And this fault will lead to some services in West Yorkshire later this month being disrupted.
Twenty-four trains from Northern's new electric (Class 331) and diesel (Class 195) fleets were recently withdrawn after being found to have a problem with a shock absorber designed to prevent swaying in the carriages.
The fault is not related to the issue currently affecting LNER, Transpennine and Hull Trains' Hitachi Class 800 units, which were all withdrawn from service on Saturday pending safety checks.
And on Friday a meeting of West Yorkshire Combined Authority’s Transport Committee will hear that modifications required to deal with the fault are likely to take “several months.”
This will lead to disruptions when the new timetable in introduced next week.
In 2019 Northern announced a £500million investment in new trains, which the company said would “mark a step-change for rail travel in the north of England.”
The fleet of 101 trains were built by Spanish company CAF and have been brought into service over the past two years.
The new models have replaced Pacers that were found on many routes on the network.
The 100th train was unveiled shortly before Christmas.
But a report to the Transport Committee will hear that the fault in the models has proved an “area of concern” for Northern.
Members will be told that the new timetable, being rolled out on Sunday May 16, will be affected by the decision to remove trains from service - with replacement bus services likely on one route.
The report to the committee says 30 trains have been removed, although Northern told the Local Democracy Reporting Service this figure is actually 24.
It says: “One area of concern for Northern regarding their new electric (Class 331) and diesel fleet (Class 195) is a fault which has been discovered in a yaw damper bracket.
“A yaw damper is a large shock absorber which connects the wheels to the train body.
“The fleet have been inspected and 30 trains have been temporarily withdrawn from service and a modification has been developed which is expected to take several months to fit, a specific timescale will be made available shortly.
“No faults have been found in the remainder of the fleet, but this will be investigated further.
“Northern have advised that the removal of the 30 trains will not adversely affect the current timetable because of its reduced nature but for the May timetable there will be a bus replacement for the through services Huddersfield - Wakefield - Castleford.
“Also, additional peak services from Knaresborough - Leeds will not operate but Northern have advised that it is considered the remaining peak provision will accommodate the suppressed passenger demand so bus replacement will not be required.
“This reduction of the services in the May timetable is expected to last for a short period only. The existing fleet will need to cover for the removed trains so potentially there is an enhanced risk of overstretching the remaining fleet or trains running with less than planned carriages, this will be monitored.
“Transpennine Express have also carried out precautionary checks on their Nova 2 trains that operate on the West Coast Main Line as they were built by the same manufacturer. Fortunately, those checks were completed, and no faults were found.”
A spokesperson for Northern said: “A fault has been identified on some of the new fleet of trains built by CAF and operated by Northern.
“The fault is affecting the brackets attached to yaw dampers ,a system designed to reduce swaying motion in the carriage, and has resulted in 24 trains being removed from service while the issue is investigated.
“The remaining 78 trains in Northern’s CAF fleet have been fully checked and are operating as normal. The units still in passenger service will be regularly checked as part of the ongoing engineering process.
“While the root cause of the problem has not yet been fully established, we continue to work closely with CAF to resolve the issue. As part of this work CAF and Northern have developed an interim modification which, once fully tested, will enable the entire fleet to return to customer service.
“Work is ongoing to design a permanent modification that can be applied to all CAF trains operated by Northern.”