What would be solutions for trouble code PO231 and PO603 in a Cadillac Deville?

Trouble code PO231 indicates a fuel pump secondary circuit issue, while PO603 signifies a communication error with the engine control module (ECM). For PO231, check the fuel pump relay, wiring, and connections for damage or corrosion, and consider testing the fuel pump itself. For PO603, inspect the wiring and connectors between the ECM and various sensors, and ensure that the ECM is functioning properly, as it may require reprogramming or replacement. Addressing these issues systematically will help resolve the trouble codes.