Although the designation suggests a passenger locomotive, the P 4 was an express locomotive built by Maffei for the Palatine Railway in 1905 and 1906. It was based on the Bavarian S 2/5, but had a larger grate that was situated completely behind the rear driving axle. Because of this, the wheelbase between the rear driving axle and the trailing axle was made longer and the trailing axle needed a radially adjustable bearing. The driver diameter of 2,010 mm or 6 ft 7 in ensured a low rotational speed when running fast.

It also had a conical smokebox door and additionally a wind cutter cab. From the start it had a Pielock superheater, but due to problems with corrosion this was later removed. In the preliminary Reichsbahn numbering scheme, all were still in service and received the numbers 14 151 to 14 161. But before the numbers could actually be painted onto the locomotives, all were retired.