ECU problem...help!

[Barry Doolan]

My 1991 200qt 20v has been having start problems over the past 2
weeks related to a "Check Engine"signal. Car would start after a long
wait (in the cold of Vermont), check engine light comes on after a
short time, and then no start until another wait of hours. When
brought inside in a warm shop it wouldn't start at all. Codes pointed
to the Hall sensor but the culprit is now narrowed to pin 12 on the
ECU which brings voltage to the Hall sensor. Voltage at this pin
should be 5 volts but it only reads 1 to 1.2 volts. My mechanic
connected a voltmeter to the pin at a time when the voltage read 5
volts (car had been sitting for a day) and it started right up. On
driving the car a short distance the voltage dropped to 1.2 volts and
the check engine light came on. When he returned the car to the shop
it would not start again.

So, it appears to be a malfunction of the ECU? Has anyone had
experience fixing this problem without replacing the ECU? If I do
need to replace, who has a spare?? Mine is the original (I believe)
stock ECU with no upgrades.

I am off on a trip (flying not driving)until Thursday, but I still
would like to see some responses on the listserve for me to read on
my return. In the meantime anyone with a part or advice to my
mechanic can reach Doug at constant at together.net. I am hoping to get
this problem resolved. With  the maple sugar now running in Vermont
the warm days will doom any more drives in my car until this is fixed!

Barry Doolan
Cambridge, Vermont
Black 1991 200qt2Ov