The automatic transmission control unit for the Nissan X-Trail T30 has the following part number:
RE4F02A
This is a four-speed torque converter automatic transmission that was used in the Nissan X-Trail T30 from 2001 to 2007.
The location of the automatic transmission control unit may vary depending on the specific year of manufacture and vehicle configuration. It is usually located either in the engine compartment or under the center console.