In 2009, when the use of the class 420 at the S-Bahn Rhein-Ruhr was completed, the Essen depot delivered several ET 420 of the fifth and sixth series to Frankfurt. Although the Frankfurt plant made great efforts to align the railcars to the Frankfurt units (for example, most railcars were still redesigned in 2007), they were in such poor condition by the end of years of poor maintenance in North Rhine-Westphalia that From then on, they were usually taken out of service directly at the end of the investigation period.
