Error Code P0325 is described as Knock Sensor Circuit Malfunction, which means problems with the readings from #1 Knock Sensor Circuit. This can mean the readings are too low, too high, erratic, malfunctioning or anything beyond its normal operational window.


Error Code P0325 refers to a problem in the vehicle’s Knock Sensor Circuit. The job of the Knock Sensor is to send a message to the engine computer should one or more engine cylinders “knock”. This “knocking” is characterized by explosion of the air-fuel mixture, which delivers less power and can ultimately damage the engine in the long run.

The vehicle’s computer uses this information to tune the engine and it keep from “knocking”. If the knock sensor malfunctions, and shows that it always knocks, the embedded computer in the vehicle will respond by changing the timing of the engine’s ignition system. Knock sensors are generally bolted or threaded in the engine block. This error code may show up from time to time, or the Check Engine light may be triggered constantly. Other error code related to Knock Sensor problem is P0330.

Common Symptoms

  • Check Engine light is on
  • Drivability problem such as lack or power and hesitation
  • Engine ping upon acceleration
  • Engine is hotter than usual
  • In some cases, the engine may not show noticeable symptoms

Possible Causes

  • Defective Knock Sensor
  • Broken or frayed wires that connects to the sensor circuit
  • Faulty EGR (Exhaust Gas Recirculation) system
  • Lean air-fuel ratio
  • Defective cooling system

How to Check

The PCM (Powertrain Control module) controls the ignition system spark advance and help it achieve maximum power with good fuel economy. The error code is triggered when the Knock Sensor informs the PCM about the knocking on the engine. The PCM then automatically changes the amount of timing advance by delaying it in measured increases. It continues to change until the knock sensor stops sending signal about the pinging or knocking to the PCM.

Error Code P0325 is triggered as the PCM identifies the signal from the Knock Sensor circuit, sensor #1.

To diagnose, take note of the freeze frame data so you will have an idea what operational conditions caused the PCM to trigger the error code.

Next, conduct a visual inspection on the engine and its cooling system, particularly the coolant level or the condition and oil level. This is to verify whether the error code was caused by a failure in the mechanical system or not.

Then, start the engine and make a few revolutions to see if it works normally. This is to ensure there are no severe mechanical errors that may affect the drivability of the vehicle and may cause further damage.

Then, test drive your vehicle. Bring a data streaming scanner with you and pay attention to the #1 Knock Sensor PID as well as the PID for timing advance. How is the sensor #1 working? Is it sending the signal to the engine when it pings? If not, then you should find out why. Sometimes, people tap the engine using a small hammer and observe the knock sensor PID, along with the PID for timing advance.

Check the Knock Sensor

Disconnect the connector from the knock sensor. Then, measure the resistance between the knock sensor connector terminal and engine ground. Is the resistance more than 700 kΩ?

If no, then you can repair the connector and harness to fix the problem.

If yes, then you need to open circuit in harness between knock sensor and ECM connector.

Poor contact in knock sensor connector. Poor contact in coupling connector (B21).

Is the knock sensor installation bolt tightened securely? If yes, then you need to replace the knock sensor. If no, then you just have to tighten the knock sensor installation bolt securely.

How to Fix

  • Check the knock sensor’s resistance and compare it to factory specifications if applicable
  • Check for any broken or frayed wires that lead to the sensor
  • Replace the knock sensor

For more information, diagnosis and repair guides of different error codes, feel free to browse through our website. For professional help, Contact Us,