1. Check the fuel injector circuit resistance at the valve cover gasket connectors first. To do this, disconnect the engine harness from the valve cover gasket. Check the resistance between the center pin (pin 5) and the two pins on either side of it. This will ohm all 4 injectors on each side of the engine. The resistance should be 2-4 ohms, and there should be no continuity to ground on any of the wires. 2. If circuit resistance is high, remove the valve covers and inspect Under Valve Cover (UVC) harnesses and connections. If there are connection problems, repair the connections and install a locking clip (part #2C3Z-14A163-AB) to hold the UVC harness to the valve cover gasket. 3. If the resistance is correct on the injectors, do the injector buzz test and listen for the injectors to buzz. If all circuit resistances are correct, but injectors do not buzz or are very weak sounding during the injector buzz test, most likely the Injector Driver Module (IDM) has failed.
If the IDM has failed and is setting both high side open codes, inspect the UVC harness connections even if the injectors ohm OK. If the connectors come loose intermittently, it can damage the IDM.