U0191 – Lost Communication With Audio/Video Control Module “B”

System: Network | Standard: ISO/SAE Controlled | Fault type: General | Location: Designator B

Definition source: SAE J2012/J2012DA (industry standard)

DTC U0191 indicates the vehicle network has detected a loss of communication with the Audio/Video Control Module “B”. In practical terms, one or more control modules expected to exchange messages with that module, but the messages were not received within the required timeframe. The exact detection logic, the modules involved, and which features are affected can vary by vehicle, so confirm module locations, network topology, and diagnostic procedures in the appropriate service information. This is a network communication fault, not proof that the audio/video module itself has failed; wiring, connectors, power/ground feeds, or the network itself can interrupt communications and trigger the code.

What Does U0191 Mean?

U0191 means “Lost Communication With Audio/Video Control Module ‘B’.” Under SAE J2012 DTC conventions, a U-code is a network-related fault, and this particular entry is set when the vehicle’s communication network indicates that the Audio/Video Control Module “B” is no longer communicating as expected. The code reflects a communication loss condition detected by one or more modules on the network (or by a central gateway, depending on design). Because “Module ‘B’” designation and message expectations vary by vehicle, always verify which physical module corresponds to “B,” what network it resides on, and which modules are reporting the loss.

Quick Reference

• Subsystem: Vehicle communication network (data bus) involving the Audio/Video Control Module “B”.
• Common triggers: Module offline, network open/short, high resistance at terminals, poor connector fit, or module power/ground interruption.
• Likely root-cause buckets: Wiring/connector issues; network integrity problems; power/ground feed faults to the module; module internal fault; configuration/software issues (varies by vehicle).
• Severity: Typically comfort/infotainment feature loss; may be moderate if the module participates in shared network functions (varies by vehicle).
• First checks: Verify other U-codes, check module power/grounds and connector condition, inspect network wiring near the module, confirm the module is present on the scan tool network list.
• Common mistakes: Replacing the module before verifying power/ground, condemning the entire network without checking localized connector/terminal problems, or ignoring related communication codes that point to the true segment/gateway issue.

Theory of Operation

Modern vehicles use one or more data networks to allow modules to share information. The Audio/Video Control Module “B” typically transmits and receives periodic messages and responds to requests from other modules. Those messages may support audio/video functions, human-machine interface coordination, and status reporting. Depending on vehicle design, communications may travel on a direct bus segment or through a gateway module that routes messages between networks.

A “lost communication” DTC is set when expected messages from the module are not received within a calibrated time window, or when the network reports the module as non-responsive. This can occur if the module loses battery feed or ground, if the network wiring is open/shorted, if terminals have poor contact or corrosion, or if the module is present but unable to transmit/receive due to an internal fault.

Symptoms

• No audio/video: Sound, video, or related infotainment features may be unavailable or intermittent.
• Blank display: Screen remains dark, frozen, or repeatedly reboots depending on system layout.
• Control loss: Steering-wheel, console, or touchscreen controls may not respond for audio/video functions.
• Network warnings: Additional communication-related DTCs may be stored in multiple modules.
• Intermittent operation: Functions may return temporarily after key cycles, bumps, or temperature changes.
• Battery drain: In some designs, a module that fails to sleep correctly after communication faults can contribute to parasitic draw (varies by vehicle).

Common Causes

• Open, shorted, or high-resistance wiring in the network communication circuits between modules
• Loose, corroded, backed-out, damaged, or contaminated connectors at the Audio/Video Control Module “B” or at network junction points
• Poor pin fit (spread terminals) causing intermittent contact under vibration or temperature change
• Power feed problem to the Audio/Video Control Module “B” (blown fuse, faulty relay, open in the feed circuit)
• Ground circuit issue for the Audio/Video Control Module “B” (open ground, high resistance at ground point)
• Network bus fault affecting multiple modules (short between network lines, short to power/ground, or a failed node loading the bus)
• Module internal fault in the Audio/Video Control Module “B” (hardware failure or internal communication fault)
• Configuration or software-related issue after module replacement, battery events, or network changes (varies by vehicle)

Diagnosis Steps

Tools helpful for diagnosing U0191 include a scan tool with full-network module access, wiring diagrams and connector views from service information, a digital multimeter for voltage-drop and continuity checks, and basic back-probing tools. A breakout lead set can reduce terminal damage risk. If available, a data logging function for network-related PIDs can help capture intermittent dropouts during a road test.

1. Confirm the code and capture freeze-frame/context data. Scan all modules, record U0191 and any related network, power supply, or ignition feed DTCs, and note whether the Audio/Video Control Module “B” is present in the module list. If multiple “lost communication” codes exist, treat it as a network-wide issue first.
2. Check whether the module can be contacted. Attempt to enter the Audio/Video Control Module “B” with the scan tool. If it is unreachable, proceed with power/ground and network checks. If it is reachable, treat U0191 as intermittent or historical and focus on connection integrity and conditions that reproduce the fault.
3. Verify the customer complaint and related functions. Confirm any audio/video feature loss, control head behavior, or warning messages that coincide with the stored DTC. Correlate the symptom timing with key cycles, bumps/vibration, or recent electrical work (varies by vehicle).
4. Prioritize basic electrical checks before network diagnostics. Inspect and test all fuses and relays that supply the Audio/Video Control Module “B,” including any feeds shared with other infotainment/network components. Do not rely on visual inspection alone; verify power is present where it should be with the circuit loaded.
5. Inspect connectors and harness routing. Key off and follow service information to locate the module and its connectors. Look for loose latches, pushed-out terminals, corrosion, moisture signs, insulation damage, pinch points, and prior repair splices. Correct any obvious issues before deeper testing.
6. Perform voltage-drop testing on power and ground circuits. With the system powered (conditions vary by vehicle), test for excessive voltage drop on the module’s power feed(s) and ground return(s) while the circuit is loaded. A poor power or ground can mimic a network failure by causing the module to reset or go offline intermittently.
7. Check network circuit integrity to the module. Using the wiring diagram, identify the network communication circuits at the Audio/Video Control Module “B.” With key off and the system in a safe state per service information, test for opens and shorts between the communication lines and to power/ground. If a short or open is found, isolate the section by disconnecting intermediate connectors/junctions as applicable (varies by vehicle architecture).
8. Use a controlled wiggle test to reproduce the fault. While monitoring the scan tool’s module list and relevant network status PIDs, gently flex the harness near the module, at connector backshells, and at known bend points. If communication drops in response to movement, focus on that segment for poor pin fit, broken conductors inside insulation, or connector damage.
9. Assess whether the issue is localized or network-wide. If other modules intermittently drop offline or multiple communication DTCs set together, suspect a shared network problem, a failing node loading the bus, or a shared power/ground issue. If only the Audio/Video Control Module “B” drops, keep the focus on its power, ground, connector, and network branch.
10. Log live data during a road test (if safe and relevant). If the problem is intermittent, use scan tool logging to capture the moment communication is lost. Note vehicle conditions when it occurs. Use the results to guide inspection to vibration/heat-affected areas, shared grounds, or areas that recently had repairs.
11. Confirm the repair and verify no secondary issues. After repairs, clear DTCs and perform a verification drive cycle appropriate to the vehicle. Re-scan all modules to ensure U0191 does not return and that no new network or power supply codes were introduced. Recheck that all related audio/video functions operate normally.

Professional tip: If the Audio/Video Control Module “B” is intermittently missing from the scan tool’s module list, treat that observation as a strong clue of a power/ground dropout or a connector/terminal contact issue. Before suspecting the module itself, prove stable power and ground under load with voltage-drop testing and use a wiggle test while watching module presence and communication status in live data.

Possible Fixes & Repair Costs

Repair cost for U0191 varies widely because the “lost communication” condition can be caused by anything from a simple connector issue to a power/ground fault or a module-level problem. Diagnosis time, parts availability, and vehicle-specific network layout all affect the final total.

• Clean, reseat, and properly secure connectors at the Audio/Video Control Module “B” and any in-line connectors in its network path; correct pin fit issues found during inspection.
• Repair or replace damaged wiring in the communication circuits (for example, chafed, pinched, stretched, or corroded conductors) and restore proper shielding/routing where applicable.
• Restore module power and ground integrity by repairing opens/high resistance at fuses, splices, grounds, or power feeds; verify with voltage-drop testing after the repair.
• Address water intrusion or corrosion at connectors or junction points by repairing the source of intrusion and replacing terminals/connectors as needed.
• Perform a network-level repair if another module or network junction is bringing the bus down (varies by vehicle); verify by isolating segments and confirming communication returns.
• If testing proves the Audio/Video Control Module “B” is not communicating despite correct power/ground and network integrity, replace the module and carry out any required setup/programming per service information.

Can I Still Drive With U0191?

In many vehicles, U0191 mainly affects infotainment-related functions (audio/video features) and may not change basic driveability; however, network faults can be unpredictable and may coincide with other warnings or multiple communication codes. If you also have stalling, no-start, reduced power, brake/steering warnings, or a rapidly expanding list of U-codes, do not drive until the network/power issue is diagnosed. If the vehicle drives normally, keep trips short, avoid distractions from inoperative displays, and schedule diagnosis soon.

What Happens If You Ignore U0191?

Ignoring U0191 can lead to persistent or worsening loss of audio/video functions, intermittent module resets, and repeated warning messages as the vehicle continues to detect missing network messages from Audio/Video Control Module “B.” If the root cause is corrosion, a loose connection, or a power/ground problem, the condition may spread to additional circuits or modules over time, making diagnosis more difficult and increasing the chance of broader network communication issues.

Last updated: March 17, 2026

Vehicles Commonly Affected by U0191

• Vehicles with multiple infotainment control modules and separate audio/video controllers
• Vehicles using a shared in-vehicle network for infotainment and body functions
• Vehicles with rear-seat entertainment or secondary display/controller modules
• Vehicles with amplifier, display, and media modules distributed across the cabin
• Vehicles with optional audio/video packages that add extra network nodes
• Vehicles with modules located in moisture-prone areas (doors, cargo areas, under-seat locations) depending on design
• Vehicles that have had recent accessory installation or wiring repairs affecting interior harness routing
• Vehicles with prior low-voltage events or battery service that may expose weak connections

After any repair, confirm the fix by verifying stable communication with Audio/Video Control Module “B,” ensuring related functions operate normally, and performing a final scan to confirm U0191 does not return during an appropriate road test or functional check.