U0491 means a control module on the vehicle network received data from the digital disc player or changer that was corrupted, out of sequence, or did not match the expected protocol. The code specifically points to Module D as the source of the invalid message. This typically indicates a fault within the changer, its wiring, or the network link carrying that data.
The module's processor or network transceiver may be damaged, causing it to broadcast garbled or non-compliant data frames that the receiving module rejects.
Opens, shorts-to-power, shorts-to-ground, or corrosion in the communication lines can corrupt or interrupt the data stream between the changer and the rest of the system.
Voltage drop or a loose ground can cause the module to operate erratically and transmit invalid data even if the module itself is otherwise functional.
Corrupted or outdated internal software may cause the module to send messages in an unexpected format that the receiving module cannot validate.
Although less common, the module reading the data may incorrectly interpret valid messages due to an internal parsing or software fault.
Yes. This code relates to the media system and does not affect engine operation, braking, or steering.
No. U0491 is a body or infotainment network fault involving the disc changer. The engine computer is not part of this circuit, and replacing it will not resolve the code.
The fault is specific to the data stream from the disc changer module. Other sources, such as radio or streaming, operate independently and are unaffected.
It can. If the disc changer is transmitting data in an incorrect format due to outdated or corrupted firmware, a software update may restore proper communication without replacing hardware.