U0187 — Data bus: digital disc player/changer module A – no communication #

Note: The wording of this Diagnostic Trouble Code (DTC) may vary depending on the vehicle manufacturer (OEM). Always refer to your vehicle’s specific service information.

• “Lost Communication With Digital Disc Player/Changer A” (GM, Ford, Chrysler)
• “No Communication With DVD/CD Changer Module” (Toyota, Lexus)
• “Multimedia Player Module A Communication Fault” (Mercedes-Benz)
• “Disc Changer Module A Not Responding on CAN Bus” (Volkswagen/Audi)

Summary for DTC U0187 #

The U0187 code indicates that the vehicle’s main computer (often called the Powertrain Control Module or PCM) has lost communication with the digital disc player/changer module A via the CAN bus (Controller Area Network bus), which is a communication system connecting electronic modules in modern vehicles. In everyday terms, this means your car’s computer can’t “talk” to the CD, DVD, or multimedia changer module. This issue doesn’t usually affect critical drivability, but it can impact access to entertainment features and, in some cases, other dependent systems. The code is most often stored when a communication interruption or failure is detected multiple times within a short period. A U0187 is typically related to wiring, module faults, or network integrity problems rather than a mechanical failure.

Common Symptoms for U0187 #

When the U0187 code is present, you may notice symptoms tied to your vehicle’s entertainment or multimedia system operation. In some cases, there may be no obvious outward sign, especially if you rarely use the disc changer. However, these are the most commonly reported symptoms:

• Disc changer, CD, or DVD player does not function or respond
• Entertainment system shows an error or “No Disc” message
• Loss of audio input or inability to select media from the changer
• Radio or infotainment system freezing or rebooting
• Warning lights for multimedia or communication systems
• No communication with the disc module during diagnostic scan

Probable Causes for U0187 (Ranked by Frequency) #

Several potential issues can trigger a U0187 code, but some are more common than others. Here’s what technicians typically find, in order of likelihood:

1. Loose, corroded, or damaged wiring/connectors at the disc player/changer module or along the CAN bus
2. Faulty or failed disc player/changer module A itself
3. CAN bus wiring issues (short to ground, short to power, or open circuit)
4. Aftermarket radio or entertainment system installation interfering with OEM (Original Equipment Manufacturer) communications
5. Software or firmware corruption in the changer or main control module
6. Faulty Body Control Module (BCM) or Gateway Module affecting network communication

Step-by-Step Diagnostic for U0187 #

Diagnosing a U0187 code requires a systematic approach to isolate the source of the communication failure. Here’s a proven step-by-step process:

• 1. Verify the code and symptoms: Use a professional OBD-II scanner to confirm the U0187 code is present and check for other related codes.
• 2. Inspect visible wiring and connectors: Look for signs of damage, loose connections, corrosion, or water intrusion at the disc changer module and along the related wiring harness.
• 3. Check the CAN bus network integrity: Using a multimeter or oscilloscope, verify voltage and continuity of CAN High and CAN Low circuits at the module connector.
• 4. Attempt module communication: With a scan tool, try to establish direct communication with the disc player/changer module. If unavailable, the module may be offline or faulty.
• 5. Test power and ground: Ensure the module is receiving proper battery voltage and has a good ground connection.
• 6. Disconnect aftermarket equipment: If present, temporarily remove or disconnect any non-OEM audio or multimedia devices to rule out interference.
• 7. Substitute known-good module (if possible): Swap in a compatible, functioning disc changer module to see if communication is restored.
• 8. Consult OEM wiring diagrams: Trace wiring for possible faults specific to your vehicle make/model.

Possible Repairs for U0187 #

After identifying the root cause, these are the most common and effective repair actions for a U0187 code:

• Repair or replace damaged wiring/connectors at the module or along the CAN bus circuit
• Replace the faulty disc player/changer module A
• Restore CAN bus wiring integrity (repair open, shorted, or corroded circuits)
• Remove or properly integrate aftermarket devices to ensure OEM network compatibility
• Update or reprogram module software/firmware as recommended by the OEM
• Replace or reprogram the Body Control Module (BCM) or Gateway Module if found defective

Is It Safe to Drive With U0187? #

Yes, in most cases, you can continue driving with the U0187 code present. This fault does not affect critical engine or braking functions, as it is limited to the multimedia/disc changer system. However, you may lose access to certain entertainment features, and in rare cases, the infotainment system may act unpredictably. If you notice additional warning lights or experience problems with other vehicle systems, have the car inspected promptly.

Vehicles Most Commonly Affected by U0187 #

The U0187 code is most frequently encountered in vehicles equipped with multi-disc CD, DVD, or multimedia changers, especially those produced from the mid-2000s to the early 2010s. Here are some brands and models where this code appears more commonly:

• General Motors (Chevrolet, GMC, Cadillac, Buick) — models with rear-seat entertainment or multi-disc changers
• Ford/Lincoln — vehicles with factory-installed DVD players or premium sound systems
• Toyota/Lexus — models featuring Mark Levinson or other premium audio systems
• Mercedes-Benz — E-Class, S-Class, and SUVs with COMAND multimedia
• Volkswagen/Audi — models with MMI or RNS systems and disc changers

Common Mistakes & Best Practices for U0187 #

When addressing a U0187 code, certain oversights can lead to wasted time or repeat failures. Here are some common mistakes and best practices:

• Replacing the disc changer module without inspecting wiring or connectors
• Ignoring aftermarket device interference — always check for non-OEM installations
• Overlooking intermittent faults caused by vibration, temperature, or movement
• Neglecting to check module power and ground before suspecting a communication issue
• Best Practice: Always clear codes after repairs and retest for communication with the module before returning the vehicle to service

Quick FAQ for U0187 #

Still have questions? Here are answers to the most common quick queries:

• Q: Can a blown fuse cause U0187?
  A: Yes, if the fuse supplying power to the disc changer module is blown, it can prevent communication and trigger the U0187 code. Always check fuses as part of your diagnosis.
• Q: My radio works, but the disc changer doesn’t. Is this related?
  A: Yes, the radio and disc changer are separate modules. The radio may still function normally even if the disc changer module is offline due to a U0187 fault.
• Q: Will disconnecting the battery clear this code?
  A: Disconnecting the battery may temporarily clear the code, but if the underlying problem persists, the U0187 code will return shortly after the system performs another self-check.