Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2002EXPRESS 1/2 TON VAN V8-5.7L VIN RREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTEMISSION CONTROL SYSTEMSDESCRIPTION AND OPERATIONEVAPORATIVE EMISSION (EVAP) CONTROL SYSTEMEVAP SYSTEM COMPONENTS
2002 Chevrolet Express 1/2 Ton Van V8-5.7L VIN R
EVAP System Components
2002 Chevrolet Express 1/2 Ton Van V8-5.7L VIN RSECTION EVAP System Components
EVAP SYSTEM OVERVIEW
The EVAP canister is a sealed unit with 3 ports.
^ Purge pipe
^ Vapor pipe
^ Vent pipe
The canister is filled with carbon pellets used to absorb and store fuel vapors. Fuel vapor is stored in the canister until the control module determines that the vapor can be consumed in the normal combustion process.
EVAP PURGE VALVE
The EVAP purge valve controls the flow of vapors from the EVAP system to the intake manifold. This normally closed valve is pulse width modulated by the control module to precisely control the flow of fuel vapor to the engine. The valve will also be opened during some portions of the EVAP testing, allowing engine vacuum to enter the EVAP system.
EVAP VENT VALVE
The EVAP vent valve controls fresh airflow into the EVAP canister. EVAP valve is normally open. The control module will command the valve closed during some EVAP tests, allowing the system to be tested for leaks.
FUEL TANK PRESSURE SENSOR
FTP sensor measures the difference between the pressure or vacuum in the fuel tank and outside air pressure. The control module provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the control module that can vary between 0.1 - 4.9 volts. As fuel tank pressure increases, FTP sensor voltage decreases, high pressure = low voltage. As fuel tank pressure decreases, FTP voltage increases, low pressure or vacuum = high voltage.
EVAP SERVICE PORT
The EVAP service port is located in the EVAP purge pipe between the EVAP purge valve and the EVAP canister. The service port is identified by a green colored cap.
EVAP PRESSURE/PURGE DIAGNOSTIC STATION
The J 41413 EVAP Pressure/Purge Diagnostic Station is used to help locate leaks in the EVAP system. The station provides a clean, dry, regulated supply of nitrogen to pressurize the EVAP system. Refer to the directions on the cart for proper operation. The J 41415-40 Fuel Tank Cap Adapter is used to adapt the J 41413 to the fuel filler neck. Pressurizing the EVAP system at the fuel filler neck allows testing of the filler neck and the fuel fill cap on vehicles with Onboard Refueling Vapor Recovery (ORVR).
The J 41416 Ultrasonic Leak Detector is then used to pinpoint the source of the leak.
EVAP System Overview:
EVAP Canister:
The EVAP canister is a sealed unit with 3 ports.
^ Purge pipe
^ Vapor pipe
^ Vent pipe
The canister is filled with carbon pellets used to absorb and store fuel vapors. Fuel vapor is stored in the canister until the control module determines that the vapor can be consumed in the normal combustion process.
EVAP PURGE VALVE
The EVAP purge valve controls the flow of vapors from the EVAP system to the intake manifold. This normally closed valve is pulse width modulated by the control module to precisely control the flow of fuel vapor to the engine. The valve will also be opened during some portions of the EVAP testing, allowing engine vacuum to enter the EVAP system.
EVAP VENT VALVE
The EVAP vent valve controls fresh airflow into the EVAP canister. EVAP valve is normally open. The control module will command the valve closed during some EVAP tests, allowing the system to be tested for leaks.
FUEL TANK PRESSURE SENSOR
FTP sensor measures the difference between the pressure or vacuum in the fuel tank and outside air pressure. The control module provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the control module that can vary between 0.1 - 4.9 volts. As fuel tank pressure increases, FTP sensor voltage decreases, high pressure = low voltage. As fuel tank pressure decreases, FTP voltage increases, low pressure or vacuum = high voltage.
EVAP SERVICE PORT
The EVAP service port is located in the EVAP purge pipe between the EVAP purge valve and the EVAP canister. The service port is identified by a green colored cap.
EVAP PRESSURE/PURGE DIAGNOSTIC STATION
The J 41413 EVAP Pressure/Purge Diagnostic Station is used to help locate leaks in the EVAP system. The station provides a clean, dry, regulated supply of nitrogen to pressurize the EVAP system. Refer to the directions on the cart for proper operation. The J 41415-40 Fuel Tank Cap Adapter is used to adapt the J 41413 to the fuel filler neck. Pressurizing the EVAP system at the fuel filler neck allows testing of the filler neck and the fuel fill cap on vehicles with Onboard Refueling Vapor Recovery (ORVR).
The J 41416 Ultrasonic Leak Detector is then used to pinpoint the source of the leak.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.