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P0325: Knock Sensor Circuit Malfunction (Sensor 1, Bank 1)

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What is P0325?

The P0325 code is a generic diagnostic trouble code (DTC) defined as “Knock Sensor Circuit Malfunction (Sensor 1, Bank 1).” DTC P0325 occurs when your engine control module (ECM) or powertrain control module (PCM) receives improper readings from the knock sensor circuit.

Vehicles with internal combustion engines require a balanced supply of air and fuel that burns in small, regulated pockets. If there’s an imbalance in the supply of air and fuel, your engine may produce a pinging or tapping sound known as “engine knock” or “spark knock.”

The knock sensor (bolted or threaded into the cylinder block) detects these sounds or vibrations from abnormal combustion and reports it to your vehicle’s engine control module.

The ECM uses the information from the knock sensor circuit to tune the engine or change the ignition timing (also known as knock retard), thereby preventing an engine knock.

However, if the knock sensor circuit is malfunctioning, your engine computer will turn on the Check Engine Light on your dashboard and log the P0325 code.

Note: The engine knock or detonation could also be due to regular fuel instead of premium fuel. That’s because premium fuel has a higher octane rating (meaning better fuel quality) and is less susceptible to producing an engine knock. 

Common symptoms

The following symptoms may accompany a bad sensor circuit and code P0325: 

1. An Illuminated Check Engine Light

When your powertrain control module detects a knock sensor circuit malfunction, it’ll turn the Check Engine Light on your dashboard and log DTC P0325.

The Check Engine Light on your dashboard is one of the most important signs of engine code P0325 (though not specific to this code alone), especially since this error code may not pose any immediate drivability issues. 

2. A Noticeable Lag While Accelerating

When a knock sensor malfunction is detected, the ECM may automatically enter safe mode.

While this helps protect the engine from damage, it also throws off the ignition timing, resulting in noticeable lag during acceleration.  

3. Abnormal Engine Noise  

Unusual engine noise while running is a fairly common sign of engine issues — especially if you have trouble code P0325 that’s not due to a faulty knock sensor.

An abnormal sound while idling could signify a critical underlying engine condition that must be checked and fixed soon. If left unaddressed, it can lead to severe engine damage. 

4. Increased Fuel Consumption

When the ECM detects the knock sensor code P0325, it defaults to preset values, preventing engine damage.

You may notice a spike in fuel consumption because the engine burns fuel inefficiently when this happens.

Can I still drive?

While the knock sensor code P0325 may not pose any immediate drivability concerns, it can severely affect your vehicle’s performance if left unchecked.

In some cases, the ECM will retard ignition timing to prevent engine damage, resulting in your vehicle experiencing a lack of engine power.

So, if you observe the Check Engine Light on your dashboard or any other P0325 code symptoms, you should get the knock sensor diagnosed and fixed.

P0325 causes

Many potential factors can cause code P0325. 

Here are some of the main triggers: 

  • A bad knock sensor or knock sensor malfunction
  • Damaged or frayed knock sensor circuit wiring or a poor connection in the wiring harness 
  • A faulty engine coolant system
  • An imbalanced supply of air and fuel to the engine cylinder
  • A bad spark plug (while this is not common, it’s still a possible cause) 

Diagnosis

Diagnosing the P0325 code requires specialized equipment and technical knowledge. 

Here’s a quick look at how a skilled technician would diagnose this error code:

  • With the help of an OBD2 scan tool, the technician will first verify if the powertrain control module has logged fault code P0325. They’ll also check if any other code is present and fix that first.
  • They’ll then clear the existing fault codes and the Check Engine Light, do a road test and see if it resurfaces.
  • Next, the mechanic will use the scan tool to check the knock sensor AC voltage, ensuring it’s within the specified range.
  • They’ll also check if the coolant temperature sensor voltage sends false readings to the ECM, possibly causing a lean running condition and spark knock.

Then, the mechanic will remove the power steering pump and visually check the wire and wiring harness using the wiring diagram. If the issue remains unresolved, they’ll check for a fault with the engine control module, although this is a very unlikely cause.

Possible repairs for P0325 & Costs

Depending on the diagnostic results of code P0325, you may need to apply one or more of the following solutions:

  • Fix any connection issues with the knock sensor wire and knock sensor connector
  • Replace the faulty knock sensor with an OEM sensor (ensuring grease or rust is removed from the engine block first)

Repair costs

The repair costs for code P0325 can vary significantly depending on whether you need a new sensor or a replacement connector (wire harness.)

Here are the average estimated costs for some replacement components, including labor charges:

  • Knock sensor wire harness: $15 to $70
  • Knock sensor: $300 to $400
  • Temperature sensor: $400 to $450

3 P0325 Trouble Code FAQs

Here are some routine questions and answers associated with the knock sensor code P0325: 

1. What Is A Knock Sensor?

The knock sensor can be described as a small listening device located outside the engine block (also called cylinder block) or underneath the intake manifold.

Its key function is to pick up vibrations and sounds from the engine block, which are then converted and sent as an electronic signal to the engine computer. 

2. Is The Code P0325 More Common With A Certain Brand Of Vehicles?

While the code P0325 can occur with any vehicle, it’s statistically more common with the following brands:

  • Acura
  • Chrysler
  • Ford motor company (Ford Mondeo, Focus)
  • Honda motor company (including the Honda Accord, Odyssey, Pilot, SRV, Fit, Civic, Element)
  • Toyota motor corporation (Toyota Avensis, Camry, Corolla)

3.  What Are The Other Faults Codes Related To The DTC P0325?

Here are some of the trouble codes commonly associated with the P0325 code:

  • P0326: Knock Sensor 1 Circuit Range/Performance (Bank 1 or Single Sensor)
  • P0327: Knock Sensor 1 Circuit Low Input (Bank 1 or Single Sensor)
  • P0328: Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)
  • P0329: Knock Sensor 1 Circuit Intermittent (Bank 1 or Single Sensor)

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