[8][9] Tiemann made regular appearances in the Nürburgring Endurance Series during his career, taking 19 overall victories in total.

[10] In 2000, Tiemann joined the Deutsche Tourenwagen Masters series with Team Persson driving a Mercedes CLK in Original-Teile livery.

However, during the race at Imola on May 23, Tiemann collided with another car at the rolling start and was forced into a retaining wall at high speed.

He sustained brain trauma, a fractured vertebra and broken ribs in the impact, and was placed in a medically induced coma to assist his recovery.

[17] He was moved to Germany, and later regained consciousness and mostly recovered, but has been unable to race due to the resulting neurological damage and other problems from the accident.

Following retirement from racing, he became a brand ambassador for Mercedes-Benz and also runs a construction company building nursing homes in Germany.