I have a 2013 Lexus ES350 With 80k. It starts right up and never has any problems (besides what I consider a rough idle in Drive). No matter how many times I clear that P1604 code, it comes back instantly. Apparently it is set when there is no fuel in the tank or it fails to start properly but I have not had any issues with starting and keep my tank mostly full. Not sure what’s going on. Any ideas? Thanks.

 

Check battery and charging system first. Clean cables and connection to battery.

https://www.autocodes.com/p1604_lexus.html

 

Thank you. Terminal is clean as a whistle and a brand new battery (diehard platinum) was put in last month. So, unfortunately not it

 

Wondering if it might be related to the fuel filter, fuel vapour recovery system including charcoal canister & extraction "fan", or even fuel filler cap sealing.

 

Try Seafoam in the gas tank?