Knock Sensor Detection System (KSDS) Malfunction

What it means

This is a Hyundai-specific code; the same number can mean something different on other makes. Hyundai added KSDS software to certain Theta II engines; it uses the knock sensor to detect vibration that may indicate early wear of the crankshaft or connecting rod bearings. When it detects this, the check engine light usually flashes, the code is stored, and the car may enter limp mode with reduced power and limited RPM; contact the dealer promptly.

Models covered: Hyundai Theta II 2.0T and 2.4 engines fitted with the KSDS software update, mainly around 2011–2019 (e.g. Sonata, Santa Fe, Tucson).

Related codes: P0325P0326P0327P0328P0300P0521

Symptoms4

• The check engine light flashes or comes on suddenly.
• A clear loss of power and limited engine speed in limp mode.
• A rhythmic metallic knock from the bottom of the engine that rises with RPM in some cases.
• There may be no obvious noise at an early stage, because the system detects vibration before the driver hears it.

Possible causes5

• Connecting rod or crankshaft bearing wear, which the system is designed to detect.
• Low oil level or overdue oil changes that speed up bearing wear.
• A faulty knock sensor, connector or wiring giving a false signal.
• A knock sensor that is loose or not tightened to the correct torque.
• Other mechanical vibration in the engine or its accessories picked up by the sensor (less common).

How to diagnose5

1. Check the oil level right away, and do not run the engine for long if it is very low or a clear knock is heard.
2. Visit a Hyundai dealer for the approved KSDS inspection and a read of the codes and stored data.
3. The technician checks engine noise and oil pressure and may inspect the oil and filter for metal debris.
4. The knock sensor circuit, connector and mounting are checked to rule out a simple electrical fault.
5. The dealer checks by VIN whether the car is covered by service programs or extended warranty in its market.

How to fix5

1. Top up with the oil type and viscosity specified by Hyundai if low, then head to the dealer.
2. Repair the knock sensor connector or wiring, or replace the sensor and tighten it to the correct torque if confirmed faulty.
3. Update the engine computer software if the dealer recommends it.
4. Replace or repair the engine per the dealer procedure if bearing wear is confirmed.
5. Clear the codes after the repair and confirm the code does not return on a road test.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low when the knock sensor or its wiring is the cause, and reaches the top of the range, beyond the usual price table, when the engine is replaced. Service programs or extended warranties that Hyundai ran in some markets may cover this repair; the dealer checks this by VIN.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions