5000CD Quattro Wagon (Canada) L5-2226cc 2.22L SOHC Turbo (MC) (1986)
Knock Sensor Module: Description and Operation
Ignition Knock Regulation
If a cylinder develops ignition knock (detonation), the control unit will "hear" this through the knock sensor. The engine control unit will then retard the
ignition timing by one step of 2.6°. The engine control unit will then check to see if knocking has stopped. If knocking continues, the timing can be
retarded two additional steps of 2.6° each for a total of 7.8°.
Once ignition knock has stopped, the timing will be advanced back to its predetermined value in smaller steps of 1.3°.
Also, to prevent errors, the knock sensor signal will only be processed when the engine is in the operating range where ignition knock can occur. These
are:
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Engine coolant temperature above 70°C (158°F)
^
Intake manifold pressure above 0.7 bar (absolute)
^
Idle switch open