U3524 indicates that the high‑voltage system interlock circuit F is detecting a voltage higher than expected. The interlock circuit is a safety loop that monitors the integrity of high‑voltage components; an abnormal high voltage reading suggests a fault in the wiring, connector, or interlock sensor itself.
The most common cause is chafed, pinched, or corroded wiring or a faulty connector in the interlock circuit F, which can cause a voltage pull‑up or short to high voltage.
The interlock switch or sensor that monitors circuit F may be stuck closed or internally shorted, producing an abnormally high voltage signal to the controller.
A malfunction within the battery‑pack interlock monitoring module can incorrectly report high voltage on circuit F even when the wiring is sound.
Less frequent, but a fault inside the high‑voltage battery management or body control module can misinterpret the interlock signal as high.
The powertrain control module could incorrectly log U3524 if it receives corrupt data, but this is uncommon; replacing the PCM is rarely needed for this code.
No. The PCM is rarely the cause of this code; most U3524 cases stem from wiring, connectors, or the interlock switch/sensor. Replacing the PCM should only be considered after those components have been verified good.
Driving may be possible in reduced‑power or limp‑home mode, but the high‑voltage interlock safety function is compromised. Continued operation risks loss of EV functionality or unexpected shutdown, so repair is recommended promptly.
Clearing the code only removes the warning; if the underlying fault remains, the code will return. Proper diagnosis and repair are required to prevent recurrence.