How much does it cost to fix P0325?

DIY repair typically costs $20–$80 for parts. Professional repair runs $150–$400 including parts and labor.

P0325

Powertrain

Low

Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)

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The P0325 code means the Engine Control Module (ECM) has detected a malfunction in the knock sensor 1 circuit on Bank 1. The knock sensor is a small piezoelectric device bolted to the engine block that listens for the metallic pinging or knocking sound caused by abnormal combustion (detonation). When the ECM receives this signal, it retards ignition timing to protect the engine from damage.

When this code is set, the ECM typically cannot properly monitor for engine knock and will default to a retarded (safer but less efficient) timing map. This means your engine will run, but with reduced power and worse fuel economy. You're unlikely to cause immediate engine damage, but prolonged driving without repair means the engine isn't optimally protected against detonation.

The most common fix is simply replacing the knock sensor, which is a relatively affordable repair. However, before swapping the sensor, it's worth inspecting the wiring and connector for damage or corrosion — especially if the vehicle has been in a rodent-prone area. On some vehicles (like many Toyota and Nissan models), the knock sensor is located under the intake manifold, which significantly increases labor time and cost.

Severity

Low — MonitorThis Month

Symptoms

•Check Engine light is on
•Reduced engine power and sluggish acceleration
•Pinging or knocking sounds from the engine under load
•Slightly decreased fuel economy
•Hesitation when accelerating uphill or passing

Likely Causes

Faulty knock sensor40%

The knock sensor itself has failed due to heat exposure, age, or internal degradation, sending incorrect or no signal to the ECM.

Damaged wiring or corroded connector30%

The wiring harness or electrical connector to the knock sensor is damaged, corroded, or has been chewed by rodents, interrupting the signal.

Improper sensor mounting or torque15%

The knock sensor must be torqued to a precise specification on a clean surface. Incorrect installation after prior repairs can weaken signal transfer.

ECM or PCM malfunction10%

In rare cases, the engine control module itself may be misinterpreting a valid knock sensor signal or have an internal fault.

Engine mechanical issue causing excessive knock5%

Actual engine detonation from carbon buildup, low-octane fuel, or overheating can overwhelm the knock sensor circuit.