Intermittent issue of transmission not shifting into gear

Tiny
ROOSEVELT FOREHAND
  • MEMBER
  • 2008 MERCEDES BENZ S550
  • V8
  • 4WD
  • AUTOMATIC
  • 152,000 MILES
My car sometimes won't go into gear and I have to cut it off then try again until it does. Why is that?
Sunday, July 18th, 2021 AT 2:30 PM

1 Reply

Tiny
SQM
  • MECHANIC
  • 6,383 POSTS
Hello,

It sounds like a fault with the transmission control module (TCM) or the ISM (intelligence servo module). Does this happen when the engine is hot or cold or both?
What error codes are you getting with this?

https://www.2carpros.com/trouble_codes/obd2

With code read it will point us to the right direction.
So first step would be to get the car scanned for codes. If it is the ISM, it does need to be programmed after install.

Let me know if you have any questions.
Thank you.

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Sunday, July 18th, 2021 AT 3:02 PM

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