P0325 – Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)

What does P0325 mean?

The knock sensor circuit on Bank 1 has a malfunction. The knock sensor listens for engine detonation (pinging) so the computer can retard ignition timing to protect the engine. Without a working sensor, the computer conservatively retards timing, costing power and efficiency.

What causes P0325?

Listed from most to least common:

1. 1Failed knock sensor
2. 2Damaged wiring or corroded connector at the sensor
3. 3Poor ground connection
4. 4Actual engine knock from low-octane fuel or carbon buildup
5. 5Rarely, an ECM fault

Code breakdown

Common symptoms

• Check engine light on
• Noticeable loss of power and throttle response
• Reduced fuel economy
• Possible pinging or knocking sound under acceleration
• Engine may feel sluggish under load

How to diagnose

1. 1Inspect the knock sensor wiring and connector — these sensors sit in hot, exposed locations and wiring failure is common.
2. 2Measure knock sensor resistance and compare against specification.
3. 3Check the sensor's ground connection for corrosion.
4. 4Rule out genuine engine knock by verifying correct fuel octane and listening under load.
5. 5Confirm the sensor is torqued correctly — knock sensors are torque-sensitive and will read incorrectly if loose or overtightened.

The engine loses some performance and efficiency because the computer defaults to safe timing. Real detonation also goes undetected, which can damage the engine under load.

Common fixes and estimated costs

Costs are rough US estimates including parts and labor. Actual pricing varies significantly by vehicle, region, and shop rates.

Good to know

On many V6 and V8 engines the knock sensor sits under the intake manifold, which makes replacement labor-intensive and expensive despite the part itself being inexpensive. Torque specification matters — an improperly torqued sensor will not read correctly.

Related codes