Theory of Operation

WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The Variable Geometry Turbocharger (VGT) adjusts turbocharger performance by moving the position of the impeller nozzle, on the high-pressure (engine exhaust gas) side of the turbocharger assembly. Desired position of the actuator is commanded from the Powertrain Control Module (PCM). Actual position is sensed by the VGT, and reported back to the PCM as feedback. Discrepancy in position feedback sent to the module, and commanded position sent to the VGT by more than a prescribed amount will result in failure of device rationality diagnostics. Failure to properly actuate the VGT will result in poor engine performance. The PCM lights the MIL lamp after the diagnostic runs and fails in two drive cycles. The PCM will turn off the MIL lamp immediately after this diagnostic runs and passes in four consecutive drive cycles.