U0187 Low Generic / SAE

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

Network and Communication Lost Communication

What to do

You may never have used the CD player, and this may still be worth fixing. Here is why.

The disc player is on the same network as everything else in the car. A module that has failed can stop the car agreeing to switch itself off after you lock it — and a car that never fully sleeps flattens its battery in three or four days. So a device nobody uses can still leave you unable to start the car, which is the reason not to ignore it.

Two free checks first.

Is there a disc stuck in it? A jammed disc leaves the mechanism reporting something the rest of the car cannot make sense of, and it is a common cause with no electrical fault at all.

And has the battery been going flat over a few days? If so, this is worth doing now rather than eventually.

If the changer is in the boot, look for water — a hardened rear light seal or an aged tailgate seal puts water right where it lives. If the player is in the dashboard and the radio has stopped too, the fault is more likely the stereo itself.

And if you genuinely never use it, ask whether it can simply be disconnected and the car told to stop expecting it. That is a legitimate answer — but it must be coded out properly rather than just unplugged, or the car complains about the missing module instead.

What this code means

The disc player module has stopped being heard from. The general reasoning is at U0100, and U0488 makes the case for fixing a device nobody uses.

That case is stronger for silence than for bad data, and it is worth restating precisely. A module that has failed in a way that leaves it drawing current, or one whose absence stops the network agreeing to sleep, keeps the vehicle awake after it is locked — and a battery flat in three or four days is the result. So a device that has not been used in years can still leave somebody unable to start their car.

Two free checks come before anything is opened.

Is there a disc stuck in it? A jammed mechanism reports a state the head unit cannot resolve, and it is a genuinely common version of this with no electrical fault at all.

And has the battery been going flat? That answer decides whether this is a nuisance or the thing to fix this week.

Where it lives decides the cause, as with the amplifier at U0186. A boot-mounted changer sits in the side panel where water arrives through a rear light gasket or a tailgate seal, and where a shifting load can strike it. A dash-mounted player shares the head unit's supply, so if the radio has gone too, U0184 is the better page.

And the honest option stands: where the vehicle allows it, disconnecting a redundant player is a legitimate outcome — provided it is coded out properly so the vehicle stops expecting it, rather than simply unplugged.

Likely causes

Start here

Less common

Module not coded to the vehicle · specialist
Another module holding the bus down · specialist
Damaged wiring harness · moderate

Symptoms

Components involved

Information, not instruction

CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.

Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.

Community experience

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The car — make, model, year and engine. The same fault behaves differently on each.
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