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DTC codes / U04xx · Invalid data received from a module / U04AA
U04AA means the vehicle's main computer has lost the ability to receive valid data from the hybrid or electric vehicle battery interface control module, which is the electronic gateway that translates and relays critical battery status information. The computer detects this when the messages it expects from that module are missing, corrupted, or flagged as invalid on the controller area network (CAN) bus, so it cannot trust the battery data it needs for safe operation.
Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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