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
(W527) VSIM CAN B BUS (+) CIRCUIT SHORTED TO VOLTAGE
(W528) VSIM CAN B BUS (-) CIRCUIT SHORTED TO VOLTAGE
MULTI-PURPOSE MODULE (POLICE AND TAXI INTERFACE MODULE-PTIM)