engine light has recently stopped working or has never worked since swap?

assuming u are still obd1,hold the ecu so u are looking at the wires going into plugs & the biggest plug(26pin) is on the left.
A4 is the 2nd pin from the bottom left on the 26pin plug.

before u go tossing the ecu,theres other inputs u should check first,but check this output first.

also,touch a ground connection to pin A13(7th from top left 26pin plug) with ignition turned on & see if engine light comes on.