How to test a knock sensor - GM (low power condition)

GM 3100 engine, knock sensor test.
This engine had a slight rod knock or upper engine noise that was causing the knock sensor to record a false signal. The computers reaction was to retard ignition timing in an attempt to quiet the knock sensor down. The result was a severe low power condition at times.
The main take away with this case study is for low power complaints, don't forget to look at your knock sensor activity as a possible cause.

Engine Performance Diagnostics chapter 10 pages 6-7

Symptoms
- intermittent low power
- runs good cold and at WOT
- knock retard degrees on scan data goes very negative

Fix
- internal engine noise was causing false knock sensor activity
- left knock sensor disconnected (car was not worth repair cost to fix the engine)

Tests shown
- how to test a knock sensor
- how to determine the cause of a low power condition

Tools used
- scan tool
- labscope
- back-probing tools

Playlist
- (Chapters 9, 10 and 11) The 5v Reference and Signal Circuit Quick Tests
https://www.youtube.com/playlist?list=PLAFYVCyenqcpP9ykkWb2D16nVEjyQ1eTZ

Related Videos
- How to test a Knock Sensor (P0328) - Subaru
https://youtu.be/2-JBTwOvD9w
- How to test a Knock Sensor (P0328) - Nissan

For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
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