What Does P0325 Mean?
A malfunction has been detected in the knock sensor 1 circuit on Bank 1 (or the single sensor on inline engines). The knock sensor is a piezoelectric element that detects engine vibration frequencies associated with detonation, allowing the PCM to retard ignition timing to prevent engine damage. Without a functioning knock sensor, the PCM will default to a conservative timing map, resulting in reduced power and fuel economy.
Common Causes
30%
Failed knock sensor with no piezoelectric output
25%
Open or high-resistance wiring in the knock sensor circuit
20%
Corroded or loose knock sensor connector preventing proper signal transmission
15%
Knock sensor improperly installed — wrong torque, wrong gasket, or cross-threaded
10%
PCM knock sensor input circuit fault
Diagnostic Steps
1
Measure the knock sensor resistance at the sensor connector: typical values are 50K–600K ohms depending on the manufacturer. An open circuit (infinity) confirms a failed sensor.
2
With the scan tool, monitor the knock sensor signal while tapping the engine block near the sensor with a small hammer — the signal should spike. No response confirms a circuit or sensor fault.
3
Inspect the knock sensor wiring for damage, especially where the harness routes near the exhaust manifold or other heat sources that can melt insulation.
4
Verify the knock sensor is properly torqued to manufacturer specification (typically 15–22 ft-lbs). Remove and inspect the sensor face for cracks or contamination from coolant or oil leaks.
5
Check for continuity and proper shielding on the knock sensor circuit from the sensor to the PCM. The shield drain wire should be grounded at one end only.
Estimated Repair Cost
$100 - $400
Parts + labor, varies by vehicle and location
A malfunction has been detected in the knock sensor 1 circuit on Bank 1 (or the single sensor on inline engines). The knock sensor is a piezoelectric element that detects engine vibration frequencies associated with detonation, allowing the PCM to retard ignition timing to prevent engine damage. Wit...
The most common cause of P0325 (Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)) is: Failed knock sensor with no piezoelectric output
Typical repair costs for P0325 range from $100 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive, but the PCM will retard ignition timing as a protective measure, reducing engine power and fuel economy. Avoid heavy loads, towing, or aggressive driving until repaired, as undetected knock during these conditions could damage the engine. Use premium fuel as a precaution until the sensor is replaced.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0325 to identify the root cause.
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Quick Info
Category
Powertrain
System
Ignition / Knock Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
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