Where is PSOM?!

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Aug 20, 2005 | 06:24 PM

elvis on cape

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Where is PSOM?!

'93 F250 5.8L 2WD

Could anyone shed some light on my PSOM problem? I'd be very thankful for any help. My speedo and Odo are dead and the truck is running poorly, and some advice has been given about the PSOM. Where in the truck can I find it, and is it something I can replace and then calibrate myself? Thanks for any help you can give.

Elvis

Aug 20, 2005 | 06:46 PM

Franklin2

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From: Virginia

I got this off an internet search. It seems the PSOM is the speedo unit itself, or it's made into the speedo unit.

Quote:

This vehicle is equipped with a programmable speedometer/odometer module (PSOM), an electronic unit made to look like a conventional speedometer. This unit receives an AC signal from the DSS and drives the speedometer needle to indicate speed. It also converts this signal into a digital signal to pass on to the PCM and cruise control servo (if equipped). Since the DSS signal feeds the ABS module and the PSOM ... there was no ABS problem or light ... and the speedometer read correctly, its signal would be OK. The fault would be in the PSOM's ability to read and generate the appropriate signal to pass on.

This brings up a good point. If the VSS(vehicle speed sensor, he calls it a DSS) is not working, you would get an ABS light. So you must be on the right track thinking it may be the speedo unit. Does the cruise control work?

Aug 20, 2005 | 08:59 PM

elvis on cape

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Nope, no cruise control. The speeedo and odo are just dead. I didn't want to have to start taking apart the dash, but I guess maybe I will. Thanks for responding.

Elvis

Aug 26, 2005 | 01:28 PM

subford

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From: Easton,Ks

Sounds like you have a bad VSS sensor or wiring, the VSS sensor is on the top of your Rear End Differential Housing.

Jan 9, 2006 | 11:12 PM

caddy_85_02

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I have the same problem

I bought a 94 full size bronco and it has the same problem (no speed odmeter or odmeter) so i put in a new vss yesterday and still nothing what would cause this?

Jan 10, 2006 | 06:45 AM

subford

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From: Easton,Ks

Quote:

Originally Posted by caddy_85_02

I bought a 94 full size bronco and it has the same problem (no speed odmeter or odmeter) so i put in a new vss yesterday and still nothing what would cause this?

Check Fuses # 8 (15A Hot at all times) & 18 (10A Hot in run), both in the passenger compartment fuse box.
If the RABS light is on you may have a bad (bent) tone ring or wiring from the VSS to the RABS Module.
If the RABS light is not on the PSOM may be bad, this is assuming that fuses 15, 13 & 17 and the light bulb are OK.

Last edited by subford; Jan 10, 2006 at 06:49 AM.