This code indicates that the vehicle’s communication network has lost data transmission with the factory CD or DVD changer module. The module is not responding to polling messages from the audio head unit or network gateway, effectively disappearing from the data bus. This typically disables disc playback functions while leaving other vehicle systems unaffected.
The most common cause is a failed internal power supply or communication circuit within the changer unit itself, often caused by age, mechanical jam, or electrical overload that prevents the module from booting up to communicate.
Breaks, chafing, or short circuits in the power, ground, or communication lines leading to the changer (often routed through the trunk, rear console, or hatch areas) interrupt the electrical signals required for bus communication.
Moisture intrusion, spilled liquids, or physical wear can corrode pins or loosen terminals at the module’s harness connector or intermediate junctions, causing intermittent or permanent loss of contact.
A short-to-voltage, short-to-ground, or open in the specific branch of the CAN or media bus wiring that serves only the disc changer can isolate this module while other network devices continue to function.
Previous aftermarket audio or video installations may have damaged the original harness, spliced into the wrong circuits, or removed the factory module without properly terminating the communication bus.
Rarely, the master controller responsible for relaying messages between the disc changer and the rest of the network may fail to pass data, though this usually produces multiple communication codes, not just U0187.
No. The PCM is almost never the cause of this code. U0187 relates specifically to the entertainment system’s disc changer, and the fault lies almost always with the changer module itself, its wiring, or the audio system gateway—not the powertrain control module.
Yes. This code affects only the CD or DVD player functionality and has no impact on engine performance, transmission operation, emissions, or safety systems. You can drive the vehicle normally while planning repairs.
Low voltage or voltage spikes during battery disconnection and reconnection can cause communication modules to lose synchronization. If the code appeared immediately after battery service, clear it and monitor; if it returns, the disc changer likely has a pre-existing internal fault that was revealed by the power interruption.
Disconnecting the battery will erase the code temporarily, but if the underlying communication failure persists—such as a dead changer module or broken wire—the code will return after the system completes its initialization and communication verification tests.