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 Smart Power Relay supplies 12 Volts to the Mass Airflow Sensor, the Exhaust Gas Recirculation (EGR) Airflow Control Valve and the Variable Geometry Turbocharger. The Smart Power Relay Control circuit is a low side driver controlled by the Powertrain Control Module (PCM). The Smart Power Relay is powered up at key on, and remains powered until just after key off. The power supply to the Smart Power Relay is wired directly from the Totally Integrated Power Module (TIPM). The PCM will illuminate the Malfunction Indicator Lamp (MIL) and disable the regeneration mode immediately after this diagnostic runs and fails. During this time there will likely also be voltage supply faults for the Mass Airflow Sensor, the EGR Airflow Control Valve and the Variable Geometry Turbocharger. The PCM will turn off the MIL once the diagnostic runs and passes in four consecutive drive cycles.