Circuit Description
WARNING: This page is about a different car, the 2005 GMC Yukon XL, 2005 Chevrolet Suburban, and 2005 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The knock sensors (KS) produce an AC signal when specific frequencies are detected. When the engine operates, the powertrain control module (PCM) learns a minimum and maximum frequency of noise of normal engine operation. The KS System monitors both KS in order to determine if knock is present. If the KS System determines that excessive knock is present, the PCM retards the spark timing based on the signals from the KS System. The PCM then retards timing until no knock is present.