Operation CHARM: Car repair manuals for everyone.

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 (PCSV) open which allows the fuel vapors to be pulled into the intake manifold from the canister. This valve is normally closed (NC) and is opened by the ECM. The Purge valve received B+ to one terminal and the ECM will apply ground to the other terminal to open the valve.

DTC Description

If there is Open in PCSV circuit, ECM sets DTC P0444.

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 on the scope 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.