I have a 2001 STS that has been giving me fits for some time. At times the car won't turn over when the key is turned, all lights and gauges work though. It will eventually start but it seems like it's happening more frequently. I cleared all codes and this is the code that set last night when it did it again TTM U1016 history. If anyone has any ideas I would greatly appreciate it.

 

my best guesses would be :

poor contact with battery cables, bad ground somewhere, or a poor/failing contact in ignition key cylinder ...

i dont believe that u1016 is related to the starting issue

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Is it possible to replace just the key cylinder or would I need to replcace the whole key ignition assembly?