Theory Of Operation

GENERAL WASTEGATE OPERATION:  The base Turbocharger boost pressure is managed by the Wastegate. The primary function of the Wastegate is to regulate the maximum boost pressure in a Turbocharged engine. The Wastegate Motor is electrically controlled by an internal H-Bridge Driver circuit inside the Powertrain Control Module (PCM). When the PCM determines boost is required, it energizes the Wastegate Motor to move the Wastegate toward the closed position. When less boost is needed the PCM energizes the Wastegate Motor to move the Wastegate toward the open position allowing the exhaust gases to bypass the turbine inside the Turbocharger. When not energized the Wastegate is in the open position. The PCM monitors the signal from the Wastegate internal position sensor to determine when the Wastegate has reached the commanded position.

WASTEGATE POSITION SENSOR:  The PCM detects the position of the Wastegate Valve from feedback provided by the Wastegate Position Sensor. The Wastegate Position Sensor is integrated as part of the Wastegate Valve and operates like a typical three wire sensor. The PCM provides a 5-Volt Supply and Sensor Return circuit to the Wastegate Position Sensor and receives the feedback voltage on the signal circuit.

GENERAL H-BRIDGE OPERATION:  An H-Bridge is an electronic circuit that enables a voltage to be applied across a load in either direction. The H-Bridge arrangement is generally used to reverse the polarity/direction of the DC motor which allows the DC motor to run forward and backwards. A DC Motor is typically controlled using an H-Bridge circuit inside the Powertrain Control Module (PCM). See the figure below for a general configuration and operation of an H-Bridge: 

Courtesy of CHRYSLER GROUP, LLC

An H-Bridge circuit is built with four solid-state switches. When the switches S1 and S4 are closed and S2 and S3 are open (left) a positive voltage will be applied across the motor. Opening S1 and S4 switches and closing S2 and S3 switches (right) will allow the motor to reverse operation.

DIAGNOSTICS: 

• The PCM performs diagnostics on the DC Motor and circuits. If the PCM detects that the current draw or Pulse Width Modulation (PWM) to the DC Motor is too high or low for a calibrated amount of time, then the PCM determines that the motor or circuitry is faulted and not operating properly.
• During operation the PCM performs a rationality diagnostic. The rationality diagnostic uses the feedback form the integrated Wastegate Position Sensor to monitor the difference between the desired position and the actual position of the Wastegate Valve.
• The PCM also performs diagnostics on the integrated Wastegate Position Sensor separately  to monitor the circuits for an open, shorted to voltage, or shorted to ground condition,