1990 Chevy Corvette code 43

CODE 43, ESC ERROR WITHOUT ESC MODULE
Test Number 1) If tapping on engine does not produce a knock signal on "Scan" tester, try tapping the engine closer to the sensor before proceeding.
Test Number 2) The ECM supplies a 5-volt reference signal on the knock sensor line. With knock sensor connected this signal is pulled low to about 2.5 volts. Knock signal, which is an AC signal, rides on this 2.5-volt DC signal.
Test Number 3) This test determines if the knock sensor is faulty or if the ESC portion of MEM-CAL is faulty.
Diagnostic Aids
Check knock sensor signal circuit for a potential open or short to ground. An open knock signal circuit would cause the 5-volt reference to remain high at ECM knock signal terminal. A short to ground in the knock signal circuit would cause the 5-volt reference signal to pull low to near zero volts. Resistance to ground through the knock sensor should be 3300-4500 ohms. Also check for proper installation of MEM-CAL.

Sensors was changed and mem cal
wiring checked ok
ECM at fault

I take it you got the email and the chart I sent to you

good luck
let me know what happens