EMD built 13 GP40P's for CNJ in October 1968. On longer frames than the standard GP40 to accomodate a steam generator, the GP40P's produced the same 3,000hp from the EMD 645E3 16-cylinder prime mover. CNJ assigned the GP40P's number series 3671-3683.
Originally paid for by NJDOT, CNJ used the GP40P's for passenger service to the Raritan Valley Line and the North Jersey Coast Line. In April, 1976, Conrail continued to use the GP40P's in commuter service under contract to NJDOT until 1979, when NJ Transit was created. Conrail continued operating the GP40P's under contract to NJ Transit until the end of 1982.
CNJ colors remained, with only an NJDOT renumbering, until the fall of 1978 when NJDOT's dark blue, gray and red stripe was commonly seen on both the GP40P's and the E-8A's. In the last years of CR's contract with NJ Transit of mid-1981 through 1982, white and silver paint schemes of NJ Transit replaced the NJDOT dark blue.