P0325 — Knock Sensor 1 Circuit (Bank 1 or Single Sensor)
P0325 sets when the knock sensor signal is out of range or missing, preventing the ECM from detecting detonation. Knock sensors are torque-sensitive — always use a torque wrench on installation. Scope verification and proper torque prevent repeat failures.
Fault Overview
Failed knock sensor, open or shorted wiring, poor sensor mounting (torque critical), connector corrosion, and engine mechanical noise misinterpreted as a circuit fault are the primary causes. False codes can occur from actual engine knock caused by carbon or low-octane fuel.
Engine & Platform Coverage
Symptoms
- •P0325
- •knock sensor circuit
- •knock sensor code
- •detonation sensor fault
Possible Causes
- 1.Failed knock sensor
- 2.Open or shorted wiring
- 3.Poor sensor mounting (torque critical)
- 4.Connector corrosion
- 5.Actual engine knock from carbon or low-octane fuel
Wiring & Circuit Notes
Knock sensor connector and shielded wiring. Check for damage near the engine block.
DVOM Specs & Sensor Tests
Sensor resistance if specified. Signal activity with a scope while tapping the engine block. Proper mounting torque per OEM specification.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
4 steps locked behind Technician Mode- 1Step 1 — Inspect Connector and Wiring: Inspect the knock sensor connector and shielded wiring for damage or corrosion.
- 2Step 2 — Check Sensor Mounting and Torque: Check sensor mounting and torque. Knock sensors are torque-sensitive — over or under torque causes false codes.
- 3Step 3 — Measure Resistance if Applicable: Measure sensor resistance if specified by the OEM.
- 4Step 4 — Scope the Signal While Inducing Light Knock: Scope the signal while inducing light knock (or tapping the block near the sensor). A working sensor should produce a signal.
- 5Step 5 — Replace the Sensor if No Signal and Wiring Is Good: Replace the knock sensor if no signal is present and wiring and torque are proven good.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Typical Repair Costs
Replace knock sensor $50–200; repair wiring $50–200; correct mounting torque $0 (labor only).
Related Codes & Pages
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Summary
Use the AI Diesel Tech diagnostic engine to run this code through a structured, evidence-gated sequence and get a confirmed root cause before any parts are replaced.