hi everyone,my first post.
To start with:1994-f250,5.8,4x4,170,000 miles
I have the E40D trans. When the trans is cold and approx before 20 miles the trans works fine as it should,but when warmed up it starts with high rpm shifts then slambs into gears hard(all of them) and when coasting down long grade/hills with foot off accelerator I loose some gears(in neurtal) and with coaxing and slowing down it returns most of the time, then slambs into gears again.This happened last summer also,approx 8000 miles ago then cleared up till now again.
I scanned and had a code 452 with KOEO,I didn't do a KOER(do I need to do this scan for the trans problems).I replaced the vss and same trans problems.The fluid is full,little discolored,but not brown or burnt smelling and was changed approx 60,000 miles ago.There is no flashing light on the OD switch,no jumping spedo needle and no check engine light.
I was searching and reading FTE and read about checking and cleaning and applying die-elec grease to all connections,thats were I was going to start with. I would appreacate any help and guidence,I am ok with servicing and repairing,but really suck at eletronic's(getting better at it,understaning it better). Thanks in advance for your help,it seems there are many qualified people here at FTE.

 

Welcome to FTE.
452 is a CM code and not a KOEO code.
Yes a CM code of 452 will cause your transmission problems.

Continuous Memory DTC 452 indicates the PCM detected an error in the PSOM output signal during the last 40 warm-up cycles.

Possible Causes:
-- Damaged Rear Anti-Lock Brake Sensor (VSS).
-- Damaged PSOM.
-- Damaged harness circuits.
-- Damaged Powertrain Control Module (PCM).

 

I had time today to work on the truck.I removed and cleaned the connectors(vss,mlps,seloniod-behind the heat sheild,relays in fuse box and the big block connector on the fire wall) with elec cleaner and die-elec grease.I replaced the vss and cleared the 452 code from memory.Drove it and shifted smooth untill the tranny got warmed up,then started shifting hard again,got back to garage and had code #452(VSS) again.So how should I check to see if the new vss is good and I guess I need to trace the vss wires to see if they are good.Anyone have anything else I should look for.Thanks

 

On this vintage truck the speed input signal goes through the PSOM on the dash cluster before going to the computer, and since you have replaced the VSS already this should be the next thing to inspect/replace.

 

would there be a code for the PSOM,because there was a code #532(CCA-cluster control ***.),I just thought it was for the oil pressure gauge not working.Is there anything i should look for when I pull the dash apart?other tha loose connections/wires and where should I get the cluster from.Also this is my only truck, so I can't be without the truck and being tore apart.

 

532 does not sound like a valid code for your truck.
Look at the RABS module or PSOM.
If the speedometer is steady then also look at the Speed Control.

 

The code#532 was with KOER. The ABS light is not on(if that means anything).The speedometer is fine(dosnt jump,steady movement).Where is the speed control located?

 

Speed Control Amplifier:


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The 532 code is a Continuous Memory code and not a KOER code.
But if you are getting a 532 you may have a bad PCM computer.
Open it up and check the caps and see if they are leaking.

 

Is the speed control amp part of the cruise control, if so I don't have cruise control.

 

Yes it is, Ford calls it Speed Control and GM calls it cruise control.

With no ABS lamp and a steady speedometer and without speed control with the 452 code it sounds like you have either a bad PSOM with maybe loose items on its PC board (bad solder joints)
or bad wiring/plugs at the rear end or between the PSOM and the PCM computer
or maybe a bad bearing in the rear end ring gear.

But if you are getting a 532 you may have a bad PCM computer.
Open it up and check the caps and see if they are leaking.

 

is there a way to check to see if I have a "bad" new vss.The new one(vss) I installed the top where the plug go in moves 1/4" siide to side.I've been driving the truck and seems to go into limp mode sporaticly and throw code 452.Id like to check the ohms "if possible for resistince" on the vss,do anyone know what the resistence should be.I just bought a new digital multitester and if someone would like to talk me thru the process(as I said i'm learning electricial diogniosing).If the vss is good then, i need to see if there is a short/split in the wiring from the vss to the firewall block connector.thanks again

 

The VSS is a voltage/current generator and the test for the circuit is to check the voltage that it outputs.

As far as using a resistance test you could check for a complete circuit but I do not know of any ohm reading to check it. You could unplug the RABS module and the PSOM and then check at the RABS test plug under the hood for a complete circuit.







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OK,looking at the wiring diagram,I see the vss wire go to both the psom and the rabs.I thought it went straight to the psom,so I never cleaned or checked the rabs connections since I never had any codes for psom&rabs.I will check/clean& grease the rabs connections first and NAPA has a replacement vss for me.

 

I also have the oem vss,and will check voltage on that(if possible) and compare with the other one.I'm avoiding taking the dash apart until last resort?