Knock sensor: Description
To check the plausibility of the knock sensor output it is compared to a modeled knock sensor signal.
If certain coolant temperature, engine speed and load conditions are met then, if the difference between knock sensor output signal and it's modeled value is above a threshold, a relative failure is detected.
An SPI Bus failure for knock can also be detected by the system hardware.
If one of these faults is detected, and certain engine conditions are met, then a limp home strategy can be implemented.