1995 Ford F-250 4X4 PSOM Repair

This video outlines the process used to repair the Programmable Speedometer Odometer Module (PSOM) for many of the 90’s Ford vehicles. The PSOM is vital to transmission shift quality since the Vehicle Speed Sensor (VSS) output passes through this module on its way to the Power Train Control Module (PCM).

When there is an issue with the VSS circuit, a code 452 will generally be stored in memory however there will be no check engine light. Instead, the “O/D” light on the shift lever will flash constantly about twice a second. Along with this, transmission shift points will be raised along with line pressure creating a very hard and abrupt shift since at this point, the transmission is in limp home mode. Continuous use in this state will shorten the life of the transmission.

This video doesn’t cover all repair scenarios one could encounter with the PSOM, only the particular failure that I’ve experienced. In some cases, the failure may not be obvious thereby requiring you to obtain a new PSOM from the dealer and having the mileage programmed in. However, that part is far cheaper than a transmission rebuild. So if your transmission is going into limp home mode, the PSOM is often one overlooked item to examine prior to dumping allot of money into a complete transmission rebuild. (1/1/2015)