What does it mean?
U2003 is a Network (CAN bus, module communications) fault code. It indicates: Manufacturer-Specific CAN/Network Bus Fault . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms
- Disc functions unavailable; the display shows an error or reports no changer fitted
- A disc will not load or will not eject
- The audio system reboots whenever disc mode is selected
- Radio and other audio sources still work normally
- Clicking or motor noise from the changer without any playback
- Scan tool cannot reach the disc unit
Likely causes
- Power feed or fuse to the disc changer lost
- Connector at the changer loose or corroded, typically in the glovebox, under a seat or in the boot
- Damaged bus wiring between the head unit and the changer
- Changer mechanically jammed by a stuck disc, so its processor locks up and stops answering
- Poor ground at the changer mounting bracket
- Changer removed or replaced without the head unit being configured for it
- Internal failure of the changer, which becomes more likely with age and heat
How to fix it
- Check the fuse and measure supply voltage and ground at the changer connector
- Reseat the connector and inspect it for corrosion and bent pins
- Verify bus continuity between the head unit and the changer
- Disconnect the changer temporarily to see whether the rest of the audio system returns to normal
- Check whether a disc is jammed inside and follow the correct removal procedure for the unit
- Configure the head unit correctly if the changer has been removed or replaced
- Replace the changer only after power, ground and bus wiring have tested good