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Here is what I have found out about the knock sensor Posted by Gene N [Email] ![]() ![]() ![]() In Reply to: I think we need Anders help with this, Robert Kaplan, Tue, 6 Aug 2002 10:59:40 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The knock sensor is just a piezoelectric microphone. The DI/APC is "listening" for the high frequency components consistent with a detonation event. Because it is not like a NTC temperature sensor with a specific resistance range, the DI/APC can't really tell directly if the microphone is defective or disconnected. However, if the DI/APC gets no signal at all after the running the engine for 5 minutes, it turns on the check engine light and enters a fault in the DI/APC memory. (The engine may have to be under load to keep an idling engine from tripping the fault.) The check engine lamp may stay on if the condition persists, or go out if the sensor comes back on.
The error will cause the check engine light to flash 4 times if you have a problem with the knock sensor and turn on the ignition without starting the car. The error condition can be cleared by pulling the DI/APC test fuse (23 I think) clearing the DI/APC memory. At that point you would have to do a new adaptation run to restore performance to its maximum levels.
My information is based on the DI/APC section and some experimentation when I had a flakey knock sensor.
posted by 140.188.64...
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