Trouble code P0455 is probably one of the most common trouble codes encountered out in the wild, since something as simple as forgetting to tighten the gas cap enough will set this diagnostic trouble code (DTC).
In this tutorial, which I've written specifically for the 2003-2013 Chevy Express/GMC Savana with a 4.8L, 5.3L, or 6.0L engine, I'll walk you through the meaning of code P0455 and the most common fixes to make this DTC go away.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- Chevrolet Express 1500, 2500, 3500: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013.
- GMC Savana 1500, 2500, 3500: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013.
What Does Trouble Code P0455 Mean?
When your van's computer detects a big leak somewhere in the evaporative emissions (EVAP) system, which is responsible for controlling the gasoline fumes from your fuel tank so they don't escape into the atmosphere and contribute to pollution, it'll set the following trouble code:
- P0455: Evaporative Emission Control System Leak Detected (Gross Leak/No Flow).
For the most part, when the P0455 DTC is triggered, you usually don't notice any obvious symptoms besides the check engine light turning on.
To get an idea of how to approach diagnosing this DTC, it's important to know that the gasoline in the fuel tank likes to evaporate. Gasoline is so volatile, that it'll start to evaporate at room temperature. Even when your gas tank is closed up tight, some of the gasoline inside is slowly evaporating and turning into vapor.
If nothing is done about these fuel vapors, they would just escape into the air, contributing to pollution. But the EVAP system captures those vapors and stores them temporarily.
It does this using a network of hoses, solenoid valves, and a charcoal canister. The charcoal canister is like a big sponge that absorbs the fuel vapors. Then, when conditions are right, like when you're driving and the engine is warmed up, the system purges those vapors back into the engine, where they can be burned off harmlessly.
The EVAP system is designed to be airtight and keep those fuel vapors contained. But if something goes wrong, like a hose develops a crack or a solenoid valve gets stuck open, then those vapors can escape into the atmosphere.
When that happens, your van's onboard computer (Powertrain Control Module - PCM), senses that something's amiss. It runs checks on various systems, including the EVAP system, and if it detects a leak, it'll set off a P0455 trouble code.
Since your van's onboard computer (Powertrain Control Module - PCM) is continually running checks on various systems, including the EVAP system, and if it detects a leak, it'll set off a P0455 trouble code
What Causes Trouble Code P0455?
The EVAP system is quite complex, involving hoses, a charcoal canister, a vent solenoid valve, and a purge solenoid valve, among other components. So quite a few things, when they fail or develop a leak, can trigger the PCM to set a P0455 DTC.
On the Chevy Express or GMC Savana vans, the most common cause of the P0455 code, which points to a large leak in the evaporative emission control system (EVAP), is actually something pretty simple: a loose or missing gas cap. This might sound a bit too easy to be true, but tightening up or replacing a gas cap is often all it takes to fix the issue.
Besides the gas cap, other possible causes include:
- Faulty or damaged gas cap: This is super common. The gas cap keeps the fuel system sealed tight. If it's not doing its job, you'll get those vapors escaping.
- EVAP hoses/lines issues: These hoses can get cracked, loose, or worn out over time. Any damage here can lead to leaks in the system.
- EVAP Carbon Canister: If the canister is cracked or damaged, it can cause leaks. It's designed to store those fuel vapors, so any issues here lead straight to an EVAP diagnostic trouble code.
- EVAP Purge Solenoid failure: This valve controls when those captured vapors are sucked (purged) into the intake manifold. If it's stuck open, it can mess up the whole system's pressure.
- EVAP Vent Solenoid failure: This part lets fresh air flow into the EVAP system. If it's stuck open, it'll lead to the PCM notifying you of an EVAP system leak detection.
- Leaking fuel tank or filler neck: Less common, but still a possibility. Any physical damage here can lead to significant vapor leaks.
How To Resolve Trouble Code P0455
Pinpointing the exact issue of the EVAP system leak requires some visual inspections and some testing. There is a method to the madness and it all starts by visually checking a few things:
- Check the Gas Cap: As we discussed earlier, a loose, damaged, or missing gas cap is often the culprit. So, start by making sure the gas cap is properly tightened and that the rubber seal is in good condition. If not, replacing the gas cap with a new one should do the trick.
- Inspect EVAP System Components: If the gas cap checks out okay, it's time to inspect the other components of the EVAP system. This includes hoses, valves, and the charcoal canister. Look for any cracks, leaks, or damage. Sometimes a visual inspection is all it takes to spot the problem.
- Smoke Test: If you can't find the leak just by looking, a smoke test can help. This involves using a smoke machine to pump smoke into the EVAP system and then looking for where it's leaking out. Professional auto repair shops use this method to pinpoint hard-to-find leaks.
- Check Fuel Filler Neck: The fuel filler neck, where you insert the gas pump, can also develop leaks over time. Inspect it for any signs of damage or corrosion.
- Test Purge Solenoid and Vent Solenoid: The purge valve and vent valve are responsible for controlling the flow of vapors in the EVAP system. Testing these valves to ensure they're functioning properly can help diagnose the issue.
- Inspect Fuel Tank: In some cases, the fuel tank itself could be damaged or corroded, leading to a leak. If all else fails, it may be necessary to inspect the fuel tank for any signs of damage.
- Clear the Code: Once you've identified and fixed the problem, you'll need to clear the trouble code from the van's computer. You can do this using an OBD-II scanner or by disconnecting the battery for a few minutes.
Solving a diagnostic trouble code P0455 involves a systematic process of elimination. You'll want to start with the most obvious and basic checks, and then move up to testing the more 'complicated components'.
What Tools Do I Need?
Here's a list of the basic tools you'll need:
- OBD-II Scanner: An OBD-II scanner is a must-have tool for reading diagnostic trouble codes (DTCs) stored in your vehicle's onboard computer (PCM). You can use the scanner to retrieve codes like P0171 and P0174, as well as view live data, which can provide valuable information about engine parameters such as fuel trims, oxygen sensor readings, and more.
- Multimeter: A multimeter is a versatile tool that can be used to test sensors for proper operation and continuity of electrical circuits.
- Smoke Machine or Propane/Starting Fluid: While not essential, a smoke machine or propane/starting fluid can be helpful for diagnosing vacuum leaks. A smoke machine is used to introduce smoke into the intake system to detect leaks. It's a much safer process than using propane or starting fluid to check for vacuum leaks.
- Basic Hand Tools: You'll also need standard hand tools like screwdrivers, pliers, socket set, and wrenches may also be necessary for performing various tests and repairs.
The affordability of smoke machines has become a game-changer for the DIYer in diagnosing a hard-to-find EVAP system leak for the DIYer!
More Chevy Express/GMC Savana Articles And Tutorials
You can find a complete list of articles and diagnostic tutorials for the V8 Chevy Express and GMC Savana here:
Here's a sample of the tutorials you'll find in the index:
- How To Test For The Fuel Pump (2008-2013 V8 Chevy Express, GMC Savana).
- How To Test For A Blown Head Gasket (2003-2013 V8 Chevy Express, GMC Savana).
- How To Diagnose An Engine Cranks But Does Not Start Problem (2003-2007 V8 Chevy Express, GMC Savana).
- How Can I Tell If The Automatic Transmission Is Bad? (2003-2013 Chevrolet Express, GMC Savana).
If this info saved the day, buy me a beer!
