Knock Sensor
The Knock Sensor (KS) produces an AC voltage at all engine speeds and loads. KS is located on top rear of engine. See Figure or Fig 1 . The PCM then adjusts the spark timing based on the amplitude and frequency of the KS signal. PCM uses the KS signal to calculate the average voltage. Then PCM assigns a voltage value. PCM checks the knock sensor and related wiring by comparing the actual knock signal to the assigned voltage range. A normal KS signal should stay within the assigned voltage range. A fault in the KS circuit may set a DTC. See SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.