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Knock Sensor 392502B000: What It Does and When to Replace It

The 392502B000 knock sensor is a piezoelectric accelerometer bolted to the block of Hyundai's Gamma 1.6L MPI engine family — codes G4FC, G4FD, and G4FG. Its whole job is to listen for detonation. When knock starts, the ECU pulls ignition timing back instantly, before your connecting rod bearings absorb the damage.

If your Veloster, Rio, Soul, or Accent has stored a P0325, P0326, or P1326 code, this is the part in question. The direct-fit 392502B000 knock sensor on Koeep is built to OEM specification for these engines and needs no ECU recalibration after installation.

Fitment and Cross-Reference Numbers

One sensor covers four platforms that share the Gamma 1.6L engine:

• Hyundai Veloster — 2010–2017
• Kia Rio — 2012–2020
• Kia Soul — 2010–2019
• Hyundai Accent — 2012–2019

Match it by any of these interchange IDs: SU13907, KS392, KS392T, 5S12492, 2KNC0108, KNK320. The OEM reference number is 39250-2B000, so check the stamp on your old sensor before ordering.

Plenty of sellers list this part under the OEM-format number only. If that is how you searched, the same sensor is stocked as a single unit on the 1Pcs Knock Sensor 39250-2B000 listing — identical part, same Veloster, Rio, and Soul coverage.

How the Sensor Is Built

The PZT Element

Inside sits a Sonox P502-grade PZT (lead zirconate titanate) piezoceramic ring — PZT-5A class — sandwiched between a seismic mass and the sensor housing. The design is non-resonant with a flat response across 5–20 kHz, which lets the ECU separate normal combustion harmonics from destructive detonation events.

That flat response is purpose-matched to the Gamma engine's combustion acoustics, built around a 78 mm bore × 85.4 mm stroke. This is also what makes the sensor KSDS-compatible, covered below.

Housing, Sealing, and Noise Rejection

The housing is zinc-plated alloy steel with a salt-spray resistance rating over 96 hours per ISO 9227. That matters in coastal regions and northern-tier states where corrosion eats engine bays. A high-temperature silicone-sealed connector boot resists oil vapor, coolant exposure, and thermal cycling — real conditions in the Veloster's compact engine bay and the Soul's high-load urban duty cycles.

The harness is a shielded twisted-pair design that rejects EMI/RFI from adjacent ignition coils and hybrid-system inverters, in line with ISO 7637-2 (2026 revision) transient immunity standards. The 2-pin connector carries an IP67K ingress rating, so high-pressure under-hood washing will not corrupt the signal path to the ECU.

Specifications

Symptoms of a Failing Knock Sensor

On high-mileage Gamma 1.6L engines, the failure pattern is progressive. Watch for these in order:

1. Audible pinging under load at 2,000–3,500 RPM, especially on 87-octane fuel in hot ambient conditions.
2. Fuel economy down 10–15% — with no signal, the ECU defaults to a conservative retarded-ignition timing map.
3. Hesitation and power loss during acceleration, obvious on the Soul's stop-and-go cycles and the Veloster's mid-range pull.
4. Check engine light with P0325–P0328 or P1326 stored.
5. KSDS limp mode (P1326) — RPM capped near 2,000–2,500, vehicle speed restricted.

A mileage drop is not always the knock sensor. The upstream oxygen sensor is the other usual suspect, and the oxygen sensor 39210-2B220 for the 2012–2017 Accent, Veloster, Rio, and Soul covers the same platforms if your scan points at fuel trim instead of knock.

DTC Codes Mapped to This Sensor

Knock sensor circuit faults fall in the P0324–P0334 range under SAE J2012 / ISO 15031-6. On the single-sensor Gamma 1.6L (Bank 1), expect one of these:

• P0324 — Knock Control System Error, a system-level fault often KSDS-related.
• P0325 — Knock Sensor 1 Circuit Malfunction: open circuit, corroded connector, or internal sensor failure.
• P0326 — Circuit Range/Performance: signal outside the expected voltage window.
• P0327 — Circuit Low Input: shorted to ground or degraded piezoceramic output.
• P0328 — Circuit High Input: shorted to the voltage reference or excessive mechanical noise.
• P1326 — Hyundai/Kia proprietary KSDS fault. Limp mode is active; deal with it immediately.

Concretely, the ECU monitors three things: circuit continuity (the P0325 open-circuit check), signal amplitude against the calibrated 0.3–4.8V AC window (P0326, P0327, P0328), and the proprietary P1326 threshold for vibration signatures tied to rod bearing degradation. All codes are readable via SAE J1979 Mode $03 and clearable via Mode $04.

If the trail leads beyond the sensor, the Starters, Alternators & ECUs collection covers the electrical and engine-management hardware these platforms share.

KSDS Compatibility: Campaign 966 and 953

The 392502B000 is fully compatible with the Hyundai/Kia Knock Sensor Detection System, including the Campaign 966 and Campaign 953 software updates. KSDS runs signal-processing algorithms on the sensor's raw AC waveform, hunting for vibration signatures that indicate connecting rod bearing wear.

This sensor produces the identical frequency-domain signature the algorithm expects, so no ECU reflash or dealer calibration is needed after install. That detail matters: aftermarket sensors with mismatched piezoceramic response curves are known to trigger false P1326 limp-mode events.

Installation Steps and Torque Spec

1. Disconnect the negative battery terminal and wait 5 minutes for capacitor discharge.
2. Locate the sensor on the engine block, beneath the intake manifold on the cylinder bank side, between cylinders 2 and 3.
3. Release the 2-pin shielded connector by depressing the locking tab — never pull on the wires.
4. Remove the old sensor with a 24 mm deep-well socket.
5. Clean the mounting boss thoroughly. No sealant, thread-locker, or anti-seize — these interfere with the metal-to-metal acoustic coupling accurate knock detection depends on.
6. Install the new sensor and torque to 20–25 N·m (15–18 lb-ft) with a calibrated torque wrench.
7. Reconnect the harness, clear all DTCs with an OBD-II scanner, and run a key-on/engine-off (KOEO) self-test.

Stay under 30 N·m. Over-torquing preloads the piezoceramic element and shifts the sensor's resonance frequency, producing false knock detection or missed detonation events — both worse than the fault you started with.

Frequently Asked Questions