Sunfire L4-144 2.4L DOHC VIN T SFI (2001)
Knock Sensor: Description and Operation
Operation: Single Wire System.
The PCM uses a Knock Sensor (KS) to detect abnormal vibration in the engine (detonation/spark knocking). Mounted in the engine block, the knock
sensor produces an IAC signal at all engine speeds and loads. The PCM then adjusts the spark timing based on the amplitude and frequency of the KS
signal. The PCM calculates a normal level of engine noise (noise channel) from the KS signal. The noise channel consists of an upper and lower region.
A normal KS signal should vary within the noise channel as shown in the Knock Sensor Signal - Normal. A KS signal outside the noise channel, as
shown in Knock Sensor Signal - Knock Present, indicates spark knock. The PCM will then adjust the spark timing to eliminate the engine knock.
