U3515 indicates a fault in the high‑voltage interlock loop circuit C, which monitors the safety connection between the vehicle’s high‑voltage battery and other components. The control module has detected an abnormal voltage or open/short condition in this circuit.
The high‑voltage interlock plug or its pins may not be making proper contact, causing an open or high‑resistance condition.
Chafed, cracked, or pinched wires in the interlock circuit can interrupt the signal.
A blown fuse will break the circuit and trigger the code.
A failed relay or the battery control module that manages the interlock can cause loss of circuit integrity.
The module that monitors the interlock may develop an internal fault.
A PCM issue can generate U3515, but this is uncommon and typically follows other component failures.
Clearing the code without fixing the underlying circuit issue may cause it to reappear after the vehicle runs a self‑check.
No, U3515 is related to the interlock loop, not the battery cells themselves, so battery replacement is rarely required.
The PCM is seldom the root cause; most often the fault lies in the wiring, connector, or a blown fuse.
The vehicle may limit power or display warnings, so it is best to address the issue before extended driving.