Check engine light

[Steve & Kathy Enfinger]

1991 8V92 DDEC II. "Check engine" light does not go out after 5 seconds
when ignition turned on ... tachometer inoperative. Engine runs fine
but speed restricted to 37 mph (computer I assume). Problem is
intermittent. After coach sits a few hours when the ignition switch is
turned on both the "stop engine" & "check engine" lights will go out
(normal sequence) & tach works & engine operation & speed are normal.
Then when switched off & re-started only the "check engine" light comes
on constantly ... "stop engine" light never comes on ... tach inop ...
speed restricted.

I am suspect of a ground problem but don't have a clue where to start
the search. I'm also suspect of the DDEC II unit but want it to be
something much more simple ($$$$).

All fluids normal, no noises, leaks, or performance issues when "check
engine" light is off ... but as you can imagine ... 37 mph is very
restrictive for most travels.

Steve & Kathy Enfinger
'91 WBSA PT40