How to Fix Error Code P0118 on a 2013 Audi A4 Quattro?

It sounds like you're dealing with a persistent issue after replacing your water pump and temperature sensor. Since the check engine light came back on even after clearing the codes, it's a good idea to start by checking the connections. Make sure the ECT connector is properly seated and that the wires are intact. You mentioned that you have a blue wire with white stripes and a brown wire with white stripes coming from the ECM to the ECT connector. While I can't specify which is positive or negative, following the same wiring sequence as the old connector should help. If you're still not getting a 5V reference and instead seeing higher voltages like 12V or more, that could indicate a problem. It’s also worth checking for any open circuits between the ECT sensor and the PCM. If everything looks good there, try disconnecting the negative battery terminal for about five minutes again. After reconnecting, turn the ignition on and off five times without starting the engine, then start the car and let it run for about 15 minutes to see if the error persists. If the check engine light continues to come on despite these steps, it might be time to consider having the ECM checked. It’s possible that the ECM itself could be faulty, especially since you’ve already replaced the relevant components and followed the troubleshooting steps. Visiting a qualified mechanic who can perform a thorough diagnostic on the ECM would be a wise next step.