If DTCs 00545/00638 are stored on a 2003 Passat Sedan 4Motion, the problem may be caused by:
Incorrect Engine Control Module (ECM) coding (codeable ECM only);
Wiring harness and/or connections between the Transmission Control Module (TCM) and ECM;
Intermittent continuity in the engine harness.
Poor engine compartment ground (GND).
If the vehicle exhibits this condition, use the table as a guide for repairs. Erase the DTC memory, road-test the vehicle and recheck for any stored DTCs.
Courtesy of ALLDATA.