Knock Sensor
WARNING: This page is about a different car, the 1997 Mazda Millenia. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect knock sensor connector. Using ohmmeter, measure resistance between knock sensor terminal "A" (Red wire) and knock sensor body. Resistance should be about 560,000 ohms at 68°F (20°C). If resistance is not as specified, replace knock sensor.