General Information

Component Location





General Description

The purpose of the Evaporative Emission Control System is to capture the fuel vapors (HC) that would escape from the fuel system. Gasoline vapors from the fuel tank and throttle body are collected in a charcoal canister. When the engine is running, the ECM can command the purge valve open which allows the fuel vapors to be pulled into the intake manifold from the canister. To test the system, the ECM will close off the Canister Close Valve and then open the Purge valve. The Purge valve is then closed, trapping a vacuum in the Evaporative Emission Control. If this vacuum decays too quickly it indicates a leak in the system and the ECM will set a code. The FTPS is used for monitoring pressure and vacuum levels in the fuel tank during the purge cycle and leak checking.

General Description

If the Reference value of differential tank pressure is below -0.2 kPa, ECM determines that PCSV is Open stuck and sets DTC P0496.

DTC Detecting Condition





Specification





Diagnostic Circuit Diagram





Signal Waveform & Data




Fig. 1) Normal waveform of PCSV under control condition.
The Purge Control Solenoid Valve (PCSV) is normally closed and is opened by the ECM. When the PCSV is open, fuel vapors are pulled into the intake manifold from the charcoal canister. The control the flow of the fuel vapors, the ECM will pulse the ground to the Purge Valve. Because the scope is hooked to the ground side of the circuit, battery voltage is shown when the valve is not energized. Once the ECM completes the ground circuit, current starts to flow through the solenoid circuit. Because the solenoid is the load in the circuit, the voltage will drop across the solenoid. This can be seen as a drop from B+ to near zero volts. Once the ground circuit is opened by the ECM the magnetic field in the solenoid collapses causing an induced voltage in the circuit. This can be seen on the scope as a spike after the solenoid is de-energized.