Faulty knock sensor, internally failed or giving no signal; Damaged, chafed or corroded wiring to the sensor, including a short to ground; Poor connection at the sensor plug or ECU connector, such as corrosion, water ingress or a loose terminal; Incorrect sensor torque or poor contact with the block, giving a weak signal on some designs; Oil, coolant or heat damage to the harness near the engine, especially under the intake manifold on some engines; Fault inside the engine control unit knock input circuit.

P0327

Knock/Combustion Vibration Sensor A Circuit Low.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
27: FaultThe specific fault in that area

What it means

P0327 means the engine control unit has seen the signal voltage from knock sensor A (usually bank 1, or the only sensor fitted) fall below the expected range. The knock sensor produces a small voltage in response to engine vibration, so a very low or absent signal suggests a short to ground, an open circuit or a failed sensor. The ECU may retard ignition timing as a precaution because it can no longer detect knock reliably.

Symptoms

Engine warning light on
Reduced power or sluggish acceleration
Poorer fuel economy
Pinking or knocking under load, especially on poor fuel
Rough running or hesitation in some cases
Car may feel flat when the ECU falls back to a safe ignition map

Possible causes

Faulty knock sensor, internally failed or giving no signallikely
Damaged, chafed or corroded wiring to the sensor, including a short to groundlikely
Poor connection at the sensor plug or ECU connector, such as corrosion, water ingress or a loose terminallikely
Incorrect sensor torque or poor contact with the block, giving a weak signal on some designspossible
Oil, coolant or heat damage to the harness near the engine, especially under the intake manifold on some enginespossible
Fault inside the engine control unit knock input circuitrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including engine temperature, load and rpm when the fault set
Check for related codes such as other knock sensor, misfire or ignition faults, and check for any relevant technical service information for the model
Visually inspect the knock sensor wiring and connector for chafing, melted insulation, oil contamination, water and corrosion
Check the sensor mounting is secure and torqued to the manufacturer specification, with the sensor seated flat on a clean surface
With the ignition off, check the sensor circuit for continuity, short to ground and resistance against the manufacturer data, as the correct values depend on the model and engine
Check the reference or signal voltage at the ECU connector against the wiring diagram for the vehicle
Use live data to see whether the knock sensor signal responds when the engine block is tapped lightly near the sensor, if the model allows
Clear the code and road test to confirm whether it returns

How to fix

Repair or replace damaged wiring, and secure the harness away from heat and moving parts
Clean or replace the corroded or damaged connector or terminals
Replace the faulty knock sensor, fitting it with the correct torque and a matching part for the engine
Refit a loose sensor correctly, ensuring the mating surface is clean
Replace or repair the engine control unit only after wiring and sensor faults have been ruled out, following manufacturer procedure

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but the ECU may be running reduced ignition timing and the engine is not protected against knock. Avoid heavy loads and hard acceleration, use good quality fuel and get it checked soon to avoid possible engine damage.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.