850 L5-2.3L Turbo VIN 57 B5234FT (1994)
Turbocharger Control Module: Description and Operation
Turbocharger Control
PURPOSE
The Turbocharger control system regulates boost pressure to ensure optimum performance throughout the engines normal operating range. Since
boost pressure is electronically controlled, the turbocharger delivers full output at speeds as low as 2000 RPM.
OPERATION
The ECM controls boost pressure via the turbocharger control valve.
Turbocharger Control Valve
Turbocharger Control Valve
The wastegate valve, and hence boost pressure, is controlled by the turbocharger control valve. The ECM supplies the control valve with a
pulsating signal (duty cycle) which can be varied to control the pressure delivered to the wastegate.
When the ECM determines that higher boost is needed, the duty cycle increases allowing a certain amount of boost pressure to be diverted from
the wastegate signal hose. Since this reduces the signal, wastegate opening is delayed and boost is increased.
The ECM uses signals from the following sensors to determine boost pressure:
- Throttle Position Sensor
- Mass Air Flow Sensor
- RPM Sensor
NOTE: Boost pressure is not determined by a pressure sensor, but by the Mass Air Flow Sensor.
