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Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 1987 Texas Jimmy, May 3, 2006.
Are these 3 items all one in the same?
nossir. all are different sensors
Wire missing from knock sensor...
The knock sensor on the side of my block is half broken off and does not have a wire to it. I have looked and looked and looked, but can't find any trace of a wire even in the wire loom. It looks like it has been like that for a long time. Should i fix it or not worry about it? Could this be part of my problem with code 42/43?
A knock sensor lets the computer set timing by letting it know how much "knock" or detonation the motor is making. It is definetly important and if code 43 is what i think it is, then it is, or is one of the problems.
Okay...I'm looking at a wiring diagram and it shows that a dark blue wire goes from sensor to ESC module on pin E. How does the knock sensor work?
Im not sure HOW the sensor works because it is sealed. I just know it picks up the pings through the metal. You can tap the engine with a hammer and with a timing light, you can see the timing adjust when you tap it.
Knock and detonation are different names for the same symptom. The Electroning Spark Control (ESC) helps the Engine Control Module (ECM) control timing. The system will try to keep the timing as advanced as feasible at all times. However, if the knock sensor "triggers", it sends a signal to the ESC, which then tells the ECM to back off of the timing a few degrees. In a short time, the ECM will try once again to advance the timing to optimum. The process is repeated over and over as you drive.
The knock sensor is tuned to react at a certain frequency, so the sensor itself can be a different part number for various engines.
If your knock sensor is gone, then the ECM will set a code. It periodically advances the timing enough to force a knock, while checking for the ESC to report a knock. If it doesn't detect the knock, the check engine light comes on.
Defenitely will hook the knock sensor up this weekend. Hopefully find the wire in the loom or somewhere else? Maybe the previous owner grounded it out or something. Thanks...
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