Chrysler Repair: 99 3.2 Concorde quits running/code 1684, ground clamp, cable clamp

Question
our faithful 1999 Concorde 143,000 miles has a problem. . the cruise lite comes on, and it stops running. After about a minute, a code p1684 comes up in the miles display, it goes away, a few dashes, and the word "done", then, its ok.
will start right up as if "it fixed itself"
our mechanis had it in for half a day, sid he coulnt find anythin wrong with this car. he didnt charge us a cent, but, we are still baffled as to what may cause this.

Answer
Hi Phil,
That is an interesting symptom set for a stall-out. The code 1684 means that the 12v current to the powertrain controller has been disconnected in the past 50-100 key cycles. Normally, the controller is always connected to the battery, even when the key if off. That can happen when either the actual battery connection is removed (such as either the + or - cable clamp being loose at the battery or the ground connection of the - cable wire to the frame being loose, as well off course to a purposeful disconnection). So I would check those three possibilities (looses clamps, or poor ground wire connection to the frame. In theory, it is probably the ground clamp or ground wire because the alternator would keep the current going even if the + clamp were loose.
Another possibility is that fuse N (30 amp) in the fuse box under the hood has a crack in its wire which is opening and closing when it heats up and cools. That fuse is how the powertrain is connected to the battery, via a red/white wire to pin 46 of the pcm. So check that fuse carefully, visually, or even simply replace it.
The cruise control light may be serendipitous in that the circuit that sets the cruise in action is a voltage sensing circuit and it may simply be 'seeing' the voltage disruption that is occuring as the voltage change associated with setting the cruise.
That would be my best guess.
Roland
PS Sorry for the delay in answereing. I just found your question in the 'pool' to which it had been referred. Please 'rate' my answer and where you see the question about a nomination to be 'volunteer of the month' consider a 'yes'.