Ford PSOM Instrument Cluster 1992-1996 Troubleshooting

Transmission shifts hard | Speedometer and Odometer not working 

The VSS is known to fail especially since this is an aging vehicle you must inspect and replace the (vehicle speed sensor) with an OEM MotorCraft one. 

Below you'll see an illustration of how the PSOM (instrument cluster) along with the VSS (vehicle speed sensor) work together and what other modules come into play. 

When one of the systems that work together fails or is intermittent, your vehicle might experience hard shifts, the speedometer doesn't work, or both. It's quite unusual that the shifting gets affected by a faulty VSS or PSOM however it's very much possible with these specific vehicles. That's not to say a hard shift couldn't be caused by something else. 

The VSS signal goes to the RABS (Rear Analog Braking System) control module before it continues going to the PSOM (instrument Cluster), The output of that goes to the computer PCM (Powertrain Control Module) and Speed Control module.

It's a process of elimination when it comes to the transmission hard shift and/or speedometer not working correctly. Try unplugging the Speed Control module for a while, and see if the hard shifts go away. If not, plug it back in then do the same with the RABS module (located behind the glove box).

The PSOM (Instrument Cluster) is commonly known to fail and you can have peace of mind knowing that when this comes in for repair, we address the circuit issues that may cause these issues to occur. If your vehicle is still experiencing the same symptoms, refer to this guide to check other parts of the system.