PSOM

[turbo elk]

Do the IDI diesel trucks (1991) have a PSOM module on/in the instrument cluster? Or is they only on the digital dashes?

 

[crash-harris]

'91 would be a cable driven speedo. VSS is in the transmission tailhousing if 2wd, in the t-case if 4x4.

 

[turbo elk]

How often does the VSS go out and what would the symptoms be?

 

[crash-harris]

ABS light (malfunction), cruise control not working for the electrical part.

Speedometer/odometer not working for the mechanical aspect.

What problems are you having?

 

[turbo elk]

Torque converter not locking up...Transmission place told me my map sensor was bad, I got one at a part's store and guy behind the counter told me it could be the PSOM like his.
My next days off I'm going to check/replace my TPS and check voltages at the tranny plug on pass side.

 

[crash-harris]

...guy behind the counter told me it could be the PSOM like his.

Remember, he's got a '91. There is no PSOM. That started in '92. Although, if you have an auto tranny, transmission operation issues could be a result, but I still don't remember if the transmission controller uses the pulses generated by the cable/gear driven VSS.

I've never owned a slushbox ;p

 

[OLDBULL8]

Torque converter not locking up...Transmission place told me my map sensor was bad, I got one at a part's store and guy behind the counter told me it could be the PSOM like his.
My next days off I'm going to check/replace my TPS and check voltages at the tranny plug on pass side.

Take the Map sensor back and get a refund, you have on such thing on an IDI. You do not have a PSOM, you have an EEC-IV also known as a TCM (Transmission Control Module).
Answer these questions first before you do anything else.
Is the OD light blinking on the shift lever?
Is the OD light ON just dim?
Is your Tach working?
Is your Speedometer working?
Do you have only 2nd and reverse?
Do you have all the gears except lockup, not shifting into OD?
Have you checked the fuses?


Do NOT drive it until fixed. It's possible to do damage to the trans.

 

[turbo elk]

Everything works as it should, just no TC lockup.
The map sensor is on the passenger side fire wall, a couple wires and what looks like a vacuum nipple that doesn't go anywhere.
The guy at the part store just had a thought about the PSOM.

 

[crash-harris]

That's where mine is too...on my 300 inline six. Not sure how you have a diesel with a MAP sensor. The MAP sensor is part of the speed density system on EEC-IV equipped F-Series trucks (87-91) and determines fuel injection by sending the EEC-IV a frequency signal, not a voltage signal. No association with the transmission (same between gassers with maunal/auto transmissions).

 

[turbo elk]

Crash, that's exactly what I thought when they told me that it was bad (MAP/MAF).... Auto zone told me there wasn't on the on the truck,a different part store said they had one in stock, took the part home and found the thing on the truck.

 

[crash-harris]

Hmm, doesn't seem right. Anyone else here have one?

 

[79jasper]

Is the hose coming off it hooked to the intake?

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[crash-harris]

Since the MAP sensor requires vacuum, I'd imagine that it's connected to the vacuum "manifold" (small plastic splitter fitting on the firewall).

 

[79jasper]

Yeah but it reads varying vacuum/boost.
Apples to oranges, but the psd/e40d uses it for the trans. Hooks right to the intake plenum.

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[crash-harris]

Hmm, I'll chaulk it up to my ignorance of auto transmissions

Though it seems strange that no other IDI owners here have mentioned having one. Guess someone could have done some swapping hoodoo.