Theory Of Operation

The Turbocharger Speed Sensor is a variable reluctance speed sensor. It consists of a coil of wire and an iron core. The target on the turbocharger shaft is a ground flat surface in the center of the shaft. As the flat surface on the turbocharger shaft spins past the speed sensor, a signal is generated. The Powertrain Control Module (PCM) interprets this signal and converts it to a turbocharger speed reading. The PCM will illuminate the Malfunction Indicator Lamp (MIL) after the diagnostic runs and fails in two consecutive drive cycles. During this time the PCM uses an estimated turbocharger speed. An engine power derate may be experienced. The PCM turns off the MIL when the diagnostic runs and passes in four consecutive drive cycles.