A P0440: Evaporative Emission Control System Malfunction is probably one of the most commonly encountered trouble codes out there, since it's usually caused by a loose or missing gas cap.
In this tutorial, I'll shed some light on what this trouble code means and some of the tests you can perform to find its cause (and solution) in case a loose gas cap is not the source of the problem.
Contents of this tutorial:
You can find this tutorial in Spanish here: Código P0440 ¿Qué Significa? (1996-1999 3.8L V6 Buick, Chevrolet, Pontiac, Olds) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 3.8L Buick LeSabre: 1996, 1997, 1998, 1999.
- 3.8L Buick Park Avenue: 1996, 1997, 1998, 1999.
- 3.8L Buick Regal: 1996, 1997, 1998, 1999.
- 3.8L Buick Riviera: 1996, 1997, 1998, 1999.
- 3.8L Chevrolet Lumina: 1998, 1999.
- 3.8L Chevrolet Monte Carlo: 1998, 1999.
- 3.8L Oldsmobile 88 (Eighty-Eight): 1996, 1997, 1998, 1999
- 3.8L Oldsmobile 98 (Ninety-Eight): 1996
- 3.8L Oldsmobile Intrigue: 1998, 1999
- 3.8L Oldsmobile LSS: 1996, 1997, 1998, 1999
- 3.8L Oldsmobile Regency: 1997, 1998
- 3.8L Pontiac Bonneville: 1996, 1997, 1998, 1999
- 3.8L Pontiac Grand Prix: 1997, 1998, 1999
What Does Trouble Code P0440 Mean?
A P0440: Evaporative Emission Control System Malfunction means that fuel vapors are escaping into the atmosphere from the gas tank.
Unfortunately, this trouble code does not pinpoint a specific component as the cause of the EVAP system failure.
Common Symptoms Of A P0440 Trouble Code
A P0440 will cause the vehicle to fail an emissions test. Usually, that's it.
To be a bit more specific: A problem with the EVAP system generally does not cause any driveability issues, other than an illuminated check engine light on the instrument panel.
What Does The EVAP System Do?
The purpose of the evaporative emission control (EVAP) system is to capture the fuel tank vapors and prevent them from escaping into the ambient air (the atmosphere).
The EVAP system, on the 1996-1999 3.8L V6 vehicles, consists of:
- Fuel tank.
- EVAP vent solenoid.
- Fuel tank pressure sensor.
- Fuel pipes and hoses.
- Vapor lines.
- Gas cap.
- EVAP emission canister (charcoal canister).
- Purge lines.
- EVAP purge solenoid.
What Causes A P0440 Trouble Code?
In many cases, this trouble code appears after fueling the vehicle and not tightening the gas cap enough.
If the gas cap is nice and tight, the following can cause a P0440 trouble code to light up the check engine light:
- Damaged/incorrect gas cap.
- Damaged/leaking EVAP system hose.
- Bad canister purge control valve.
- Damaged/broken EVAP emission canister (charcoal canister).
- Damaged/leaking fuel tank.
- Leaking fuel tank hoses.
How To Diagnose And Repair A P0440 Trouble Code
Repairing a trouble code P0440 involves finding and replacing the component that is leaking fuel vapors into the atmosphere.
What is going to help you achieve this is a vacuum hose routing diagram (of your particular 3.8L V6 GM vehicle).
Thankfully, this vacuum house routing diagram is found in your vehicle's engine compartment.
To find the component causing the P0440 trouble code, I recommend the following tests:
- Visually inspect the gas cap for damage or a worn gasket.
- Visually inspect all EVAP system hoses for damage/fuel/vacuum leaks.
- Check the operation of the EVAP purge valve solenoid.
- Visually inspect the EVAP emission canister for damage.
Replace any component that is damaged.
In some cases, the fuel tank has to be lowered (and possibly removed) to check:
- Fuel lines: These are the fuel lines that connect to the fuel tank sending unit.
- EVAP system hose: This is the vapor hose/line that connects to the fuel tank sending unit (this hose/line is the one that carries the fuel vapors to the EVAP emission canister).
- Fuel tank sending unit gasket: This is the gasket that sits between the fuel sending unit assembly and the gas tank. Check it for cracks and/or damage.
- Fuel tank pressure sensor: This is the sensor that measures the fuel tank pressure and if there's any loss (of pressure) tells the fuel injection computer that there's a leak in the EVAP system.
- Fuel filler hose: This hose connects the fuel filler neck to the gas tank and has two hose clamps that should be check for looseness.
More 3.8L GM V6 Tutorials
You can find a complete list of 3.8L GM V6 tutorials in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test The MAF Sensor (GM 3.8L V6 1996-2005).
- How To Test A Does Not Crank Condition -Case Study (GM 3.8L).
- GM 3.8L Ignition Control Module And Crank (3X, 18X) Sensor Test.
- How To Test The Ignition Coil Pack -Misfire Troubleshooting Tests (GM 3.8L).
If this info saved the day, buy me a beer!
