2004 Cadillac CTS CHECK ENGINE IGHT

Last tank I went to fuel low before fill up. Normally I keep above half tank always. Just before the low fuel signal came up - in city driving - check gas cap came up - gas cap is on - tight and all the turned beyond three clicks - CEL came on and staying on - last six days - I am only driving city about 12 mile each way most ly 25, 35, 45 mile roads taking about 30 minutes each trip - no highway trip in the last 6 days - the CEL is on - occasionally check gas cap is coming on -performance and running is same as before - I was told - it would need 40 or more drive cyles to reset - though the manual says "few trips" - short of going through the expenses at the dealership for diagnostic code read - etc. Etc. Then just do code buffer clear and reset which mayrun $100+ to $300+
-is there work around simple layman fix? Thank you. SSikdar