Lefty,
Far to many, be it at a dealership or on forums act as you say. The dealership pay structure rewards replacing parts and not diagnoses.
What I am trying to point out is the correct way to attack the problem based on what we "know" at present. The present symptoms, do not present in a way that makes the shifter look probable. So far it functioned by shifting the car out of park. That doesn't rule it completely out, but moves it down the probability list a fair way.
With no trouble codes to go on, I hesitate to point to one part or another. I will say the symptoms are CONSISTANT with an interlock code, but not what underlying problems are causing the interlock. There just isn't the info available to us to make any one part the cause. There are a few trouble codes that do cause in interlock, so that does narrow it down a bit. Truth told I haven't absorbed the service manual enough to say with any certainty what all those codes are that will trip an interlock.
Once the underlying code is known, if it is an interlock problem, that doesn't tell what is wrong, it tells you where to look.
If I had this in front of me, I would read the codes and record them, then clear the codes and see what happened. If the car went into drive and rev I would drive it around to see if I could reproduce the problem. If the code came back before I could drive it, that is a good indication it is a valid code and my attention would be on what that code is for.
If it takes some drive time, or say sitting overnight for the code to come back, these are things that are not paid for in the typical repair establishment, so they don't get done.
It is also possible that you could clear the code and it will not come back in any reasonable time frame to diagnose, and that can be very hard to sort out. I had one car that would set the same code once every 3 weeks to a month. That can be very hard to sort out, because you can't test with any accuracy and unless you had a scanner plugged in and someone watching it all the time, there is little to tell you what the cause of the trip was.
Some people have the mistaken idea that the dealership personnel know the car the best. While they are most likely to get the factory training, and have all the nice factory tools, an independent shop that specializes on EV's might have a better feel for an EV problem. There can be a real sharp dealership mechanic, but that is not a given. Many who are really good, move out on their own or to an Independent shop that can and does reward their ability better than the dealership pay structure can.
I've worked in all environments, and if pressed to say, I would say the independent shop, is willing to put more man-hours into to solving the problem, but also often lack the latest factory training and tools. A dealership is more likely to slap on a part and shove it out the door. Both can get lucky and both can fail.
Guessing often does not work, but I will admit, like the problem that only shows itself once a month or less often, that guessing as about all you have. I try not to guess, but follow the logic and eliminate things as being the problem through testing, until the root problem is found. To do that you must have some understanding on how thing act and interact, so the results of tests and symptoms can point you to the cause.
Early on I said I had an idea, but would not guess. That remains, I think the symptom is caused by an interlock, but without anything to go on to say what caused the interlock, it would be counter-productive to send someone chasing off in the wrong direction based on a guess. I could very well be wrong about the interlock, but so far that is what fits the symptoms best. Until we have codes and can confirm them as valid code, and not erroneous codes set by mistake, via clearing and seeing if they come back. Any guess to the root cause wouldn't be helpful.
In the last few weeks we have had at least 4 "no start-no move " complaints, that many have advised replacing the 12 volt battery to solve, this is one of those threads. Out of the 4, 3 have proved without a doubt the problem is elsewhere and the one that did appear to have a low battery, the battery passed 2 load tests after being charged and had enough "reserve capacity" for a 3 hr load test. SO anyway you look at it that is at least a 75% failure rate on the arm chair guess, and may be higher, the last may still have a charging issue, not a battery issue. In two the owners spent money on a battery they didn't need, and were right back where they started after spending that money.
By all means I want people to try and help, I am trying to help. I just want to stress proper diagnosing before recommending replacing parts that haven't proved (yet) to be the problem.
Having your car break down is not a pleasant experience, and can be a costly one even if only the offending item has to be replaced, it is much worse when you have to throw money on stuff that ends up not fixing the problem.
Peace!
Also, make note of the battery voltage with only a 24 watt load which is me with just the dash on, no accessories like fans lights, heaters, etc. I suspect the 12V battery, but I'm going to check first if it really has an isolation issue with the case. If I find no issues, then I'm going to suspect the 12V battery. I'll start another topic just for this so as not to clog up this one so much.
