360 F1 not engaging

Hi everyone, I am new to this forum. I purchased a 2003 360 spider about a year ago. It has been running great until last weekend. I was driving normally coming to a stop, it was downshifting by itself and appeared to be downshifting slower than unusual. It went down into third and then directly into neutral. After that, it would not shift out of neutral. No errors or anything. I had the car towed home and connected my launch scanner to it. I manually selected a gear and when I selected 3rd the transmission came back to life. I next ran the gear actuator calibration procedure and it stopped midway and I received two error codes P1741 (Engagement Potentiometer absent) and P1742 (Selection Potentiometer Absent). Is it possible that both of these all of a sudden are not working properly, or is it something else? Also, I looked online and both of these are very expensive (over $1K each), has anyone replaced these with the Peugeot Throttle Position Sensor 9642473280 which costs about $30?

I drove the car yesterday and it rode fine, but it did beep at me once and did not shift, but did shift after I pulled the lever again. Some more information, the clutch is almost new at 78%, no slippage at all. The PIS is set at 4.83.

Any help would be appreciated!!!

 

Thanks for the replay, I will try this and report back

 

Thanks for all the replies. Just to clarify, when it failed to change gears nothing worked. Somehow it appears that the car thought it was in 3rd gear, when it put itself into neutral. When it fixed itself, it was working fine through all of the gears. I took it out for a drive again yesterday and it worked fine. I plotted the f1 system pressure and it remained between 40 and 50 psi. I will try to post the graph. I did take the undertray off and one of the sensors appears to have some oil on it. Could this be the problem? I would not tell where the oil was coming from, but it appeared to be gear oil.

 

Thanks for the information on your 355. The battery on the car is new (6 months old AGM) shows 13.2 v on the charger and over 14V when the car is running, so I do not believe that it is the battery.