S15/T15 Sonoma P/U 2WD L4-2.2L VIN 5 Flex Fuel (2001)
Knock Sensor: Description and Operation
Operation: Single Wire System
The Powertrain Control Module (PCM) uses a knock sensor to detect abnormal vibration in the engine, detonation/spark knock. Mounted on the engine
block, the knock sensors produces an AC voltage 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 uses the KS signal to calculate an average voltage. Then, the PCM assigns a voltage range above and below
the average voltage value. The PCM checks the KS and related wiring by comparing the actual knock signal to the assigned voltage range. A normal KS
signal should vary outside the assigned voltage range as shown in the NORMAL KS figure, If the PCM detects a KS signal within the assigned voltage
range as shown in the ABNORMAL figure the applicable Diagnostic Trouble Code (DTC) will be set.
