OBD-II Code · Sensors
P0325
Knock Sensor 1 Circuit Malfunction
Severity
medium
Worth booking. It costs fuel, emissions or comfort until it is fixed.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$150–$500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
The knock sensor isn't reporting engine knock correctly.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Reduced power
- Pinging noise under load
- Reduced fuel economy
Likely causes
- Failed knock sensorMost common
- Wiring issue
- Use of wrong fuel grade
Read the full diagnostic procedureP0325 indicates a general circuit fault on knock sensor 1 (bank 1) - the PCM is not seeing a usable signal at all.
P0325 indicates a general circuit fault on knock sensor 1 (bank 1) - the PCM is not seeing a usable signal at all. The cheapest-first ladder depends on sensor type. Piezo-flat-washer sensors (Toyota, Honda, most modern Asian engines) should show roughly 4 to 5 megohms across the sensor terminals with the connector unplugged. Resonant tuned sensors (most GM LS, older Ford) typically read about 90 to 110 kohm. With the sensor connected and engine running, backprobe the signal wire to ground with an AC-coupled scope or DMM on AC volts - a healthy piezo sensor produces about 20 mV to several hundred mV AC during normal combustion noise, with sharp spikes during a tap on the engine block near the sensor. Verify the shield/ground side is intact, since knock sensors are typically a shielded twisted pair.
Caveat
never condemn a knock sensor on a GM LS truck (4.8/5.3/6.0) without first inspecting the under-intake engine harness - this is the #1 misdiagnosis in GM truck shops and the actual fault is harness corrosion, not the sensor.
Vehicle-specific patterns1999-2007 GM Silverado/Sierra/Tahoe/Yukon/Suburban 4.8/5.3/6.0 LS is the epidemic platform - knock sensors live in the lifter valley UNDER the intake…
- 1999-2007GM Silverado/Sierra/Tahoe/Yukon/Suburban 4.8/5.3/6.0 LS is the epidemic platform - knock sensors live in the lifter valley UNDER the intake manifold and the foam mat traps moisture against the harness, corroding the connectors and pigtails. GM TSB 02-06-04-037 covers the harness replacement.
- 2003-2008Honda Accord/Element/CR-V K24 has a known knock sensor internal failure around 100k-150k miles.
- 2005-2009VW/Audi 2.0T (BPY) suffers chafed knock sensor harness against the cylinder block.
- 2007-2013BMW N52/N54 sets P0325 from cracked knock sensor connectors under the intake.
Estimated repair$80 to $700.
Look up another code
P0325 — frequently asked
What does a P0325 code mean?
The knock sensor isn't reporting engine knock correctly.
What causes a P0325 code?
Common causes: Failed knock sensor; Wiring issue; Use of wrong fuel grade.
What are the symptoms of a P0325 code?
Typical symptoms: Check engine light; Reduced power; Pinging noise under load; Reduced fuel economy.
Is it safe to drive with a P0325 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $150-$500.
How do I diagnose a P0325 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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