A large amount of preparation works were undertaken in the Wellington region to allow the units to operate: clearances in tunnels, at platforms and under some bridges had to be increased to take the new trains. KiwiRail installed eleven new rectifier substations to increase the electrical supply for the new trains (nine on existing electrified lines, and two on the new extension to Waikanae), and hardened the signalling system against interference from their AC traction equipment. The operating voltage was increased to 1600 volts DC to maximise the power available, with the overhead supply being 1700 volts DC. Despite the power upgrades the length of Matangi trains was initially limited to a maximum of six cars out of concern for the load long trains would have on the power supply. Testing performed by Tranz Metro and KiwiRail in September 2011 with eight-car sets in revenue service on the Hutt Valley and Kapiti Lines found that the network is able to cope with a limited number of long trains (one at a time on the Hutt Valley line and two on the Kapiti line) resulting in eight-car trains being permitted. The first unit, 4103, operated preview services on 23 December 2010: the 9:05am Hutt Valley service ex-Wellington and the return 10:00am service from Upper Hutt. After these services it returned to testing duties, including four-car running with 4132. It was intended for the units to be running in regular service on the Hutt Valley and Melling Lines from January 2011, followed by the Johnsonville Line by May 2011 and Kapiti Line from July 2011. but this has been delayed. Regular revenue service commenced on 25 March 2011 with unit 4103 running on the Hutt Valley Line, initially running two off-peak return services to Upper Hutt and a Melling Line service each weekday However a combination of slower-than-expected testing, certification and driver-training programmes saw this timetable slip, prompting criticism from commuters. Overcrowding on existing services saw temporary measures introduced in April 2011, with morning peak Melling line trains replaced by buses to free up units for the Kapiti and Hutt Valley Lines, and the minimum fare removed on Wellington-bound Wairarapa Connection services to allow Hutt Valley Line passengers to use the train without penalty (the latter change became permanent in October 2011). on the
Johnsonville Line. The Matangi units were the first new rolling stock to serve the Johnsonville line in 74 years. Other units were introduced to service as they arrived and completed testing and services checks and were cleared by the New Zealand Transport Agency. In June 2011, all seven units in service were temporarily withdrawn after problems was discovered in the auxiliary power units of two units. A faulty inductor coil in the APUs caused them to overheat, and the trains were fitted with extra cooling fans and settings for the APU power supply were altered so the trains could continue in service while replacement APUs were shipped out from Korea. Introduction to the Kapiti Line was achieved in August 2011 when sufficient units became available. Another significant milestone was achieved in November 2011 when the units took over about 50% of the weekday off-peak services on these lines from the Ganz-Mavag units. Services began on the Johnsonville Line on 19 March 2012, having been delayed by a combination of driver training needs, units being required on the other lines due to rolling stock shortages caused by reliability issues with some Ganz units, and the withdrawal of the
EO/SE set from service – ironically the older DM/D class units used on the Johnsonville line had fewer issues - and operational clearance not being granted by NZTA. While all units are capable of operating on this line, a small number will initially be dedicated to operating the majority of services.
Rail squeal Not long after the units were introduced on the Johnsonville Line, residents along the line started complaining of the trains emitting a high-pitched squealing noise as they rounded some corners. Although squealing caused by wheel slip is not uncommon on rail systems worldwide, the gradient and curve radius on the Johnsonville Line exacerbated it. During the 2012-13 Christmas/New Year period, dispensers of friction modification fluid (oil) were fitted to the line to lubricate the rail and help reduce the noise. The fluid has produced mixed results, reducing the squeal in some places but making no difference on others, however has the unfortunate side-effect of reducing rail adhesion – when combined with a wet rail, it has caused trains to overshoot platforms and to lose traction, resulting in cancellations or delays. Wheel dampers are also to be trialled on two units to help reduce the squeal. The 5000 series units, introduced from mid-2015, have sound dampeners in-built. A rubber ring is placed inside the wheel to reduce resonance as the wheel turns through a curve.
Parts supply In 2025 a parts supplier for Matangi trains
Trovon Australia which was owned by a Malaysian company went into administration and in January 2026 was liquidated in Australia. It supplied parts for HVAC a/c units, air compressors and brake units through a New Zealand branch in Upper Hutt. In January 2026 seven Matangis were waiting parts, and Hyundi Rotem and KiwiRail were expecting a further four units to be awaiting parts before more parts were available in August 2026. However this was not expected to result in a shortage of Matangis for existing services. == Accidents ==