i believe, IIRC the solenoids are powered on the positive side by the EEC relay and controlled by the computer on the negative side. which means between ground and one side of the EGR TAB TAD solenoids you should see battery voltage, with key in on position regardless of engine running. the other side of circuit should be grounded when the computer commands these solenoids to operate. big deal here is if the EEC power circuit which powers fuel injectors, IAC solenoid, and the afformentioned valves is not at battery voltage, this could cause these symptoms and would not be a computer issue.
if you jumper your self test connector, key on engine off, let it go thru all its codes, it will long pause, then the check engine light will illuminate on. at this point, push down the gas pedal to floor momentarily, under the hood you should hear these solenoids all engage, push again to disengauge.
find the common EEC 12v line, on one of these solenoid valve connectors while disconnected. test against bat NEG. should be very close to battery voltage. should not deviate from it by more than 0.2v
plug it in, do you hear the solenoid click on? this means the
the solenoids are in on position, or grounded by the computer. if no click when connector is plugged back in, go to the throttle and momentarily open throttle. opposite side of connector should be the sinking side, or grounding side of the circuit. test between it and bat positive, you should see within 1.5v of battery voltage. the sinking side of circuit looses a little voltage due to losses in the transistor.
if i had access to my laptop right now i'd be more helpful, with giving you actual wire colors. i'm on my phone and don't have access to an FSM.
ruling out poor voltage on your EEC relay circuit, (V+) is important. if you see 9v ish voltage, or inconsistent voltage at the solenoids, at the fuel injector connectors, at the IAC valve, between ground and the EEC relay V+, this could cause a lot of problems.
this is just one of many things to troubleshoot.
side note, if you have access to any junkyards nearby, with an eecIV computer for your engine/transmission combo, its very likely going to work just fine. in my experience, very little changed on EECIV computers besides the black/gray ignition modules and the signature PIP signal, or if you have a E4OD trans, and even at that, they work but often just set codes. you must have an E4OD computer to do that transmission. manual and C6 trans computers are nearly identical.
i tend to avoid impediance based tests, prefer voltage based testing as a very poor connection can still appear okay on a meter.
EDIT:
i have recapped these computers before, beware of the silicone gunk they put on the circuit boards, it may have prevented a good solder connection. i have done a number of them over the years and was subtly surprised to find that it didn't solve the issue, that it had nothing to do with the computer but was an overlooked thing elsewhere.
hope any of this helps. i'll try to check back in.
