Cruise control diagnostics don't work

(Cross-posted to both AAF and AMFE usenet groups)
The CC on my '98 Expy (V8, AWD, Limited) failed after almost 100K of faithful service. Followed the self-test procedure in the workshop manual
and didn't get very far. Not even trouble codes being flashed. Checked wiring, fuses, clock spring contacts; all fine. Well, it's a bad servo, I thought. So bad that it can't even diagnose itself. After being cruise-less for a couple months, I purchased a new one. Installed it, pushed the buttons in the specified sequence, you guessed it: the same result as with the old one. Well, there was one significant difference -- took the vehicle for a spin, and the with the new servo the CC is working just fine.
Perhaps I am doing something wrong, but it seems that the test procedure for the fancier body style, the one with the tiny cruise control buttons on one side of the steering wheel and radio/climate control buttons on the other might be different. Anyone aware of tech note or something to this effect? It will probably apply also to the fancier Crown Vic/Grand Marquis and others of similar vintage. Would be nice to have it if the thing ever fails again. And it may prevent others from throwing away a good CC servo (which ain't cheap) when the problem is actually elsewhere.
For completeness, the procedure in the book goes something like: 1) Hold the OFF button while turning ignition to RUN. Release the OFF button 2) Push ON within 5 seconds of step 1 3) Push ACC, COAST, RESUME (I am writing this from memory, the order at this step may be different) Each of those button pushes is supposed to be acknowledged by a blink of the CC light. After the last one is pushed, the light should blink once for 'pass' or provide a trouble code, if any. A dynamic response would then follow, with the servo pulling the cable about 10mm.
As I mentioned, in my case the story ends with a single flash after step 2, then nothing. This is with both a defective and a brand new servo that works just fine.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.