Control pressure actuator reading?

[CTDiesel at aol.com]

87 4kq Upon check the control pressure actuator (cpa) sometimes do i get the
mA readings but never long enough to adjust the mixture.  The reading quickly
falls to 0.  Then i go to check it again and there is no reading.  If i let
the car cool off for several hours again i get the reading at first for a few
seconds and then the numbers die off 9-8-7-6-5.....till zero.  What is the
problem?  is the cpa dead?    I'm using a custom wire harness...should i buy
the VW1315A/1 factory harness?

TIA
DJ