1990 Quattro Coupe, Knock Sensor. How can you check if the knock sensor is bad? My friend use the VAG (blue box) for Audi and we got an error (I don't remember, knock sensor 1... and something). There is anything I should do before ordering a new unit (diagnostic wise).
My car runs very poorly, lack of power and gas mileage is bad. I replaced already few items; I'm still having a problem. I'm sad; I like this car, but it cost a lot to keep it (parts cost a lot.....)
Posts: 758
Joined: 3/9/2004 From: Swamplands of NJ Status: offline
Once after doing some work on my fathers Chevy truck we took it for a test drive and noticed major loss of power. Turned out to be oxidation on the knock sensor connector.
On early GM vehicles one “seat of the pants” test trick that I have heard was while the engine is running, connect a timing light and tap the engine block with a metallic object next to the knock sensor. If the timing gets retarded you know that the system works. Don’t know if the same holds true for Audi’s. For one thing you will probably need to have the engine running above idle and the idle microswitch would have to be at non idle position.
Thanks, I will do some tests over the weekand. The error code I get is "KNOCK SENSOR I-G61 NO SIGNAL" Is this mean that the knock sensor is "dead"? Or I can try something else before buying a new one.
Posts: 758
Joined: 3/9/2004 From: Swamplands of NJ Status: offline
I just read on one Volvo site that the "tap" test doesn't work with Bosch systems but might still be worth a try. I suspect that the sensor is "piezo" type with a ceramic element, when it subjected to vibration or pressure it produces a small amount of electricity. To test one on a bench might be very difficult. Check the connector and wiring first. On my 1991 100Q the corroded connectors are driving me nuts.
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Need help, Knock Sensor... - 
