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P0325 — Knock Sensor 1 Circuit Fault

P0325 is set when the engine control module does not receive a valid signal from the Bank 1 knock sensor — or the only knock sensor on engines that use one. The knock sensor is a piezoelectric vibration sensor that listens for the characteristic frequency of pre-ignition (detonation) so the ECM can pull timing to protect the engine. With no usable knock signal, the ECM defaults to conservative timing maps, which reduces power and fuel economy.

P0325 means knock sensor 1 circuit fault. A vehicle usually stays drivable short-term with this code, but it should be diagnosed promptly. The most common cause is failed knock sensor element (typically $150–$600). Causes and cost vary by make and model; confirm the root cause before replacing parts.

Severity: moderate powertrain Safe to drive (short term)

Reviewed by MECH AI Editorial · Last verified

What does P0325 mean?

P0325 is set when the engine control module does not receive a valid signal from the Bank 1 knock sensor — or the only knock sensor on engines that use one. The knock sensor is a piezoelectric vibration sensor that listens for the characteristic frequency of pre-ignition (detonation) so the ECM can pull timing to protect the engine. With no usable knock signal, the ECM defaults to conservative timing maps, which reduces power and fuel economy.

What are the symptoms of P0325?

What causes P0325?

Cause Likelihood Estimated repair (USD)
Failed knock sensor element — Most common at 100k+ miles. Some engines bury the sensor under the intake. Most common $150–$600
Damaged or corroded knock sensor wiring or connector Common $80–$350
Loose knock sensor mounting (sensor must be torqued correctly to "hear") Common $20–$100
Rodent damage to knock sensor harness (parked vehicles) Occasional $80–$350
Failed knock sensor sub-harness on GM L83/L86 truck V8s — Specific to GM 5.3 / 6.2 truck V8s — well-documented sub-harness failure. Occasional $200–$600
Internal engine damage producing noise outside the knock sensor band Rare $2,000–$6,000

Repair costs are typical US ranges and vary by make, model, model year, and labor rate. A diagnostic trouble code is a symptom, not a guaranteed failed part — confirm the root cause before replacing anything.

Is it safe to drive with P0325?

In most cases a vehicle stays drivable for short trips with P0325 active, but you should diagnose and repair it promptly. This is a moderate-severity code — ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on your specific make and model.

How to diagnose P0325

  1. Locate the knock sensor — often under the intake manifold

    On many engines (notably GM V6 + V8 truck engines, Toyota 2GR-FE, and most modern Hondas) the knock sensor sits in the engine valley under the intake manifold. Knowing this before starting saves a wasted hour of looking. Consult the service manual.

    Tools: Vehicle-specific service information

  2. Test knock sensor resistance

    Unplug the sensor and measure resistance with a multimeter. Most knock sensors read approximately 90 kΩ to 2.5 MΩ depending on style. Infinite resistance (open) or near-zero (short) confirms a failed sensor.

    Tools: Multimeter, Service spec sheet

  3. Inspect the wiring and connector

    Knock sensor harnesses run close to hot exhaust components and are common chafing victims. Inspect every inch of the harness from the sensor to the PCM connector. Repair any visible damage before replacing the sensor.

    Tools: Inspection mirror, Flashlight, Wire repair supplies

  4. Verify torque specification on the existing sensor

    A knock sensor mounted with the wrong torque cannot transmit vibration efficiently. Spec is typically 15–25 ft-lb. Use a torque wrench, not "tight by feel." Over-torque can crack the housing; under-torque produces false knock-sensor codes.

    Tools: Torque wrench, Service spec sheet

  5. Check for GM-specific sub-harness failure

    On GM L83 (5.3 V8) and L86 (6.2 V8) truck engines, the knock sensor sub-harness running under the intake manifold is a documented failure point — the harness chafes and shorts. Replacement requires intake manifold removal. The sub-harness itself is inexpensive but the labor is significant.

    Tools: Intake manifold gasket, Common hand tools

How do I fix P0325?

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P0325: frequently asked questions

What does diagnostic trouble code P0325 mean?

P0325 is set when the engine control module does not receive a valid signal from the Bank 1 knock sensor — or the only knock sensor on engines that use one. The knock sensor is a piezoelectric vibration sensor that listens for the characteristic frequency of pre-ignition (detonation) so the ECM can pull timing to protect the engine. With no usable knock signal, the ECM defaults to conservative timing maps, which reduces power and fuel economy.

What are the symptoms of P0325?

Check Engine Light is illuminated. Reduced power and slower throttle response. Slight reduction in fuel economy. Engine may run cooler than normal under load. Possible audible engine ping or knock under hard acceleration. No drivability issue in normal driving

What causes P0325?

Failed knock sensor element (most-common). Damaged or corroded knock sensor wiring or connector (common). Loose knock sensor mounting (sensor must be torqued correctly to "hear") (common). Rodent damage to knock sensor harness (parked vehicles) (occasional). Failed knock sensor sub-harness on GM L83/L86 truck V8s (occasional). Internal engine damage producing noise outside the knock sensor band (rare)

Is it safe to drive with P0325?

In most cases a vehicle stays drivable for short trips with P0325 active, but it should be diagnosed and repaired promptly — this is a moderate-severity code. Ignoring it can lead to further damage or a failed emissions test. Specific tolerance varies by make and model.