Gents -
Long story short, my full size 95 Bronco (E4OD) has an intermittent shift lock up issue, that "may" be caused by an open speed sensor circuit.


Intermittent hard shifts, no lock up, & flashing OD indicator LED on shifter. Sometimes shifts great...


Mech tells me there is a bad control module on the instrument cluster, that the circuit routes through - enroute to the ECM. Make any sense?


At any rate, the word is that an instrument cluster is needed, but Ford says "discontinued", & no one seems to have a source for OEM, or re-built...


So anyone have any thought on either the diagnosis - or parts availability issue?


Thanks in advance!

 

Your mechanic is referring to the PSOM(speedometer). If the speedo shows good speed with not wiggle of the needle, the VSS(sensor in rear axle) is OK. Most likely the PSOM is not sending out a good 8000 pulse per mile speed info to the ECU.

As the OD light is flashing, pull the codes.

Here's a thread of exact issues you have: https://www.ford-trucks.com/forums/1...off-light.html

 

Thanks for the link, & info:


"The code 452( insufficient input from VSS)means alot. The PSOM sends out the 8000 pulse per mile to the ECU(which controls the E4OD tranny) and speed control. That is a square wave about 12DC. If the ECU does not see a good square waveform it will give the code 425.

The PSOMS I fixed were due to leaking capacitor that ate up the output circuit of the PSOM's 8000 pulse per mile output. What this means, the speedo and odo will operate properly but PSOM will not send out the correct speed info giving you the flashing OD and hard shifts, also the speed control will not operate correctly as it will not hold speed."


The tranny shop has already thrown in the towel, & referred me to another local shop, that specializes in auto electric.


Speedo & tach readings seem OK, but hard shift - and / or failure to go into solid lockup.


Shows Code #452 - Open vehicle speed sensor circuit. The VSS has been replaced - w/ no effect...


Guys at the shop are telling me the entire instrument cluster needs to be replaced. If that were to fix the shifting issue, I'd be a happy camper. Problem is they can't seem to find the parts - either OEM, or rebuilt.


No local interest in board level repair. Is the PSOM an integral part of the speedo, or separate?

Any thoughts on a parts supply source?

 

The entire cluster does not need to be replaced. The PSOM is removable from the back side of the speedometer/odometer assembly. But it would behoove you to verify the wiring from the PSOM to the computer (PCM) is good. The only place you will find a PSOM is probably a salvage yard.

Some photos from Subford: https://www.ford-trucks.com/forums/1...l#post16552466


A good diagram of the VSS signal flow and other components.

 

There's a cheap sensor on the rear end can't remember the name it looks like an ABS on the inside above the ring and pinion I was experiencing a lot of different issues as a lot of people on this site I change that sensor very cheap and my trans issues shift issues and overdrive light blinking all went away after I rewired the corroded trans harness that connected to the driver side trans which they have a harness extension they sell for a fix so it obviously was a problem for them to make a fix for it . hope this helps