Damaged or chafed knock sensor 4 signal wire shorted to voltage or to a nearby harness; Corroded, loose, or pushed-back terminal at the knock sensor 4 connector or at the engine control module plug; Failed knock sensor 4, typically from heat, age, or impact damage to its housing; Open or high-resistance ground path at the sensor mounting boss due to rust, paint, or debris; Internal fault in the engine control module's knock sensor input circuit; Harness damage from rodent chewing, heat brittleness, or previous engine work pinching the loom

DTC codes / Volkswagen codes / P1324

P1324 · VolkswagenKnock Sensor 4 Circuit High Input

Q: What does code P1324 mean?

Knock Sensor 4 Circuit High Input. P1324 on a Volkswagen means the engine control module has detected an abnormally high voltage on the signal circuit for knock sensor number four, which is one of the sensors that listens for detonation in the engine block. The circuit is being pulled toward the sensor's reference voltage instead of showing the small fluctuating signal a healthy sensor produces, so the computer flags the input as out of range.

P1324 on a Volkswagen means the engine control module has detected an abnormally high voltage on the signal circuit for knock sensor number four, which is one of the sensors that listens for detonation in the engine block. The circuit is being pulled toward the sensor's reference voltage instead of showing the small fluctuating signal a healthy sensor produces, so the computer flags the input as out of range.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other symptoms the driver can feel
Reduced engine performance or a soft limp mode because the computer retards ignition timing to protect the engine
Noticeable loss of power and sluggish acceleration under load, especially when climbing or towing
Poor fuel economy as the computer runs a conservative timing strategy
In rare cases, audible pinging or knocking from the engine if timing retard is insufficient

Common causes, most likely first

Damaged or chafed knock sensor 4 signal wire shorted to voltage or to a nearby harness
Corroded, loose, or pushed-back terminal at the knock sensor 4 connector or at the engine control module plug
Failed knock sensor 4, typically from heat, age, or impact damage to its housing
Open or high-resistance ground path at the sensor mounting boss due to rust, paint, or debris
Internal fault in the engine control module's knock sensor input circuit
Harness damage from rodent chewing, heat brittleness, or previous engine work pinching the loom

How to diagnose and fix it

Scan all modules and record freeze-frame data for P1324, then visually inspect knock sensor 4 and its harness for obvious damage
Disconnect the sensor and check the signal circuit for a short to voltage with a digital multimeter, wiggle-testing the loom while watching the reading
Measure resistance across knock sensor 4 and compare it to the known-good value for the engine, replacing the sensor if it is out of spec
Clean the sensor mounting boss and block surface to bare metal and torque the sensor to specification to restore a proper ground
Back-probe the signal circuit at the engine control module and confirm the voltage is within the expected range with the sensor connected
Repair or replace the affected section of harness and re-secure it away from hot or moving components
Clear the fault, run a road test under load, and verify the code does not return before releasing the vehicle

Why knock sensor 4 keeps coming back

A high-input code on a knock sensor is frequently a wiring problem rather than a failed sensor, so replacing the sensor first often leaves the code unchanged.
Knock sensor 4 is often the hardest one to reach on VW engines, and technicians sometimes damage its connector or leave the mounting surface contaminated during access, which sets the code again.
The engine control module compares knock sensor signals across all cylinders, so a single high-input fault can cause global timing retard and a power loss that feels like a much larger problem.
Aftermarket sensors and incorrect torque on the mounting bolt can produce a signal the module reads as high input, so genuine parts and the specified torque matter here.
A poor engine ground or a failing battery can create voltage offsets that mimic a high knock sensor signal, so check charging and ground integrity before condemning the module.

Can I keep driving with P1324?

You can usually drive the vehicle to a workshop, but avoid heavy throttle, towing, and sustained high-load driving because the computer may not be protecting the engine with correct knock control. If the check engine light is flashing or you hear audible pinging, stop driving and have it diagnosed immediately.

Tools that help

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Guidance is general and written for Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.