U0185 – Lost Communication With TV/Telematics Unit

U0185 means your vehicle lost communication with the TV/Telematics Unit, so connected services and some infotainment-related features may stop working. Drivers usually notice SOS/telematics warnings, no cellular connection, or intermittent audio/navigation behavior. According to factory diagnostic data, this code indicates the network cannot exchange valid messages with the telematics unit for a required period. The code does not prove the telematics unit failed. It only proves another module stopped “hearing” it on the network. Your first job is to confirm if the unit is missing from the network scan, then verify power, ground, and network wiring.

U0185 Quick Answer

U0185 points to a communication loss with the TV/Telematics Unit. Check whether the telematics module shows up on the scan tool network list, then verify its fuses, grounds, and network connector pins before you consider replacing anything.

What Does U0185 Mean?

U0185 meaning: “Lost Communication With TV/Telematics Unit.” In plain terms, one or more control modules expected updates from the telematics unit and did not receive them. That usually affects SOS/assist functions, embedded cellular data, remote start through an app, vehicle tracking, or infotainment features tied to the telematics gateway. Some vehicles also log secondary warnings because other modules share data through the same network path.

Technically, a module monitors network message traffic and expects the telematics unit to transmit identified messages at normal intervals. When those messages stop, the monitoring module sets the U0185 code and may flag the telematics ECU as “not responding.” SAE J2012-DA makes U-codes intentionally general. Diagnosis must confirm whether the issue comes from power/ground loss at the telematics unit, an open/short on the bus, a connector fault, or a network gateway that blocks traffic.

Theory of Operation

Under normal conditions, the TV/Telematics Unit powers up with ignition or with a keep-alive feed. It then joins the vehicle network and broadcasts status and request/response messages. Other modules may use that data for emergency calling, time and location services, remote commands, and infotainment integration. Depending on the platform, the telematics unit may sit on HS-CAN, MS-CAN, a private CAN, or a LIN branch behind an infotainment gateway.

U0185 sets when the expected message flow stops. A blown fuse, weak ground, or excessive voltage drop can reset the telematics unit and make it disappear from the network. Corrosion in a roof-mounted or trunk-mounted connector can add resistance and distort network signals. Harness damage can also short CAN lines together or to power or ground. A gateway module can create the same symptom if it stops routing traffic between buses.

Symptoms

U0185 symptoms usually involve telematics, connected features, and scan tool network behavior.

• Scan tool: TV/Telematics Unit missing from the module list, shown as “no communication,” or drops out during a full network scan
• SOS/assist warning: SOS light on, telematics malfunction message, or emergency call system disabled
• Connected services: app remote commands fail, vehicle status will not update, or subscription services show offline
• Infotainment behavior: intermittent navigation data, time/date resets, or audio prompts tied to telematics stop working
• Battery draw concerns: parasitic draw complaints if the unit repeatedly resets or stays awake due to network faults
• Multiple U-codes: other modules store “lost communication” codes due to a shared bus, gateway, or power feed issue

Common Causes

• Telematics unit lost power feed (B+): An open fuse, failed relay, or high resistance in the B+ supply makes the TV/telematics unit drop off the network.
• Telematics unit ignition feed missing (IGN/RUN): A missing wake-up feed keeps the unit asleep, so other modules log U0185 when messages stop.
• High-resistance ground at the telematics unit: Corrosion or a loose ground eyelet lets the module boot intermittently and creates repeated communication loss.
• Connector fretting or water intrusion at the telematics module: Moisture and pin drag increase terminal resistance and interrupt network and power circuits under vibration.
• CAN/LIN network open, short, or intermittent near the telematics branch: A damaged twisted pair, pinched harness, or short to power/ground prevents valid network traffic to the unit.
• Aftermarket accessories loading the data bus: Remote starts, trackers, audio add-ons, or spliced power taps can distort bus signals or backfeed the telematics circuits.
• Module stays in reset due to undervoltage events: Weak battery, poor charging, or voltage drop during crank can reboot the telematics unit and trigger U0185.
• Gateway or network splice pack issue affecting the telematics leg: A fault at a junction connector or gateway path blocks messages even if the telematics unit itself remains powered.
• Telematics unit internal fault (rare): Internal hardware or software failure can stop message transmission, but you must prove power, ground, and bus integrity first.

Diagnosis Steps

Use a capable scan tool with full network scan, DTC status (pending/confirmed), and module information. Have a DVOM and back-probing tools for loaded voltage-drop tests. Pull the wiring diagram for the TV/telematics unit power, ground, and network circuits. A test light or fused jumper helps load circuits safely during checks.

1. Confirm U0185 and record DTC status in every module. Save freeze frame data and note ignition state, vehicle speed, battery voltage, and any network-related U-codes. Treat a pending U0185 as a one-trip event until it repeats, while a confirmed/stored code needs a hard fault search.
2. Run a full network scan and check if the TV/telematics unit appears in the module list. If the scan tool shows it as “no communication,” focus on power/ground and the local network leg first. If it communicates, look for intermittent dropouts and related codes in the gateway/body module.
3. Check fuses, relays, and power distribution that feed the telematics unit before probing the module connector. Load-test the fuse output with a test light or appropriate load, not just an ohmmeter. Verify the IGN/RUN feed switches on and stays stable during crank.
4. Verify telematics unit power and ground under load at the connector. Perform voltage-drop testing with the circuit operating. Target less than 0.1V drop on the ground path and minimal drop on the power feed while the unit remains powered.
5. Inspect the telematics unit connector, terminals, and nearby harness routing. Look for water tracks, green corrosion, bent pins, terminal spread, and evidence of prior accessory splices. Tug-test the harness lightly and check for intermittent changes on the scan tool network screen.
6. Check the network physical layer on the telematics branch. With ignition ON, measure communication line voltages at the telematics connector as a sanity check, since bus bias only exists when powered. Do not use ignition-OFF readings as a reference for network bias.
7. Isolate intermittent conditions with a scan tool snapshot. Use freeze frame to learn when the fault set, then trigger a manual snapshot during a road test or key-cycle routine to capture the moment communication drops. Correlate dropouts with crank, bumps, or accessory operation.
8. If the telematics unit does not appear on the network scan, unplug the telematics connector and recheck overall network behavior. A shorted module or shorted branch can pull the bus down. If other modules recover when unplugged, focus on the telematics unit and its branch wiring.
9. Perform continuity and short-to-power/short-to-ground checks on the telematics network circuits only after you confirm power and ground integrity. Disconnect the battery and required modules per service information to avoid backfeeding. Pay close attention to splice packs and inline connectors on the telematics leg.
10. After repairs, clear codes and rerun a network scan. Confirm the telematics unit communicates and U0185 stays cleared through at least one complete key cycle and a road test. If the monitor needs two trips to confirm, verify no pending U0185 returns on the next drive cycle.

Professional tip: Do not condemn the TV/telematics unit because it “won’t talk.” Prove B+, IGN, and ground quality with voltage-drop under load first. Many U0185 cases trace back to a weak ground, water intrusion in a connector, or an accessory splice that disturbs the bus.

Possible Fixes

• Repair power, ignition feed, or ground faults to the TV/telematics unit and confirm low voltage-drop under load.
• Clean, dry, and re-terminal telematics connectors that show corrosion, fretting, or terminal tension loss.
• Repair CAN/LIN wiring damage on the telematics branch, including splice packs and inline connectors.
• Remove or rework aftermarket accessory wiring that loads the network or backfeeds telematics power circuits.
• Address battery/charging issues that cause module resets, then verify stable voltage during crank and operation.
• Reprogram, update, or replace the TV/telematics unit only after you verify power, ground, and network integrity.

Can I Still Drive With U0185?

You can usually drive with a U0185 code because it reports a network communication loss, not a direct engine control failure. Expect the telematics, SOS, or connected services features to stop working. Some vehicles also lose the clock sync, remote start via app, or hands-free calling. Treat it differently if the telematics unit supports safety functions like automatic crash notification. In that case, driving stays possible, but you lose an emergency feature you may rely on. If the vehicle shows multiple U-codes, a dead cluster, or intermittent no-start, stop driving and diagnose the network and power feeds first.

How Serious Is This Code?

U0185 ranges from an inconvenience to a significant safety concern, depending on what the TV/Telematics unit does on that platform. If it only handles infotainment data and remote services, severity stays low. You mostly lose app features and SOS connectivity. If the unit routes audio prompts, microphone control, or crash notification, the impact grows. Network faults can also spread. A bus short or a module that pulls the network down can trigger multiple modules to drop offline. When you see repeated communication losses during a road test, treat U0185 as a network integrity issue that can create intermittent drivability complaints.

Common Misdiagnoses

Technicians often replace the telematics unit because the scan tool cannot connect to it. That mistake happens when the real issue sits upstream, like a blown module fuse, a weak ground, or water intrusion at an inline connector. Another common miss involves ignoring history and pending DTCs. A one-time U0185 after a battery swap can set without a hard failure. Shops also chase the wrong bus. Many vehicles use a gateway module, and the telematics unit may sit on a sub-network. If you do not confirm power, ground, and network pin integrity at the module connector, you can waste hours and parts.

Most Likely Fix

The most common U0185 repair path starts with restoring clean power and ground to the TV/Telematics unit. Check related fuses, wake-up feeds, and ground voltage drop under load. Next, inspect the telematics connector and nearby harness for water intrusion or backed-out terminals, especially near the trunk, rear quarter, or roof harness runs. If the scan tool still cannot see the module after you verify power, ground, and network wiring continuity, then module failure or a gateway issue becomes more likely. Confirm the network stays stable during a vibration or road test before you close the job.

Repair Costs

Network and communication fault repairs vary by root cause — wiring/connectors are often the source, but module-level repairs or replacements can be significantly more expensive.

Last updated: April 1, 2026