Six two-car trains comprising one driving motor car and one driving trailer were ordered from English Electric in 1936 to work the future Johnsonville Line, which formally opened as a branch line on 2 July 1938 with the new electric trains inaugurating the service.

[6] In an editorial published in the New Zealand Herald the Minister of Railways Colin McLachlan stated that the government intended to purchase new suburban rolling stock.

[6] In addition to mechanical issues, the units heaters and doors were often faulty, leading to passenger discomfort.

The second cabs were progressively removed to provide spare parts giving increased luggage space.

[11] Ten two-car units of '46 stock were refurbished at the now closed East Town Railway Workshops in Wanganui between 1984 and 1986,[12] for continued operation on the Johnsonville Branch, where EMs did not have running rights due to their being over-gauge and having insufficient braking capacity, and for peak-hour running on the Hutt Valley and Melling lines.

In the early 2000s, the remaining members of the class underwent a moderate refurbishment to extend their operational lives to 2012.

The refurbishment largely involved a cosmetic upgrade of the exterior and interior of the cars, with new seating and a major mechanical overhaul.

[14] Due to the arrival of the Ganz-Mavag electric multiple units in the early 1980s withdrawals of the D/DM class began in November 1981 with the scrapping of set DM55 and trailer D2007 (DM 1 and D 101).

This caused issues due to delays in the introduction of further Matangi units and the voltage increase which led to a number of electrical failures on the older DM/D sets.

At the time no numbers had been given for the train sold as GWRC had nine two-car sets awaiting sale or scrap.

The set purchased was eventually revealed as motor car DM 562 and trailer D 2149, which arrived in Nelson on 21 August 2012, after being transported by road from the Wellington railway yards onto the Interislander ferry the following day.

It was announced on 23 January that the three-car DM 556 "Cyclops" set was put aside for the Wellington Heritage Multiple Unit Preservation Trust, while the two-car DM 216 "Phoenix" set was put aside for preservation by the National Railway Museum of New Zealand.

The car body was painted in Royal Blue with a white band along the side below the windows and grey roof.

The traction equipment and running gear were painted black, but were concealed under skirting until the war years when maintenance staff had them removed for ease of access.

The livery was slightly modified in 2008 by KiwiRail for safety reasons when the red outer car ends were repainted yellow for better visibility at level crossings, this modification being confined to the three heritage sets.

When it was refurbished in 2006, it was named "Cyclops" due to its single-lens headlight and repainted externally in the "Midland Red" livery with gold car numbers as per the 1950s.

The car body was repainted in olive green with a grey roof and black underfloor equipment and running gear.

The car body was painted in the standard Tranz Rail "Cato Blue" with a grey roof, yellow ends and headlight mount, and black underfloor equipment and running gear.

The car body was "Cato Blue" with a grey roof and headlight mount, yellow cab fronts and black underfloor equipment and running gear.

Car numbers were painted on the cab-mounted horn covers in dark blue descending Frutiger script, although some had different sized lettering or a serif font.