U0187–U0190 Lost Communication With Digital Disc Player/Changer Module A

Which code is which

Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.

The definition

U0187: Lost Communication With Digital Disc Player/Changer Module A.

U0187 is a network code (communication between control modules), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.

What to check first

Cheapest and fastest checks first:

1. Check power and earth at the module first - a module with no supply cannot answer.
2. Check the two data-bus wires for continuity and for a short between them.
3. Scan the other modules: if several report the same module missing, the fault is at that module rather than on the bus.

What actually causes this on a VAG

This is an infotainment fault, not an engine one. It means whichever unit is in charge of the audio system can no longer hear from the CD or media player module. On many VAG cars that unit is a separate changer in the glovebox or in a boot side panel. On better-equipped Audi and VW models the audio components are linked by a fibre-optic ring rather than by ordinary wiring, and on those the symptom is dramatic: one broken link takes the whole ring out, so the radio, amplifier and phone go quiet together rather than just the CD. Because this fault lives in the infotainment side of the car, a generic engine-only scan will not show it - it has to be read from the audio or radio module with a tool that talks to those units.

Most likely causes, in order

1. A leftover code from a flat battery, or from a unit that was removed. A discharged battery, a jump start or a car left standing throws a scatter of lost-communication codes across every module. Equally, if a CD changer was removed at some point, the head unit is still coded to expect it and will report it missing forever. Check first whether the car actually still has a player fitted, then clear the codes and see which ones genuinely come back.
2. Power or fuse to the player. If the unit gets no supply it cannot announce itself. Find its fuse and check whether the unit shows any sign of life at all. This is the cheapest real fault and it takes minutes.
3. A break in the fibre-optic ring. On cars with the optical audio ring, a bent, unseated or damaged fibre lead - or any single component on the ring that is faulty or stuck asleep - stops the ring communicating and takes the rest of the audio system with it. The tell-tale is the whole system being dead rather than just the CD source. These leads are easily crushed or left unclipped when trim is refitted, so recent interior or boot work is a strong clue.
4. Wiring or water damage at the unit itself. Boot-mounted units get knocked by luggage and are vulnerable to water from a tired boot seal or a leaking rear light seal. Pull the trim, check the connector is fully home and look for damp or corrosion before condemning the player.

Worth knowing: Before buying a replacement unit, have the head unit's coding checked against what is physically fitted. Plenty of these codes are nothing more than a car still expecting equipment that is no longer there, or the aftermath of a flat battery, and neither is fixed by new hardware.

Common questions

What does U0187 mean?

U0187 means Lost Communication With Digital Disc Player/Changer Module A. This module has stopped talking on the car's data network, so nothing else can hear it.

Can I drive with U0187?

The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.

Related reading

• Several warning lights on at once: usually one cause, not many
• Do you actually need a VAG-specific scan tool?
• Key not recognised or car won't unlock: VW and Audi
• Why the same fault code has completely different causes