SLK 350 276 engine PO 436 code

[winter2]

Dear All

I have the engine code P0436 indicating temperature sensor 1 cat convertor cylinder bank 2 has a malfunction signal comparison faulty
All lambdas are reading correctly, when engine running, cat temps are the same. it throws the EML when starting from COLD and remains until reset.

Should i replace the probe or is it something else