Dashboard communication
 

I have had a5 speed manual, 2005 PT Cruiser convertible, no turbo or ABS, for about 2 years/15000 miles - it has run flawlessly... until recently. The first inkling of trouble was on a 1 hr drive - the car kinda 'jumped' while at highway speed. The car continued to run and I honestly thought I might have hit some road debris I hadn't noticed. I pushed in the clutch, and the revs remained high as I coasted and then they suddenly dropped. I pulled over, thought maybe it was a timing chain issue or a serpentine belt came off - and convinced myself it was the serpentine belt... it wasn't.

On my next use - my dash went dead and all the lights came on but the engine was still running. I was close to home so I turned around and parked it. I used my code reader to read that the dash lost communication (not exact wording). I reset the code and away we went. I used it for a few short runs and it seemed fine, so I used it for a long run in the city. The same issue - the dashboard would die, and if I continued to drive with a 'dead' dash, eventually the engine would stop running. It always restarted - albeit, once in a while, I would have to wait a few minutes - otherwise it would just crank without firing. I know this because I was 20+ miles from home and this 'dying and restarting' was happening almost every 3 blocks (it was a LOOOONG ride home).

I got home and:
1) pulled the battery positive cable
- removed all corrosion from the cable connector
- sanded all the surfaces inside the connector and the battery post
- using good old (forbidden) acid plumbing flux - soldered all the terminals on the stock battery cable
- reassembled all connections using dielectric grease (VERY thin coat)
2) repeated the procedure on the negative cable
- removed the chassis ground and engine ground; cleaned both and reassembled with dielectric grease

Took the car out - no more dying, but I did get the dashboard communication error. A couple more YouTube's later - I took off the steering column covers and pulled the connector off of the back of the ignition switch. I could not comfortably get anything into the wire connector to 'clean' the surface (knock off any corrosion) inside the wire connector or on the larger spade connectors on the back of the ignition switch. I replaced the connector, again with a small mount of dielectric grease.

Did a 5 mile testdrive with no issues. I drove the thing for another 30 miles flawlessly. I thought 'Great - job done'... but today - the dash died again and then the engine stalled shortly after. This time, the code reader was showing an O2 sensor error (again - I don't have the specifics) and the interesting part was that the dash didn't 'die to zero' - the speed indicator went from 50 to 20 and the RPM indicator went from 2500 to 500 and then the engine eventually died. The indicators went down - not the speed or engine RPM.

Any suggestions? I'm GUESSING that the connector on the back of the ignition switch is once again failing (only 33-35 miles since I did the 'fix' - so maybe not?). There are a couple frame grounds where the wiring harness attaches under the hood - I haven't touched those. I don't have the sophisticated diagnostic tools I've seen online with one trouble-shooter (a 'scope' watching the PCI connections... a 'breakout box' of some sort to evaluate signaling). I've read about others replacing their PCM... about losing power to plugged catalytic converts... about bad grounding in the harness. I'm inclined to think it's the latter of the 3 - but looking for some experience to point me a little more specifically if possible.

Thanks in advance!! Arden