U0156 – Lost Communication With Navigation Display Module

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

Definition source: SAE J2012/J2012DA (industry standard)

DTC U0156 indicates a network communication problem where one or more control modules are no longer receiving expected messages from the Navigation Display Module. This is a communications integrity issue, not a direct statement that the display itself has failed. The vehicle’s network is designed to share data (status, commands, and confirmations) between modules; when those messages stop for longer than the allowed time, U0156 can set and features tied to the navigation display may be limited or unavailable. DTC behavior, affected features, and the exact monitor logic vary by vehicle, so always verify the network layout, connector views, and pinpoint tests using the correct service information.

What Does U0156 Mean?

U0156 – Lost Communication With Navigation Display Module means the vehicle’s network controller(s) detected that communication with the Navigation Display Module is missing or not valid. Under SAE J2012 DTC structure, this is a “U” (network) code describing a loss-of-communication condition rather than a sensor signal that is simply high, low, or out of range. In practice, at least one module expected periodic network messages from the Navigation Display Module and did not receive them within the calibrated time window. The root cause can be a power/ground issue at the module, a wiring/connector fault on the network circuits, or a network-level problem affecting multiple modules.

Quick Reference

• Subsystem: Vehicle network communications involving the Navigation Display Module (data bus and related power/ground feeds).
• Common triggers: Navigation Display Module offline, bus open/short, connector/pin issues, low system voltage, module reset, or network congestion/error state.
• Likely root-cause buckets: Wiring/connector faults, power/ground supply problems, network bus integrity issues, module internal fault, or configuration/software mismatch (varies by vehicle).
• Severity: Typically low to moderate; infotainment/navigation functions may be lost, but some vehicles integrate critical alerts into the display so safety impact can vary.
• First checks: Confirm which modules set U0156, check for battery/charging DTCs, verify the module powers up, and inspect network connectors and grounds.
• Common mistakes: Replacing the display/module without verifying power/ground and bus integrity, or ignoring other network DTCs that point to a broader communication fault.

Theory of Operation

The Navigation Display Module communicates with other modules over the vehicle network, sending and receiving messages such as device status, configuration, user interface commands, and data required to render information on the display. Other modules rely on these messages to confirm the display is present and responding, even if navigation features are not actively being used.

A module supervising network traffic monitors for the presence and validity of expected messages. If those messages stop, become consistently invalid, or the module is seen as non-responsive on the bus, the supervising module records a lost-communication fault and U0156 may set. Causes can include the Navigation Display Module losing its battery feed, ignition feed, or ground; an open or short on network wiring; connector pin fit/corrosion; or a network condition that prevents clean message exchange. Exact message timing and supervision rules vary by vehicle.

Symptoms

• Blank display: Screen remains dark, frozen, or continuously reboots.
• Navigation inoperative: Map, route guidance, or related functions unavailable or stuck loading.
• Loss of related features: Functions integrated into the display (menus, settings, prompts) may be missing or limited.
• Warning indicators: A warning message may appear elsewhere indicating infotainment or communication issues (varies by vehicle).
• No audio prompts: Guidance tones or system alerts routed through the display system may be absent.
• Intermittent operation: Features work sometimes, then drop out with bumps, temperature changes, or vibration.
• Multiple network codes: Additional U-codes may be stored in several modules, indicating a broader network communication problem.

Common Causes

• Open, high-resistance, or shorted wiring in the network communication circuits between the navigation display module and the rest of the vehicle network
• Loose, backed-out, damaged, or corroded terminals at the navigation display module connector or an in-line network junction/connector
• Loss of power feed to the navigation display module (blown fuse, faulty relay, open in the power supply circuit)
• Poor module ground (ground fastener issue, corrosion, broken ground lead, high resistance in the ground path)
• Network wiring fault elsewhere on the same bus (short-to-ground/short-to-power/open) that prevents multiple modules from communicating
• Intermittent connection caused by harness movement, poor pin fit, or connector strain near the display/module mounting area
• Navigation display module internal fault (hardware failure) after verifying power, ground, and network integrity
• Software/configuration issue affecting network participation or wake/sleep behavior (varies by vehicle; confirm with service information)

Diagnosis Steps

Tools that help: a scan tool capable of full-network scans and module identification, a digital multimeter, and service information with wiring diagrams, connector views, and network topology for the vehicle. Back-probing tools, terminal tension tools, and a battery charger/maintainer are also useful to keep system voltage stable during testing and to avoid creating intermittent faults while probing.

1. Confirm the complaint and capture data. Verify the navigation display concern (blank screen, rebooting, no navigation display, etc.). Pull all stored and pending DTCs from every module, not just one. Save freeze-frame or event records and note which modules report “lost communication” and which module(s) cannot be accessed.
2. Check for a wider network issue. If multiple U-codes are present across many modules or several modules are not reachable, treat this as a possible network-wide fault rather than a single display issue. Use the scan tool network report to identify whether communication loss is isolated to the navigation display module or affects a whole bus segment.
3. Verify battery/charging system stability. Low or unstable system voltage can cause modules to drop off the network. Confirm the battery is in good condition and that system voltage is stable during key-on and engine running conditions. Correct power supply issues before deeper network diagnosis.
4. Perform a visual inspection of the module area. Inspect the navigation display module and its harness routing for signs of pinched wiring, abrasion, recent repairs, loose connectors, or strain at the connector. Gently manipulate the harness to see whether the display or scan-tool communication changes (do not force connectors).
5. Check fuses and switched feeds for the module. Using service information, identify all constant and ignition/switched power feeds supplying the navigation display module. Test the related fuses under load where possible and confirm the module receives the required power in the correct key positions (varies by vehicle). Do not assume a visually “good” fuse is electrically good.
6. Voltage-drop test the ground path. With the module powered (key-on as required), perform voltage-drop testing from the module ground pin(s) to the battery negative while the circuit is loaded. Excessive drop indicates high resistance in the ground path. Inspect ground points, fasteners, and splices; clean/repair as needed and retest.
7. Validate the network circuits at the module connector. With the ignition off and following service information precautions, disconnect the navigation display module and inspect terminals for corrosion, spread pins, or poor retention. Check for continuity and shorts (to ground, to power, and between network lines as applicable) in the network communication circuits between the module connector and the next network junction. Repair wiring faults found and recheck.
8. Wiggle test for intermittents while monitoring. Reconnect and re-power the system. Monitor live network/module status (module online/offline, communication errors, or message counters if available). Perform a controlled wiggle test of the harness and connectors at the module, nearby junctions, and along known pinch points. If the fault toggles, focus on the section that reproduces the issue.
9. Check network integrity on the affected bus segment. If U0156 is accompanied by other communication codes on the same bus, isolate sections using the wiring diagram and connector/junction locations. Disconnect components one at a time as directed by service information to see whether communication returns, indicating a bus-disrupting short/open in a specific branch.
10. Confirm module wake and configuration factors. Some vehicles require the navigation display module to wake via an ignition signal, wake line, or network wake message. Verify the module receives required wake inputs and that no related DTCs (power mode, gateway, anti-theft, or configuration) explain why the module remains offline. This portion is vehicle-dependent; follow service information.
11. Make a repair decision only after circuit proof. If power feeds, grounds (via voltage-drop), and network circuits test good, and the module remains non-communicative or repeatedly drops offline, suspect an internal module fault. Before replacement, confirm connector terminal tension, verify no intermittent opens, and ensure the network is stable with other modules present.

Professional tip: If the navigation display module intermittently appears and disappears on the scan tool, prioritize finding a high-resistance power/ground or terminal-fit issue rather than condemning the module. Log network/module status while performing a gentle harness/connector wiggle test, then follow up with voltage-drop testing on the exact feed/ground circuits that correlate with the dropout to pinpoint the location.

Possible Fixes & Repair Costs

Repair costs vary widely because the same “lost communication” code can be caused by anything from a simple connector issue to a module power/ground fault or network wiring problem. Confirm the root cause with testing before replacing parts.

• Restore navigation display module power and ground (repair open/high-resistance feeds, clean/tighten ground points, replace damaged terminals as needed)
• Repair network wiring faults affecting the module (open circuits, shorts between network lines, or shorts to power/ground; repair harness routing or chafing)
• Service connectors in the communication path (reseat, correct poor pin fit, remove corrosion/contamination, repair water intrusion sources if found)
• Correct related module or gateway issues that disrupt network traffic (verify other network modules for related U-codes and repair the shared fault)
• Update or reconfigure module software only when service information calls for it and all wiring/power/ground checks pass
• Replace the navigation display module only after verifying it has correct power/ground and the network circuit integrity is good

Can I Still Drive With U0156?

In many vehicles, U0156 mainly affects navigation and related display functions, so the vehicle may remain drivable; however, communication faults can overlap with other network issues. If you have warning indicators for critical systems, reduced power behavior, no-start, stalling, or any steering/brake-related warnings, do not drive and have the vehicle inspected. If the only symptom is loss of navigation display features, drive cautiously and schedule diagnosis soon, as the underlying network fault can worsen intermittently.

What Happens If You Ignore U0156?

Ignoring U0156 can lead to persistent or worsening loss of navigation display functions, intermittent screen dropouts, and expanding communication errors as the network fault progresses. A marginal power/ground, connector, or harness issue can become more frequent over time, potentially causing additional modules to log communication DTCs and complicating diagnosis later.

Last updated: March 15, 2026

Vehicles Commonly Affected by U0156

• Vehicles equipped with an integrated navigation display module on the communication network
• Vehicles where the center display is a network node that also hosts infotainment/navigation functions
• Vehicles with multiple network segments linked by a gateway module
• Vehicles with recent dash, audio, or display-related repairs where connectors may be disturbed
• Vehicles exposed to moisture intrusion near the dash, console, or module mounting areas
• Vehicles with known harness flex points near the dash frame or steering column area (varies by vehicle)
• Vehicles with aftermarket electrical additions tied into power, ground, or network wiring (varies by vehicle)
• Vehicles with higher network traffic and multiple driver-assistance/infotainment modules sharing the bus (varies by vehicle)

For a reliable repair, confirm the fault with repeatable testing, fix the verified power/ground/network issue, and then recheck communication and codes to ensure U0156 does not return.