W164 ML320 ISM (A80) Stuck in Part / Recallibration

[DaveyLC]

My misses phoned me up on a panic on Friday when the ML got stuck in Park at a petrol station; the dash was saying 'Transmission not in position P' yet the box was definitely in park so recovery would be a nightmare.

I borrowed my father-in-laws STAR system and used that to remove the stored codes and force the ISM into drive which got the car home but as soon as you remove the key it goes back into park and it gets confused again.

I limped it to the father in laws workshop the next day to remove the ISM and get the details from it so I could order a replacement.

When I refitted it I decided to go through the replacement and Recallibration process which involved:

preparing the unit for transport
'removing' and fitting the 'new one' (obviously I just left the old one on)
Then finally recalibration for which the unit goes mental selling between P-N-D-R

After that miraculously it was good as gold and is working perfectly!???

So the question is was it just confused or should I really think about replacing it?

I also noticed a 'Charge Spring Accumulator' option but it kept failing, does anyone know what this is?


Thanks for any help / advice!

 

[DaveyLC]

I take it no one else has had experience of this?

 

[BlackC55]

I would be replacing it. I have done about 5 now and its not fun when it sticks in P.

 

[DaveyLC]

Thanks for the reply, have you ever re-calibrated one that had played up?

 

[BlackC55]

Thanks for the reply, have you ever re-calibrated one that had played up?

Yes. It doesn't last.