2009 Dodge Charger 3.5L V6: U0101, PO609, P0420 Fault Codes Cause Limp Mode and Low Speed Limitation

Make: Dodge Model: Charger Year: 2009 Engine: V6, 3.5L Error Codes: U0101, PO605, P0420 I own a 2009 Dodge Charger 3.5L Police Package with no prior issues until recently. The vehicle began exhibiting intermittent limp mode behavior where it is forced into a low gear and only reaches speeds of 20 to 30 mph. During these episodes, the check engine light illuminates with a flashing red dot, and the ESP/BAS system activates with a 'slippery when wet' warning. The car must be warmed up for 15–30 minutes before driving becomes possible. After warming up adequately, it typically operates normally. However, the limp mode may return unexpectedly, requiring a restart to resolve. I have already performed several troubleshooting steps: replaced the ECU, installed a new battery, completed a full transmission fluid change, checked all fuses, and applied Lucas No-Slip treatment. Despite these efforts, the issue persists. The error codes U0101 (Vehicle Speed Sensor Communication Issue), PO605 (Transmission Control Module Circuit Fault), and P0420 (Catalyst Efficiency Below Threshold) are now consistently detected in the OBD-II system. I am researching solutions for these specific fault codes, particularly how they may interact to cause limp mode behavior. Any insights or recommendations on diagnosing or resolving this combination of error codes in a 2009 Dodge Charger 3.5L would be greatly appreciated.