Work continued on 89001 at the UK Rail Leasing works at Loughborough. Testing of all the new systems took place in late 2023 and into 2024, but problems were found with air leaks in the Davies & Metcalfe E70 brake frame. After a delay due to obtaining the correct O-rings, this was finally corrected in Spring 2024.
With all the new and original equipment finally installed, a start could then be made on the system testing. This involved detailed step-by-step checks of all the new systems to make sure they were working correctly, and also a full re-test of the other loco systems. This work was completed in June 2024.
On 3 July 2024, 89001 was powered up on a live 25 kV supply in one of the test bays at Loughborough for auxiliary systems checks, then short distance movement tests were carried out on the test track. This was the first time that the locomotive had run under its own power on all six traction motors for around 25 years.
15 August 2024 saw Locomotive Services Ltd's class 37 D6817 (37521) haul 89001 from Loughborough via Leicester, Nuneaton and Stafford to the Locomotive Services Group's depot at Crewe. Further testing of 89001 will now be carried out to meet the requirements for running on the main line network under its own power.