1.15.15 Diagnosis of knock control serial port interface (SPI) monitoring
P16A4 (KRSPInpl)
The knock sensor signals are evaluated and processed in a custom made integrated circuit CC196. This circuit is controlled by the powertrain control module's (PCM) processor and the processed signals are directly accessible for knock control and diagnosis.
The serial peripheral interface (SPI) communication is monitored continuously by evaluating the check words (registers) of the knock sensor's CC196 integrated circuit. The number of errors that occur in a defined observation time frame are counted.
If the error counter exceeds a calibrated threshold during an observation period, a malfunction is detected and a KRSPInpl fault will be set.
The fault path is cleared only when the number of errors is equal to zero.
A KRSPInpl fault is also stored when the Integrated Circuit (CC196) is not completely initialized. In this case only a restart resets the plausibility fault. Activation or deactivation of the diagnosis is allowed only during a reset of the PCM. This ensures a proper execution of the diagnosis.