<<The tech recommends that I just plug the vac line going to the shift delay switch on the trans and forget about it. Will this stop the check engine light from coming on?>>
Unfortunately, No.. the CE is computer tripped when the diagnostic mapping test looks at rpm signal..
Many put a BB in the line . [ me included] and once in a while check the code situation.. easy to clear on that DM..
It is one of the feature that tech/owners hate .. I personally use 3rd gear position til my cars are up to temp... so this helps the cat along with keeping my driving preference..
<<Code 26 is the only code present. From this excellent site, I pulled the code and determined it may be the S/o valve.>>
The cod 26 list the SOV valve , but in reality , the code can be
triggered by any part/fault of the system.. the later OBD2 systems can check codes for sov voltages and open coils , but
not on this [OBD1] system.. A code 26 should just read 'Fault in Delay System'...
Many see the code and change the SOV only to find the the fault
Testing of the sov is to get power to it and , while at idle, feel for vac at the outlet port [ hose connection at green trans feed line ] with tranny line disconnected.. this will verify the valve is opening and allowing vac flow....if you put a momentary sw in the power test line , you can rapidly turn the valve on/off and verify if it sticks open/closed... it should shut down solid every time and completely stop vac flow when de-energized...