Knock Sensor (KS) System Description. Cadillac Seville

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2001 🢒 Seville - RHD 🢒 Engine 🢒 Engine Controls - 4.6L 🢒 Knock Sensor (KS) System Description

Purpose

To control spark knock (detonation), a knock sensor (KS) system is used. The KS system allows the powertrain control module (PCM) to adjust ignition timing to eliminate spark knock. This provides optimal driveability and fuel economy under all operating conditions.

Operation

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 AC 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.

Knock Sensor Signal - Normal


(1)	Upper Noise Channel Region
(2)	Noise Channel Average
(3)	Knock Sensor Signal
(4)	Lower Noise Channel Region

Knock Sensor Signal - Knock Present


(1)	Upper Noise Channel Region
(2)	Noise Channel Average
(3)	Knock Sensor Signal
(4)	Lower Noise Channel Region

Diagnosis

A knock sensor module is no longer used to diagnose the knock sensor system. The circuitry is integrated into the PCM.

If the PCM malfunctions in a manner which will not allow proper diagnosis of the KS circuits, DTC P0325 will set.

If the PCM detects a loss of the noise channel, DTC P0327 will set.

When the PCM detects a knock, the PCM will retard the spark timing until the knock goes away. If the knock causes the vehicle to operate on large amounts of spark retard, and the PCM is unable to eliminate the knock, DTC P0326 will set

Problems encountered with the KS system should set a DTC. However, refer to Detonation/Spark Knock in Symptoms-Engine Controls if no DTC sets, and the customer complaint of detonation points to the KS system.