Code 43, ESC Error Without ESC Module: Notes
WARNING: This page is about a different car, the 1990 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
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.