U0238

Code

Generic U — Network/User

Lost Communication With Digital Audio Control Module D

Brand: Generic

Type: U — Network/User

Views: UK: 28 EN: 86 RU: 35

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Digital Audio Control Module D failure (hardware or firmware)
Loss of module power or ground (blown fuse, open circuit, poor ground)
Open, short, or high-resistance wiring or connector fault on the network or to the module
Fault or short on the vehicle communication bus (CAN, LIN or other network)
Missing/misconfigured termination or wrong baud rate on the bus
Aftermarket audio equipment or recent repairs that disturbed the bus

Symptoms

Infotainment/audio functions inoperative or intermittent
Radio, media, or speaker control missing for one zone
Cluster or head unit shows 'service audio' or communication warnings
Related modules report network communication U-codes
Settings or features unavailable in the vehicle user interface

What to check

Retrieve all network DTCs with a capable scan tool; note any other U-codes
Verify module presence using the scanner (can the tool communicate with the module?)
Inspect audio module connector for corrosion, bent pins, water ingress
Check fuses and relays supplying power to the audio module
Measure module supply voltage and ground continuity at the module harness
Visually inspect wiring harness along routing for damage, chafing, or repair splice

Signal parameters

CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive). Dominant: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
Typical CAN bus termination: two 120 Ω resistors in parallel ≈ 60 Ω across CAN_H and CAN_L at rest
Common bus data rates include 500 kbps or 250 kbps (verify vehicle-specific rate)
Module should appear on bus with periodic message ID; absence of ID indicates loss of communication

Diagnostic algorithm

Verify DTC is current (not historical). Record freeze frame and related U-codes.
Use an OEM-capable scan tool to attempt communication with Digital Audio Control Module D. Note tool errors.
Inspect module connector and harness for damage, corrosion, or loose pins. Re-seat connector.
Check fuses/relays and measure module supply voltage and ground at the connector with key on/engine off.
If power/ground OK, observe CAN bus traffic with a scanner or scope at the module connector. Confirm expected idle voltages and presence of messages.
Measure CAN bus termination resistance across CAN_H and CAN_L (expect ~60 Ω).
If bus levels are abnormal, isolate sections to locate short/open (disconnect module and observe change).
Check for other modules reporting communication faults; a faulty node may hold the bus dominant — unplug suspicious nodes one at a time while monitoring bus.
Inspect for aftermarket audio or recent repairs that could have altered the bus wiring; correct any improper splices or taps.
If wiring and bus are good but module fails to respond, consider module replacement or reflash/reprogram according to manufacturer procedure. Re-run diagnostics and road-test to confirm.
After repair, clear codes and verify the fault does not return. Document any modules reprogrammed or replaced.

Likely causes

Blown fuse or relay feeding the audio module
Disconnected or corroded connector at the audio module
Short to battery or ground on CAN_H or CAN_L wiring
Failed audio control module electronics
Network bus shorted, open, or missing termination resistor
Another module holding the bus dominant (faulty node)

Fault status

⚠️ Status

Lost Communication With Digital Audio Control Module D — indicates the vehicle network cannot receive valid messages from the module. Inspect power, ground, connector, wiring, and network integrity before replacing the module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours