P0325 Code: Diagnosing the Knock Sensor Circuit Issue

Understanding The P0325 Code: Causes, Symptoms, and Solutions

A P0325 code is related to the knock sensor circuit. This article will explore what the P0325 code means, its common causes, symptoms, and how to address it.

What is a P0325 Code?

The P0325 code is defined as: P0325 – Knock/Combustion Vibration Sensor A Circuit. The knock sensor’s primary role is to detect engine knocking or pinging, which is caused by abnormal combustion in the engine cylinders. When the knock sensor detects this issue, it sends a signal to the engine control unit (ECU) to adjust the engine timing and prevent damage.

Specifically, the P0325 code indicates that the knock sensor is not sending the expected signal to the ECU. This could mean that the sensor itself is faulty, the wiring is damaged, or there’s an issue with the ECU. Since the knock sensor is crucial for protecting the engine from damage caused by knocking, it’s essential to address this code promptly.

Don’t automatically replace the knock sensor to fix a P0325 code

Keep in mind that the definition of a P0325 code doesn’t say the sensor is bad; it says Knock/Combustion Vibration Sensor A Circuit, which means it’s a circuit-related code.

Depending on the vehicle, the ECM can test the knock sensor circuit in several ways:

• By purposely causing a knock and then monitoring for a certain knock sensor voltage or
• By supplying a bias voltage to the knock sensor and checking for voltage drop on the circuit.

So, it’s important to check the shop manual for the proper testing procedure.

If you don’t have access to a shop manual start by checking the circuit.

Inspecting the knock sensor circuit

• Disconnect the knock sensor connector and check for signs of corrosion. If you find any, use contact cleaner to remove the corrosion.
• Check the wiring harness for signs of chaffing or an open condition
• Check the harness for continuity between the ECM and the knock sensor connector.
• Check for a bias voltage and voltage drop using a multimeter

How to replace a knock sensor if the circuit tests good

If the circuit tests turn out good, replace the knock sensor to fix a P0325 code. Locate the knock sensor and remove the old one. Install the new sensor and follow the shop manual instructions for the proper orientation and torque specs.

Other causes of P0325L

Keep in mind that the knock sensor can’t tell the difference between shock waves from detonation and shock waves from any other mechanical condition. In some vehicles, loose timing chain guide bolts tend to loosen, causing the guide to vibration and bounce when the engine is running.

©, 2020 Rick Muscoplat