Checking a knock sensor
Thread Starter
Melting Slicks
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
Checking a knock sensor
Here's part of what I have learned while troubleshooting a Code 43. Understand, my '84 is not stock but runs a '90 speed density ECM from a Camaro thru a SuperRam, while emulating an '87, visually. The 1990 Corvette and one adjacent year runs SD; other C4s are MAF.
Removed from the car, I used my DVOM to check for millivolts of output, measured between the case and the pin; polarity is not important. When I tapped the KS with a socket extension, some millivolts momentarily appeared on the digital display; the quicker I tapped the higher the voltages. The number is unimportant; the generation of voltage is.
Courtesy of Jim at Jim's Performance in Ellicott City, VA (he redid my harness and sold me the sensors and ECM for the engine swap): I asked how to tell if this sensor was the right one; being new and seemingly ok. For an SD system, the resistance between the pin and the case needs to be 4k, not 101k, which is what this near-new one indicated. Perhaps this one's okay for an '84 TBI, but there is no PN on it; just the number '2'; hardly helpful to research what it is.
I hope this helps some of y'all.
Removed from the car, I used my DVOM to check for millivolts of output, measured between the case and the pin; polarity is not important. When I tapped the KS with a socket extension, some millivolts momentarily appeared on the digital display; the quicker I tapped the higher the voltages. The number is unimportant; the generation of voltage is.
Courtesy of Jim at Jim's Performance in Ellicott City, VA (he redid my harness and sold me the sensors and ECM for the engine swap): I asked how to tell if this sensor was the right one; being new and seemingly ok. For an SD system, the resistance between the pin and the case needs to be 4k, not 101k, which is what this near-new one indicated. Perhaps this one's okay for an '84 TBI, but there is no PN on it; just the number '2'; hardly helpful to research what it is.
I hope this helps some of y'all.
Racer
Joined: May 2008
Posts: 312
Likes: 19
Hi,
I can tell you my experience on my 91 SD my car knocked badly when warm. I had a 94 LT1, I pulled that KS and checked the reactions with a VOM. I then installed that 94 KS and everything was good. I had both KS on the bench and compared and the 91 did not respond nearly as well as the 94. Hope this helps.
I can tell you my experience on my 91 SD my car knocked badly when warm. I had a 94 LT1, I pulled that KS and checked the reactions with a VOM. I then installed that 94 KS and everything was good. I had both KS on the bench and compared and the 91 did not respond nearly as well as the 94. Hope this helps.
