Well hello friends...
I'm battling the notorious 452 code (no VSS input) and a dead speedometer, causing my E40D's hard shifting, blah blah blah...You've all heard this story.

I pulled the code (452) and started trouble shooting by the process of elimination. I replaced the VSS thinking that was the cheapest and easiest fix. Nope, wasn't it. I went on to the PSOM, that seemed a common problem. I swapped it with another from the pick n pull... No relief. Now, I am stuck. What next? should I take it in for a diagnostic, or will they likely pull the code and tell me what I already know: "the speedometer isn't getting a signal from the VSS... Now give me my monies" Is it really likely to be the tone ring?

Unfortunately, I have zero experience with electrical diagnostics. I am also extremely limited in my tools and shop space available, like a floor jack and jack stands to lift the rear-end and test the vss circuit output.

can someone explain what to test for next, and more importantly, how to test, please?

 

Ouch. Don't throw parts at it... find what's actually causing the problem, replace what's broke and save your money.

First of all, check all your fuses. Don't just eyeball them, use a test light if possible. Ground the test light somewhere to the cab, then with they key on touch the light to each one of the exposed metal terminals on top of each fuse.

No light either side=no power to circuit.
Light only on one side of fuse=blown fuse
Light on both sides of fuse=good fuse

If you don't understand this then let me know and I'll explain better.