Knock Sensor: Testing and Inspection

Fig. 029 - Chart C-4C EST Performance Check:

Procedure
1. Grounding the "Test" terminal causes the system to go to a fixed spark advance which should be different from that obtained with EST operating.
Engine is run at fast idle to get more spark advance. Usually the change is enough so it can be heard in RPM change. If so, it is not necessary to check timing.
2. The check in drive is made because some engines will not have EST operating in P/N.
3. Checks to see if fault is in MAP/VAC system.