B1321 – Lost communication with electro multi vision (EMV) missing message (Toyota)

Toyota-specific code — factory diagnostic data

B1321 means the Toyota Yaris lost communication with the Electro Multi Vision (EMV) system, so some display or information functions may stop working or act erratically. You will usually notice screen-related features missing, delayed, or resetting before you notice any drivability change. According to Toyota factory diagnostic data, this code indicates a “lost communication with EMV” condition caused by a missing network message. The combination meter sets this code when it expects a specific EMV message and does not receive it within the required time. That points you toward network integrity, EMV power/ground, and connector issues before any module replacement.

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B1321 Quick Answer

The combination meter is not receiving a required EMV message on the vehicle network. Diagnose the communication path first: power/ground to EMV, connectors, and the related network wiring.

What Does B1321 Mean?

Official definition: Lost communication with electro multi vision (EMV) missing message. In practice, the combination meter cannot “see” a message it needs from the EMV system, so display-related information may be incomplete or unavailable. The code does not prove the EMV unit failed. It only proves the message did not arrive when expected.

What the module checks: The combination meter monitors network message presence and timing for EMV-related data. When that message goes missing, it flags a communication loss DTC. Why that matters: A missing message can come from a dead EMV, a network wiring fault, poor grounds, connector fretting, or a network segment problem. Per SAE J2012-DA guidance, the DTC identifies a suspected trouble area and you must test to find the root cause.

Theory of Operation

Under normal operation, Toyota modules share data across the in-vehicle network so the combination meter can display alerts, status, and driver information. The EMV system publishes specific messages, and the combination meter subscribes to them. The meter expects those messages repeatedly while the system stays awake.

B1321 sets when the combination meter stops receiving the required EMV message. A loss of EMV power or ground can silence the transmitter. Network faults can also corrupt or block the message. Intermittent connector contact can create a pattern where the message disappears, returns, and disappears again.

Symptoms

Drivers and technicians usually notice one or more of these symptoms when B1321 sets:

• Scan tool EMV-related module may not respond, may drop off the ECU list, or may show intermittent communication
• Display missing screens, missing vehicle information, or blank sections where data normally appears
• Resets screen or display functions restart unexpectedly during a drive
• Warnings cluster messages that indicate an information/display system malfunction
• Intermittent symptoms change with bumps, temperature, or steering column tilt adjustments
• Multiple DTCs other communication or “missing message” codes stored in several modules
• Battery sensitivity symptoms appear after a low battery event, jump start, or battery replacement

Common Causes

• EMV unit not reporting on the network: If the electro multi vision (EMV) stops transmitting its expected message, the combination meter logs a missing-message communication loss.
• Open or high-resistance power feed to the EMV: A weak supply can let the EMV boot inconsistently and drop off the bus, which looks like lost communication.
• High-resistance ground at the EMV or splice pack: Ground voltage rise under load can interrupt module operation and corrupt message traffic.
• Connector fretting, corrosion, or poor terminal tension: Small increases in contact resistance can cause intermittent bus dropouts and message loss.
• CAN communication line open circuit: An open in CAN wiring between the EMV and the rest of the network prevents the combination meter from seeing the EMV message.
• CAN communication line short to ground or short to battery: A short can collapse bus signaling or hold a line dominant, which prevents normal message exchange.
• Harness damage near moving or pinch points: A chafed harness can create intermittent opens or shorts that appear only with vibration or steering column movement.
• Network disruption from another module or accessory: A failing node or an incorrectly installed accessory can load the bus and cause the EMV message to disappear.

Diagnosis Steps

You need a scan tool that can perform a Toyota health check or network scan, view freeze frame, and read body DTCs. Use a quality DVOM and a test light or loaded probe for power and ground checks. A backprobe kit helps prevent terminal damage. If the fault acts intermittent, use a scan tool snapshot or datalog during a road test.

1. Confirm B1321 in the combination meter and record freeze frame data. Focus on ignition state, battery voltage, vehicle speed, and any related communication or body DTCs. Freeze frame shows conditions when the code set. Use a scan tool snapshot later to capture live data during an intermittent dropout.
2. Run a full network scan and note whether the EMV appears as an online module. If the scan tool cannot communicate with the EMV, treat the problem as power/ground or network wiring first. If the EMV communicates, treat the problem as intermittent message loss or a network quality issue.
3. Check fuses and power distribution that feed the EMV and related body/AV circuits. Verify each fuse carries load, not just continuity. Use a test light or loaded circuit tester. A fuse can pass continuity and still fail under load due to heat damage at the blades.
4. Verify EMV power and ground at the EMV connector using voltage-drop testing under load. Command the system on so the EMV draws current. Measure voltage drop from battery positive to the EMV B+ pin. Measure ground drop from the EMV ground pin to battery negative. Keep ground drop below 0.1 V with the circuit operating.
5. Inspect EMV and combination meter connectors and nearby harness routing. Look for backed-out terminals, water tracks, green corrosion, bent pins, and poor terminal tension. Do not spread terminals with oversized probes. Re-seat connectors and confirm locking tabs fully engage.
6. Wiggle-test the harness while monitoring the scan tool network status and EMV-related data. Move the harness at known stress points and connector exits. If B1321 flips from pending to current, or the EMV drops offline, isolate the exact movement that triggers the failure. Use that location for a close visual and pin-fit inspection.
7. If the EMV stays offline, check CAN bus integrity with ignition OFF and the battery disconnected. Measure resistance between CAN+ and CAN- at an accessible module connector on the same bus. A healthy bus reads about 60 ohms. Readings near 120 ohms or OL point to an open or missing termination, which can cause missing messages.
8. With ignition ON, check CAN bias voltage to ground at the same access point. Communication bias exists only with the network powered, so ignition-off readings mislead you. A healthy bus typically sits near 2.5 V on both CAN+ and CAN- to ground. A pulled-up or pulled-down line suggests a short to battery or ground, or a failed node loading the bus.
9. If measurements indicate a short, isolate the fault by disconnecting modules on the affected bus one at a time. Start with the easiest-to-access connectors and any recent accessory connections. Each time, recheck CAN resistance and bias voltage. When the bus returns to normal, the last disconnected branch contains the fault.
10. After repairs, clear DTCs and run another network scan. Confirm the EMV shows online and communicates consistently. Road test under the freeze frame conditions when possible. Recheck for pending versus confirmed status, since some Toyota body communication faults may require more than one key cycle to mature.

Professional tip: Treat the FTB suffix as a diagnostic direction, not a parts verdict. For Toyota missing-message faults, a clean power and ground voltage-drop test often saves hours. Many “bad modules” come back to a ground splice with hidden resistance. Always prove the network is healthy before you condemn the EMV or the combination meter.

Possible Fixes

• Restore EMV power supply integrity: Repair open feeds, poor fuse contact, or damaged power wiring found during loaded testing.
• Restore EMV ground integrity: Clean and tighten ground points, repair ground splices, and replace damaged ground wiring that fails voltage-drop testing.
• Repair CAN bus wiring faults: Fix opens, shorts to ground, or shorts to battery in the CAN pair, and correct any pin fit issues at connectors.
• Correct connector terminal issues: Replace or re-tension terminals that show corrosion, looseness, or evidence of fretting.
• Remove or rework interference from accessories: Correct aftermarket wiring that loads the network or shares power/ground improperly.
• Replace a confirmed failed module only after verification: Replace the EMV or another identified node only after power/ground and bus tests prove the module stops network recovery when connected.

Can I Still Drive With B1321?

You can usually drive a Toyota Yaris with B1321, because the fault sits in the body communication network. The combination meter logs this code when it stops receiving the expected EMV message. That often affects display, warning chimes, or information sharing between modules. Treat it differently if warning lamps stack up or gauges act wrong. If the speedometer, ABS, or brake warnings appear, stop and diagnose before more driving. A communication loss can also mask other faults, so avoid long trips until you confirm the network stays stable.

How Serious Is This Code?

B1321 ranges from an inconvenience to a serious electrical problem. It stays minor when you only lose EMV-related display functions and the vehicle drives normally. It becomes more serious when the communication dropouts spread across the network. Multiple U-codes, random warning lamps, or intermittent no-start can point to a power, ground, or bus integrity issue. The FTB suffix “-87” maps to SAE J2012DA “No Signal.” That subtype fits a missing message event, not a confirmed module failure. Prove the network and module powers first.

Common Misdiagnoses

Technicians often replace the EMV unit because the code text names it. That wastes money when the real fault sits in shared power, shared ground, or the communication lines. Another common error involves clearing codes and declaring success without verifying message traffic under vibration and heat. Some shops also chase the wrong module because B1321 logs in the combination meter. The meter acts as the reporter, not always the cause. Avoid these traps by checking for companion network DTCs, verifying EMV powers and grounds with a loaded voltage-drop test, and confirming bus signal integrity at the connectors.

Most Likely Fix

The most frequent confirmed repair involves restoring stable power or ground to the EMV or the network junction it shares. Corrosion, loose pins, or a backed-out terminal can cause a clean “No Signal” missing message. A second common direction involves repairing a high-resistance or intermittently open communication line between the EMV and the rest of the network. Do not treat either as certain until you verify connector fit, perform voltage-drop tests under load, and confirm the EMV appears consistently in the scan tool network list.

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 8, 2026