What does it mean?
U1004 is a Network (CAN bus, module communications) fault code. It indicates: DIS AMP Unit Temperature Sensor Signal Error in Tunner and Amplifier .
Symptoms
- Sound fades or mutes after long periods of loud playback and returns when the system cools
- Amplifier or sound system warning message on the display
- Volume automatically limited by the system
- Distorted output before the system mutes
- Amplifier housing noticeably hot to the touch
- Fault stored together with other audio network codes
Likely causes
- Failed internal temperature sensor or a broken solder joint on the amplifier board
- Amplifier genuinely running hot because it is mounted in a sealed or padded location
- Blocked cooling vents, or dust and carpet fibres packed into the heatsink fins
- Continuous high volume operation into a low impedance or partly shorted speaker load
- Supply voltage too low or too high, which raises internal dissipation
- Water damage from a boot leak or spare wheel well moisture, common where amplifiers are mounted
- Amplifier software fault after coding or module replacement
How to fix it
- Reproduce the fault by running the system at high volume and noting whether it mutes only when hot
- Find the amplifier, usually in the boot or under a seat, and check its mounting for blocked airflow and trapped insulation
- Clean dust, carpet fibres and debris from the heatsink and vents
- Read the amplifier temperature value in live data and compare it with the ambient and with the second sensor if fitted
- Measure the supply voltage and do a voltage drop test on the amplifier feed and ground during loud playback
- Test the speaker circuits for a short or a low impedance load that would drive the amplifier into overheating
- Check the amplifier area for water ingress, especially near the spare wheel well, and dry or reseal as needed
- Reprogram or replace the tuner and amplifier unit only after cooling, supply and speaker load have been proven correct