Kia Optima: Engine Control System / Knock Sensor (KS)

Kia Optima DL3 2019-2024 Service and Repair Manual / Engine Control / Fuel System / Engine Control System / Knock Sensor (KS)


Capacitance (pF)
850 - 1,150

Description and operation

Knocking is a condition characterized by undesirable vibration and noise and can cause engine damage.

Knock Sensor (KS) is installed on the cylinder block and senses engine knocking.

When knocking occurs, the vibration from the cylinder block is applied as pressure to the piezoelectric element.

At this time, this sensor transfers the voltage signal higher than the specified value to the ECM and the ECM retards the ignition timing.

If the knocking disappears after retarding the ignition timing, the ECM will advance the ignition timing.

This sequential control can improve engine power, torque and fuel economy.

Components and components location
Components Location

1. Knock Sensor (KS)

Schematic diagrams
Circuit Diagram

Harness Connector

Repair procedures

The engine control system can be more quickly diagnosed for troubles by using the vehicle diagnostic system (KDS). (Refer to "DTC guide")

KDS provides the following information.


Self diagnosis : Inspects and displays diagnostic trouble code (DTC)


Sensor data : Checks the system input/output value status


Forced operation : Checks the system operating status


Additional function : Controls system options, zero point adjustment and other functions

Component Inspection

Turn the ignition switch OFF.


Disconnect the knock sensor connector.


Measure resistance between the knock sensor terminals 1 and 2.


Check that the resistance is within the specification.

Specification: Approximately. 4.87 MΩ [20°C (68°F)]


Disconnect the negative battery terminal.


Remove the intake manifold.

(Refer to Engine Mechanical System - "Intake Manifold")


Remove the knock sensor (A) after loosening the mounting bolt.

Knock sensor mounting bolt:

18.6 - 23.5 N·m (1.9 - 2.4 kgf·m, 13.7 - 17.4 lb·ft)


Install the component with the specified torque.

Note that internal damage may occur when the component is dropped. In this case, use it after inspecting.


Install in the reverse order of removal.

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