Hello and welcome to Just Answer!
Fault code P1685 sets when the PCM doesn't receive a valid key message from the SKIM.
Did the car start and stall 3 times and now not start?
Are you using the gray head secret code key?
Can you disconnect the battery for a minute, re-connect and try to start the car and let the engine crank over for 15 seconds and read the fault codes again using the key cycle method.
I assume that is the way you got the codes before!
P1685 is still setting and there has to be a problem with the SKIM system.
Have you checked all the fuses? I am wondering if the SKIM has lost power??
This is going to be impossible to check without a scan tool. We need to check to see if we can communicate with the SKIM and if we can't, you will need a SKIM as long as the power and ground are good to it.
Unfortunately you are going to have to take your car to the dealer. The dealer is the only one that can program your SKIM secret key code. I wish I was able to help, but without a scan tool we are beat!
If there wasn't a problem with the SKIM, it shouldn't be setting that code, so I do think we are dealing with a SKIM issue here. Since you got the code to return, that is a good sign the problem is active and needs to be looked at. This could also be a problem with the PCM not seeing a SKIM message and if the PCM requires replacement you still need to get the dealer to transfer the secret key code to the PCM.
Click the following link to view and download some info about this code.
I hope this helps, let me know!
Thank you for letting me know! On the bright side it's better that than the PCM.
Thank you very much and feel free to leave feedback for my efforts!