Description and Operation: Compensation: Knocking

Fig 1: Mass Air Flow Sensor Function Diagram (Knocking)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

If the engine is knocking, it is corrected by retarding the ignition for the cylinder in question. If knocking persists despite the retardation, the correction factor will be increased. Closed loop will then be deactivated (if it was active) as it would otherwise counter-compensate.

Fig 2: Ignition Retarding Graph

Courtesy of SAAB-SCANIA OF AMERICA, INC.