What does code P1321 mean?

Q: What does code P1321 mean?

Knock Sensor 3 Circuit Low Input. P1321 on Volkswagen vehicles means the engine control module (ECM) has detected a low voltage signal on the circuit for knock sensor 3, which is typically the sensor monitoring the cylinder bank or engine block area furthest from the front. The ECM expects the sensor to return a small AC voltage that rises with engine knock, but instead it sees a signal that stays below the minimum threshold, so it flags the circuit as low input.

DTC codes / Volkswagen codes / P1321

P1321 · VolkswagenKnock Sensor 3 Circuit Low Input

P1321 on Volkswagen vehicles means the engine control module (ECM) has detected a low voltage signal on the circuit for knock sensor 3, which is typically the sensor monitoring the cylinder bank or engine block area furthest from the front. The ECM expects the sensor to return a small AC voltage that rises with engine knock, but instead it sees a signal that stays below the minimum threshold, so it flags the circuit as low input.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

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