ML Transmission problem

[Steviemboy]

Hi all, I have a transmission problem, my ML W163 270cdi with 269,000kms won't tiptronic however it will kick down and rev passed 3500 rpms only when cold. Once hot it will not kickdown or rev passed 2500 rpms. the tiptronic does not work either when cold or hot.
I had oil in the adapter 13 pin plug so replaced the part into transmission and had faults cleared with P1912-002 ESM but has failed to clear under Star.
Question is if I replace gear selector shifter will this solve my problem or is there something else I need to look at... if you can gude me to a past post Any help much appreicated ....cheers Steve
I should have added there was not dash warnng lights on and the transmission oil level was OK.