I have good news and bad news for you. Yes, you are correct. It is your fuel tank sending unit that is failing and causing this problem. The bad news is that P0446 is not related to it and fixing it will not take the DTC away. Good news again, I have included instructions for you in the diagrams down below, how to remove, replace, and install the fuel pump assembly and the fuel sending unit. Please use these instructions to fix your vehicle's fuel level issue and get to us with what you find out.
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Wednesday, March 13th, 2019 AT 7:32 PM