What does code P1504 mean?

Q: What does code P1504 mean?

Intake Air System Bypass Leak Detected. P1504 on Volkswagen vehicles indicates that the engine control module has detected an air leak in the intake air system bypass circuit, typically involving the secondary air injection system or the intake manifold tuning valve. The computer monitors the bypass valve's expected response and flags a leak when the actual airflow or pressure change does not match the commanded state.

DTC codes / Volkswagen codes / P1504

P1504 · VolkswagenIntake Air System Bypass Leak Detected

P1504 on Volkswagen vehicles indicates that the engine control module has detected an air leak in the intake air system bypass circuit, typically involving the secondary air injection system or the intake manifold tuning valve. The computer monitors the bypass valve's expected response and flags a leak when the actual airflow or pressure change does not match the commanded state.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

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