KSSensor

Knock Sensor (KS)

Group: Engine position and speed

The knock sensor detects pinging (abnormal combustion) inside the cylinders. When it picks it up, the computer retards the ignition timing to protect the pistons.

Contents

What does the KS sensor do?

It is a piezoelectric microphone bolted to the engine block. It produces a small voltage when it picks up vibration at the frequency typical of detonation. The computer advances ignition timing as far as possible to gain power and efficiency, and retards it cylinder by cylinder when the sensor detects knock. Without this signal the computer uses a conservative timing map: the engine runs, but with less power and higher consumption.

Where is it located?

Bolted to the engine block, usually on the intake side under the intake manifold. V engines may have one per bank.

Signal type and reference values

  • Piezoelectric, 1 or 2 wires; it generates its own AC voltage (from millivolts up to about 1 V when struck).
  • Some have a high-value internal resistor (in the megaohm range) so the computer can check the circuit.
  • The tightening torque is critical: over or under-tightening changes its sensitivity.

Values are a guide only: always check the manufacturer's data for your engine.

Symptoms of a bad KS sensor

  • Loss of power and sluggish response.
  • Higher fuel consumption.
  • Audible pinging when accelerating under load (if the sensor fails to detect it and correct it).
  • Codes P0325 to P0334.

How to test the KS sensor step by step

  1. Check the connector and wire: it usually sits under the intake manifold and suffers from heat and oil.
  2. Measure the circuit resistance according to the manual (some sensors should read infinite, others a specific high value).
  3. With the engine idling, tap the block lightly near the sensor with a metal tool and watch the scan tool for ignition retard.
  4. On an oscilloscope, an AC signal should appear when you tap.
  5. When installing it, use the manufacturer's torque and do not add washers or sealant.

Trouble codes related to the KS sensor

Frequently asked questions about the KS sensor

Can the knock sensor cause a loss of power?
Yes. If the computer does not get its signal, it retards the timing for safety and the engine makes less power.
Does higher-octane gasoline cure pinging?
It helps if the engine requires it, but if the pinging comes from carbon buildup, overheating or a lean mixture, you have to fix the cause.

Updated September 25, 2026. Values are a guide only: always confirm them in the service manual for your engine.

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