The logic module uses this solenoid to control the turbocharger wastegate actuator. There were two configurations used, depending which type of turbo charger was installed on the vehicle.
Vehicles equipped with a Garrett T03 turbocharger (1984 - 1987 Turbo I) or Garrett T04 turbocharger (1986 - 1990 Turbo II) used a system that switched the actuator between manifold pressure (when deactivated) and the atmosphere (when deactivated). While not in boost, the actuator is bled to the atmosphere. As boost begins to build, the logic module begins pulsing the solenoid to start pressurizing the actuator and open the wastegate. The logic module will adjust the duty cycle of the pulses to raise or lower the actuator pressure to open and close the wastegate as it sees fit. An orifice (restrictor) is present in the line between the actuator and the solenoid to "smooth-out" the changes in actuator pressure caused by the pulsing.
Vehicles equipped with the Mitsubishi TD04 turbocharger (1988 - 1993 Turbo I) used a system that was simply a bleed valve to the atmosphere and was closed when not activated. The source of manifold pressure is actually the turbocharger's compressor housing. This source leads to a T-fitting via an orifice (restrictor). From the fitting, a line goes to the actuator and the other to the solenoid. Some models also seem to have an orifice in the line between the fitting and the solenoid. While not in boost, the solenoid valve will be closed which causes pressure to build in the actuator when the system goes into boost. When the computer detects boost, it begins to pulse the solenoid to bleed-off some of that pressure. The computer will adjust the duty cycle of the pulses to raise or lower the actuator pressure to open and close the wastegate as it sees fit.
When the logic module is turning on or off the solenoid, it momentarily checks the output of the solenoid driver to see if it is responding the way it should. If it does not see about 0V when on (open circuit) or 12V when off (short circuit), a fault code 36 is stored.
|Return to the Engine Control Unit page|
Copyright © 1996-2003 Russ W. Knize.