I have the same problem, and I followed the advice of turning the ignition on x2 on 2002 Chrysler PT Cruiser

but no code pops up. Engine light does come on

3 answers 2 comments
scan codes with a scanner and post so we can adv
ON-OFF-ON-OFF-ON........(3X) third time leave in 'run' position and watch LED display for 'fast' codes. NOT a substitute for a good scanner and proper diagnostics though. Must cycle key through sequence within 5 seconds or so , I believe.
Thought it was twice; I'll try that.
P 1684, and P 301
Looks like 301 is Cylinder 1, and 1684 has the battery disconnected in the last 50 start-ups.
Now to find which is cylinder one. I went 215 thousand miles on the first set of plugs; 15 on these
Reqires the use of a code reader or scanner to retrive fault codes.
Thanks.