There was only one thermocouple left at the bottom of the Pressure Vessel of Reactor 2. Now there are two, greatly enhancing the TEPCO's capability to monitor the "cold shutdown state".
Workers from TEPCO and an affiliate company (most likely Toshiba, who's in charge of probing inside the Containment Vessels of Reactors 2 and 3) finally managed to insert a replacement thermocouple through one of the penetrations on the Containment Vessel of Reactor 2 to 5 centimeters inside the wall of the Reactor Pressure Vessel (RPV).
Of the six thermocouples that monitor the temperature at the bottom of RPV, 5 of them had failed since the start of the accident.
From TEPCO's Photos and Videos (10/3/2012):
It's been a while since TEPCO last announced the details on workers - how many of them, how many teams of workers, what company they belong to, and how much radiation exposure they got from performing the task. This particular work took 2.5 hours, according to TEPCO's handout for the press (in Japanese) of the same day.