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Home >> BMW >> 2012 >> 535xi GT >> Repair and Diagnosis >> Engine Performance >> Ignition System >> Engine Performance - Functional Description -- F07 >> Engine Performance - Functional Description >> Knock Sensor >> Characteristic curve and setpoint values
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Characteristic curve and setpoint values

The knock sensor shows linear characteristics in the frequency range up to around 20 kHz. The resonance frequency of the sensor itself lies at a significantly higher frequency (greater than 30 kHz). The knocking noises that usually occur in the engine have frequencies of around 7 kHz.

Fig 1: Knock Sensor Output Graph
G09841565Courtesy of BMW OF NORTH AMERICA, INC.
Index Explanation
1 Voltage
2 Signal without knocking
3 Signal with knocking
4 Frequency

Observe the following setpoint values for the crankshaft sensor:

Size Value
Voltage range 4.5 to 5.5 volts
Frequency range 7 to 25 kHz
Maximum output current 20 mA
Ambient temperature -40 °C to 140 °C