Theory of operation
WARNING: This page is about a different car, the 2011 RAM Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The Fuel Pump control is requested by the Powertrain Control Module (PCM) along the Fuel Pump control relay circuit. The Totally Integrated Power Module (TIPM) monitors the sense voltage on the Fuel Pump relay circuit, when PCM pulls the circuit low the TIPM engages the Fuel Pump. If the sense voltage is open or pulled low the PCM will set the P0627-FUEL PUMP RELAY CIRCUIT DTC.