i know the PSOM is a common problem with these trucks, and my 1996 F250 7.3 gives me issues with throwing the transmission into Limp Mode when i press the Trip/Odo button and anything over 60mph the speedo goes very wonky and wont allow cruise to lock in solid.

Definitely points to my PSOM, my question is, according to the Ford TSB below replacing the PSOM with a new one will get rid of the minimal variance detection, but where do I get a NEW PSOM from? everyone talks about buying a used cluster from ebay or junkyard, but aren't i going to be in the same boat then when i put that in?

Some insight would be great! Thanks.
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TSB 96-21-11 Programmable Speedometer/Odometer Module Pointer Waver

Publication Date: OCTOBER 7, 1996

LIGHT TRUCK: 1992-1996 AEROSTAR, BRONCO, ECONOLINE, F-150-350 SERIES

ISSUE: The speedometer needle may waver and/or a light surge may occur on some vehicles when speed control is used at highway speeds between 80-113 km/h (50-70 mph). This may be due to slight dents/chips in either the exciter ring or the Vehicle Speed Sensor (VSS) and air gaps between the VSS and the exciter ring.

ACTION: Replace the Programmable Speedometer/Odometer Module (PSOM) if required. New PSOM's come with increased immunity to system variability. Refer to the following Diagnostic Procedure for details.

DIAGNOSTIC PROCEDURE
BRONCO/F-SERIES - Perform normal PSOM diagnostics per Pinpoint Tests "H" and "J" of the 1996 F-Series/Bronco Body/Chassis Service Manual, Pages 13-01-30 through 13-01-32 and Pinpoint "B" of the 1996 Powertrain/Drivetrain Service Manual, Page 10-03-11.

ECONOLINE - Perform normal PSOM diagnostics per Pinpoint Tests "H" and "J" of the 1996 Econoline Body/Chassis Service Manual, Pages 13-01-29 through 13-01-31 and Pinpoint "B" of the 1996 Powertrain/Drivetrain Service Manual, Page 10-03-9.

AEROSTAR - Perform normal PSOM diagnostics per Pinpoint Test "K" of the 1994 Aerostar Body/Chassis Service Manual, Page 13-01B-31.

Any slight dents, chips, etc., in either the exciter ring or VSS will create needle waver. Measure air gap between the VSS and exciter ring. It should be 0.38-0.51mm (0.015-0.020").

Check exciter ring runout per the same ring gear backface runout procedure of the appropriate model 1996 Powertrain/Drivetrain Service Manual, Section 05-00.

Make sure the exciter ring is mounted correctly to the ring gear. If runout is more than 0.1mm (0.004"), perform the differential runout check per the procedure in the appropriate model 1996 Powertrain/Drivetrain Service Manual, Section 05-02A or 05-02D, to find cause and repair as needed.

If all items listed above check good, replace the Instrument Cluster Assembly. Obtain the correct service part number from the Parts Catalogue and then contact the Electronic Odometer Exchange Center at (800) 259-9700 for U.S. Dealers and (800) 663-9974 for Canadian Dealers.
NOTE: DEALERSHIP MUST TELL THE ODOMETER EXCHANGE CENTER THAT YOU NEED A PSOM3 LEVEL CLUSTER FOR A SPEEDOMETER NEEDLE WAVER CONCERN.

OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage

OPERATION DESCRIPTION TIME
962111A Replace Programmable Speedometer/Odometer Module (PSOM) - F-Series, Bronco 0.6 Hr.
962111B Replace Programmable Speedometer/Odometer Module (PSOM) - Econoline 0.7 Hr.
962111C Replace Programmable Speedometer/Odometer Module (PSOM) - Aerostar 0.8 Hr.

 

70 views, yikes i hope someone knows the anwser

 

No idea where to get a new one, have you tried ford? All I remember seeing on here is used ones being used as replacements. Good luck

 

The PSOM modules are not really that high of a failure rate. Why do you think it's a problem? Have you checked the VSS sensor on the rear end punkin? Pull it out, clean it up and reinstall. Their are no longer any PSOM modules available (new) so if you purchase one online try to get one with the milage close to your current one, as they cannot be reprogrammed. If your rig has 150,000 miles on it and you purchased a used module with 350,000 miles on it that is that, nothing you can do about it.

 

Immthinking vss or wiring to vss

 

yes I have checked and replaced the pumpkin sensor, the new one is more wonky than the last, so I may put the ford one back in yet.

i think its the PSOM because I can sometimes put the transmission into limp mode by pressing the odo/trip button and I periodically have hard up shifts.

so according to the Gears magazine article, this seems likely.


as for the mileage i am not worried, i can denote it if I ever sell the truck, which I probably wont. Also mileage is fairly irrellavent with these trucks if they are over 300,000 miles or km, which mine is at 362,000, because when they hit 400,000 miles or km they automatically return to 300,000, so either way I would guess mine is incorrect.

That's according to a thread on here, and come to think of it I have never seen one of these trucks with over 400 on it.
https://www.ford-trucks.com/forums/1...r-at-400k.html

I have heard there is some other sensors that could cause the needle wobble and hard shifts, like the OSS(Output Shaft Sensor) but you don't hear near as much about them so it seems like a less common failure than the VSS(RABS) or PSOM modules/sensors.

 

If you have a blinking OD light then scan it and get the code

 

the light only comes on intermittently, does it have to be blinking in order to take it to get scanned?

 

It should store the code

 

It stores the code... did for me when I kept throwing "2nd to 3rd Shift Malfunction". I'd scan it when the OD light was both blinking and off.

 

anyone know how much the stealer ship charges to do this? or is there a cheaper place? i know my scanner does not scan those codes, and i know most of those scan for free places cant either like part source and such.

 

My dealer is on the cheaper end and they're $85/hr for diagnostics and they "claim" 2hrs for diagnostics. That's almost half the cost of AutoEnginuity... it's worth buying and having IMO.

 

wow, at that price i will go buy a couple instrument clusters from my wrecking yard and hope for the best. if they don't work, i will know its inside my tranny.

 

Find a good tranny shop to scan it. The ones around here charge around 65.00 hr.

 

If its a parts house vss it could be bad out of the box. Everytime I've seen a speedometers trans issue it has either been a bad vss, broken or frayed wire, and sometimes a tps but I don't believe that is the problem. My speedo goes nuts above 80 and it slighlty flutters from 55 on a MPH or 2 but I have a 5spd so no ill effects. I'd start by ohming out the harness and check for a dead short or loose plug.