Celica Coupe - Knock Sensor - Diagrams and Instructions - Page 495
Voltage Check
Example:
A. Ignition SW ON
B. Ignition SW and SW 1 ON
C. Ignition SW, SW 1 and Relay ON (SW 2 OFF)
b. Using a voltmeter, connect the negative lead to a good ground point or negative battery terminal, and the positive lead to the connector or
component terminal. This check can be done with a test a light instead of a voltmeter.