A reading of 0 Ohms (short) or infinite/OL (open) indicates a failed solenoid coil.
• Fuel Tank Pressure (FTP) Sensor Voltage (Key On, Engine Off, system at atmospheric pressure) — expected: Approximately 1.45V - 1.5V. Failure: Voltage is stuck, does not change when vacuum is applied, or is significantly different from 1.5V at rest. A reading greater than 1.5V indicates vacuum, while less than 1.5V indicates pressure.

Scan Tool Commands That Help

• GDS2 / Tech2: EVAP Service Bay Test — This is a guided functional test that simulates driving conditions to verify the integrity of the entire EVAP system. It commands valves and monitors sensors to confirm a pass or fail, and is used to verify a repair is complete.
• GDS2 / Tech2: EVAP Purge/Seal — This command seals the system by closing the vent valve and then opens the purge valve to apply engine vacuum. By monitoring the FTP sensor, a technician can quickly determine if the system can hold a vacuum, identifying if a leak is present.
• GDS2 / Tech2: Vent Solenoid Control (On/Off) — This allows a technician to manually command the normally-open vent valve to close. This is a critical step before performing a smoke test to ensure the system is sealed. If smoke exits the vent while it's commanded closed, the valve is faulty.

Wiring & Ground Locations

• EVAP Vent Solenoid — On 2014-2019 models, it is located underneath the driver's side of the truck, right under the driver's door area, attached to the charcoal canister.. This is the physical location of a primary failure component. Knowing where to find it is essential for visual inspection, testing, and replacement.
• EVAP Vent Solenoid Power/Ground — At the vent solenoid connector, the power wire is typically Red/White. The control wire (ground side switched by the PCM) is White. Power is supplied via the #34 10-amp fuse in the fuse block.. If a P0449 (Vent Solenoid Circuit Malfunction) is present with P0455, testing for power at this connector is a key step. A lack of power could indicate a blown fuse or wiring issue, not a failed solenoid.

"I Checked Everything" — The Actual Cause

• In some cases, a smoke test may not reveal a leak, but the code persists. This can happen if the Fuel Tank Pressure (FTP) sensor is faulty. The sensor may not be physically leaking smoke, but it might be sending incorrect voltage readings to the computer, causing the ECM to believe a large leak exists when one does not.

OEM Part Supersession History

• 12610560 → 12690512, which may now be superseded by 12737252 — Standard part evolution and potential design improvements for the EVAP Canister Purge Valve.

Model Year Variations Within This Range

• 2015-2019 (K2XX Platform): This entire generation uses a capless fuel filler system, making the filler neck assembly a potential failure point not present on earlier models with a traditional gas cap. The EVAP system was also redesigned from the previous generation (GMT900), with different part numbers and locations for the purge and vent valves.