Understanding the Honda P0325 Code: Causes and Solutions

Troubleshooting and Fixing the Honda P0325 Code

A Honda P0325 code specifically refers to a malfunction in the knock sensor circuit, which can affect your vehicle’s performance and efficiency. Understanding and fixing this code is crucial to maintaining your car’s optimal operation. This guide will walk you through diagnosing and repairing a P0325 code in your Honda.

Understanding What a Honda P0325 Code Means

The P0325 code is triggered when the Engine Control Module (ECM) detects a problem with the knock sensor circuit. The cause can be a faulty wiring harness, a connector/terminal issue, or a bad knock sensor.

The knock sensor contains paper-thin piezoelectric crystals that create a voltage when compressed. Strong engine knock and ping vibrations compress the crystals in the sensor to different degrees, sending different voltage signals to the ECU. The ECU can then make any required changes to the air/fuel mixture and ignition timing to keep it running safely. Human listeners can detect any major knocking issues, but the knock sensor can detect almost imperceptible levels of knock outside an acceptable range.

How the ECM sets a Honda P0325 Code

The knock sensor is a piezo ceramic element that generates electrical signals when it detects a vibration strong enough to represent a knock in the cylinder. When the engine is running, the ECM expects to see a variation in the signal from the knock sensor. If the signal doesn’t vary during a set period of time, the ECM stores a P0325: Knock Sensor (KS) Circuit Malfunction trouble code and turns on the check engine light.

How to diagnose and fix a P0325 code

The ECM supplies a very low reference signal to the knock sensor on the red/blue wire. Start by checking for a reference voltage of around 0.03 volts in the knock sensor connector with the knock sensor connector unplugged. If you don’t see that voltage, check the wiring harness and terminals from the ECM to the connector

Next, reconnect the knock sensor connector and probe the sensor wire back. Connect your scope and watch the pattern with the engine running idle and at 3000 to 4000 RPM again. The voltage should be very low at idle, around +1 volt to -1 volt. If you don’t see those voltages, check the wiring harness condition. If the harness is good, replace the knock sensor.

The knock sensor is mounted on the cylinder block and detects engine knocking. The vibration caused by knocking is converted into electrical signals through the piezo ceramic element. The engine control module (ECM)/powertrain control module (PCM) controls the ignition timing based on the electrical signals. If the signal from the knock sensor does not vary for a set time period, the ECM/PCM detects a malfunction and stores a DTC.

How to replace a knock sensor

Consult your vehicle’s shop manual because the sensor’s torque and orientation are critical to avoiding a repeat Honda P0325 code. For screw-in sensors, use a deep socket and a torque wrench. For bolt-on sensors, orient the sensor according to the shop manual and use a torque wrench to tighten the hold-down bolt.

Honda issues a service bulletin for the P0325 and P1009 codes.

Shops are reporting a high incidence of Honda P0325 and P1009 trouble codes. The Honda P1009 is an enhanced manufacturer specific code defined as: P1009 Variable Timing Control System Advance Malfunction – Automatic Transmission. Honda has issued a service bulletin #08-089 to address the P1009 issue on the vehicles listed below.

Honda P1009 vehicles affected by service bulletin #08-089

2005-08 CR-V
2009 CR-V 2WD VIN 5J6RE38..9L000001 through 5JRE38..9L000019, and 3CZRE38..9G70000a through 3CZRE38..9G700490, and JHLRE38..9C000001 through JHLRE38..9C997328
2009 CR-V 4WD VIN 5J6RE48..9L000001 through 5J6RE48..9L000025, and JHLRE48..9C000001 through JHLRE48..9C007328

Fix for Honda P1009

The service bulletin advises techs to update the software in the above-mentioned vehicles to correct the flaw in the software that misinterprets the VTC inputs and sees them as a fault in the VTC system.

©, 2019 Rick Muscoplat