WARNING: This page is about a different car, the 2010 Dodge Charger and 2010 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.
Possible Causes
(W538) FUEL LEVEL STATUS SIGNAL CIRCUIT OPEN OR SHORTED TO VOLTAGE
AFTERMARKET LIGHT/SIREN CONTROLLER
MULTI-PURPOSE MODULE (POLICE AND TAXI INTERFACE MODULE-PTIM)