DTC codes / Volkswagen codes / P1398
P1398 on Volkswagen vehicles means the engine control module has detected a short to ground on the circuit that carries the engine RPM signal, so the computer is not receiving a valid crankshaft speed input. The module sets this code when the signal wire is pulled to ground voltage instead of showing the expected pulsed or biased voltage.
Guidance is general and written for Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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