Faulty knock sensor (40% likelihood): The knock sensor has failed internally and is outputting a voltage signal below the ECM's minimum threshold, indicating a low-output failure mode. Corroded or damaged wiring (30% likelihood): Corrosion, fraying, or a poor ground connection in the knock sensor wiring harness is causing excessive resistance and a low voltage reading at the ECM. Loose or poorly mounted sensor (15% likelihood): The knock sensor is not making firm contact with the engine block due to improper torque or a damaged mounting bolt, reducing signal strength. Poor ground connection (10% likelihood): A bad ground at the sensor or ECM is preventing the full signal voltage from reaching the control module. ECM fault (5% likelihood): The engine control module's internal circuits for reading the knock sensor signal may have degraded, interpreting a normal signal as low.

How much does it cost to fix P0327?

DIY repair typically costs $20–$80 for parts. Professional repair runs $150–$400 including parts and labor.

P0327

Powertrain

Low

Knock Sensor 1 Circuit Low Input (Bank 1 or Single Sensor)

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The P0327 code means the Engine Control Module is receiving a voltage signal from Knock Sensor 1 (Bank 1) that is below the expected minimum threshold. Knock sensors produce very small voltage signals (often millivolts) when they detect engine vibration, so even minor issues with connections or mounting can push the signal below what the ECM considers valid.

The most frequent cause is a failed knock sensor, but wiring problems are a close second. Because knock sensor signals are so low-voltage, even slight corrosion on a connector pin or a small amount of resistance in the wiring can drop the signal below threshold. Rodent damage to wiring is also a surprisingly common cause of this code.

While this code won't leave you stranded, the ECM will retard ignition timing as a precaution, which reduces your engine's power and fuel efficiency. You can safely drive to a shop, but plan to have it diagnosed within a few weeks. The repair is usually straightforward — replacing the sensor and inspecting the wiring. On vehicles where the sensor is accessible on the side of the block, it's a reasonable DIY job. On engines where it's buried under the intake manifold, the labor cost increases significantly.

Severity

Low — MonitorThis Month

Symptoms

•Check Engine light is on
•Reduced engine power during acceleration
•Slight pinging or knocking noise from the engine
•Decreased fuel efficiency
•Engine feels sluggish or hesitant under load

Likely Causes

Faulty knock sensor40%

The knock sensor has failed internally and is outputting a voltage signal below the ECM's minimum threshold, indicating a low-output failure mode.

Corroded or damaged wiring30%

Corrosion, fraying, or a poor ground connection in the knock sensor wiring harness is causing excessive resistance and a low voltage reading at the ECM.

Loose or poorly mounted sensor15%

The knock sensor is not making firm contact with the engine block due to improper torque or a damaged mounting bolt, reducing signal strength.

Poor ground connection10%

A bad ground at the sensor or ECM is preventing the full signal voltage from reaching the control module.

ECM fault5%

The engine control module's internal circuits for reading the knock sensor signal may have degraded, interpreting a normal signal as low.