Intermittent no crank issue
I'm having a 'no crank' problem with an 2004 PT 2.4L Auto. Pulled in to gas up. Turned key - nothing. All instrument lights were on, heard fuel pump wind up but no click or dimming of lights, nothing. Everything else seemed to work (radio, wipers, lights) it just would not start. After 30 minutes I disconnected the battery terminals, reconnected and it started numerous times as if nothing was wrong. I arrived home 30 minutes later and it wouldn't start again. The next morning it was fine again. This pattern has continued, more or less, for a few weeks.
Now (3 weeks later) it takes 2 hours and sometimes longer before it will start. The battery has been tested, the starter works, all relays are working, no security issue (according to dealer the coded key feature will shut the engine down after running for a few seconds if the key code doesn't match), all power connections to the starting circuit cleaned. There are no error codes present at the odometer or code reader.
When the system is in a no crank mode the starter relay does not 'click'. When it's in start mode the starter relay 'clicks' and everything runs as per normal. I've swapped the relay with a known good one (They all have same part number) with the same outcome. All relays 'click' when activated. Replaced cam sensor 2 months ago. There is now a full 1 second delay from when the key is turned to when the starter fires up (this seems new)
Being in the computer field this reminds me of an electrical intermittent failure due to a slight crack in a component that expands (breaks connection) when heated up. This could explain the reason for a no start when the vehicle is hot (normal) and the start when it's cool. Example: I was out this morning and the vehicle successfully started 3 separate times (within 1 hour) and each time the operating temperature was below normal and had not reached full operating temperature.
My most recent mechanic suggested replacing the PCM, I'm just not sure that is the problem and don't want to spend a fortune replacing all electrical parts.
Any ideas are appreciated!