Frustrated with CEL...

93 3800. CEL light has been on consistently for about 2 months. It set codes 22,26 & 56. I replaced the TPS as well as Crank position sensor and found an injector that was not connected. I hadn't bothered to reset the ECU because the LTC had the shudder problem and the TPS code had it disabled along with OD & cruise control) Van runs fairly well (occasional miss while idling, but otherwise good). I put in some shudder fixx and I then tried to reset the ECU. When I hook it back up and start it, the CEL comes on initially, then turns immediately off, then at the same time that the ABS light turns off, the CEL turns on and stays on. I still don't have OD, LTC or cruise control. I thought it maybe wasn't resetting, so I disconnected the battery for over an hour... same thing, but now it's setting 22, 26, 31 & 56. ECU was replaced (junkyard, I think) last year by previous owner... Any ideas? Do I need a new ECU or is there some other explanation?

26 and 56 are quad drivers...but with OBD1 we do not know which section of the quad is in fault condition. SInce driver B acts on transmission A and B and TCC modulation solenoids and driver A on TCC apply , plus 31 that tells something wrong with trnasmission ....it seems all of that is centered around transmission.
I would check first for proper engagement of transaxle contactors.
DTC22 (www.avigex.ca/xport/dtc22.jpg)
DTC31 (www.avigex.ca/xport/dtc31.jpg)
DTC26 (www.avigex.ca/xport/dtc26.jpg)
DTC56 (www.avigex.ca/xport/dtc56.jpg)
CONNECTORS (www.avigex.ca/xport/transaxleconnector.jpg)
If all of that fails to reveal something, I'd go by your idea about ECU, hoping I can at least try one to confirm or oust this option. A faulty contact switch in the transmission might be a possibility...