The trains in the Northern fleet that are undergoing refurbishment works, as per the franchise agreement are:

• Sprinters: Class 150/1 & 150/2
• Super Sprinters: Class 155 & 156
• Express Sprinters: Class 158/0 & 158/9
• Turbostars: Class 170/4
• Class 319, 323 & 333 EMUs

Improved Passenger Facilities

The refurbishment programme will make the trains more comfortable and provide them with new facilities such as wifi, one USB charging port for every two seats, and real-time passenger information. All the carriages will get energy-efficient LED lighting. Of course, the trains will also undergo thorough cleaning.

Accessibility

One of the reasons Northern is replacing its entire Pacer train fleet is because they will not meet accessibility requirements come January 2020. Consequently, Northern is also investing in making its refurbished fleet fully accessible. For example, Northern is fitting them with accessible toilets and baby changing facilities.

Train Performance

A third aspect of the refurbishment works focuses on improving the trains’ performance and maintenance. In essence, Northern is using digital solutions to help keep more of its fleets on the rails and reducing downtime.
source= https://railway-news.com/northern-refurbishment-two-thirds-complete/