Knock Sensor 1 Circuit (Bank 1 or Single Sensor)

What it means

The engine computer (ECU) has detected an electrical problem in the knock sensor 1 circuit. The knock sensor 1 listens for engine knock (detonation) so the ECU can retard ignition timing before damage happens. The signal is missing or outside the range the ECU will accept.

Symptoms

• Check engine light on
• Reduced power and fuel economy (the ECU retards timing to be safe)
• Audible pinging or knocking under load in some cases

Probable causes

Most likely first

1. 1Damaged or unplugged connector
2. 2Open or shorted wiring
3. 3Failed sensor
4. 4Damaged reluctor (tone) ring

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the knock sensor 1 connector and wiring (bolted to the engine block, often under the intake manifold). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the knock sensor 1 reading on live data. Watch knock retard on live data while driving under light load. It should stay near zero on a healthy engine with the right fuel.
4. 4Check the sensor resistance (for 2-wire sensors) or power and ground (for 3-wire Hall-effect sensors). Watch the signal on an oscilloscope or graphing meter while cranking or driving; it should be a clean, regular pattern.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Repair the damaged wiring or connector
• Replace the knock sensor 1
• Clear the code and test drive to confirm the repair

Videos about P0325

Diagnostics

The Used Car Project CRV Had a P0325

EricTheCarGuy · 18 Sept 2026