Firebird V8-305 5.0L VIN E (1992)
Pressure Operated Electric Divert/Switching Valve (PEDES): Description and Operation
A.I.R. System Control (PEDES) Valve
The diverting and switching functions are electronically controlled by the ECM, which grounds the circuit to energize the solenoid. Self-generated
pressure from the A.I.R. pump is used to operate the valve, which is independent of manifold vacuum.
When the engine is cold ("Open Loop"), the port solenoid is energized and air pump pressure opens the passage to the exhaust ports. During normal
operation ("Closed Loop"), the port solenoid is de-energized, the converter solenoid is energized, and air pump pressure opens the passage to the
catalytic converter. When the ECM determines that air divert is necessary, both solenoids are de-energized and air pump output is diverted to the
atmosphere through a divert/relief valve. The divert/relief valve limits system pressure.
Air is diverted to the atmosphere under the following conditions:
1.
Rich operation.
2.
When the ECM recognizes a problem and flashes the "SERVICE ENGINE SOON" Light.
3.
During deceleration
4.
During high engine speed operation when air pressure is greater than the setting for the internal relief valve.
