SimHub troubleshooting

Start here: what is it doing?

The three things to try before anything specific

1. Disable third-party plugins. The official troubleshooting page names them as the number one cause of SimHub instability. This is the first diagnostic step, not a last resort, and it costs nothing to test — if the problem goes away, re-enable them one at a time.
2. Restart SimHub. Some changes are not picked up live: a COM port that Windows reassigned, a port number changed in settings, a newly installed plugin. This is not generic advice, it is a real requirement in specific documented cases.
3. Check you are on a current version. SimHub ships frequently. This cluster is checked against 9.11.22; several releases landed in the weeks before it.

SimHub won't start

The characteristic failure is a hang at Initializing: CoreData with no error dialog. That is .NET Framework 4.8 missing — install it and restart.

If .NET is present, suspect a plugin. Failing that, climb the reset ladder in order, and read the warning on the second rung before you get there.

Local User Settings Reset deletes your licence. It clears %localappdata%, which is where the licence lives alongside your settings, profiles and dashboards. Back that folder up before running any reset. Full details on the dedicated page.

SimHub runs but sees no telemetry

Four causes cover almost all of it:

• The game is not enabled in SimHub's settings. Only games you tick are watched.
• Admin rights do not match. If the game or its launcher runs as administrator, SimHub must too — a non-elevated process cannot read an elevated one's shared memory. This is the cause people find hardest to guess.
• A per-game step is missing. iRacing needs irsdkEnableMem=1; Euro Truck Simulator 2 and American Truck Simulator need SimHub's telemetry plugin installed into the game.
• Something else has the UDP stream. Only one application can receive it — see below.

It stopped working when you opened another app

This is worth its own entry because the symptom is confusing: everything worked, you opened CrewChief or Track Titan or a second dash application, and SimHub went blank.

A UDP stream can only be received by one application. Games that broadcast telemetry over UDP — the Forza titles, the Codemasters and F1 games, Project CARS, Gran Turismo — send to one port, and whichever app claims it first gets it. The second app gets nothing.

The fix is UDP forwarding: SimHub can re-broadcast what it receives to other ports and IP addresses, so it takes the stream and passes it on. The dedicated page covers the setup.

Dashboards lag, or the game loses frames

Usually not the dashboard itself. In rough order:

• The GPU is already at 90–95% load. SimHub renders with WPF, which is GPU-accelerated, so it is competing with the game for the same resource. An FPS limiter in the game is the first thing to try.
• Adaptive sync. G-Sync and FreeSync interfere with how SimHub renders. Set adaptive sync to fullscreen-only, or add a SimHub exception.
• Mismatched monitor refresh rates across a multi-monitor setup.
• Process throttlers. Windows Game Mode, Process Lasso, Norton Game Optimizer and MSI's X3D Mode all deliberately starve non-game processes — which is exactly what SimHub is.
• Oversized overlays. A transparent area still costs you; overlay surfaces are capped at 480,000 pixels for this reason.

There is also an alternative HTML rendering engine selectable per dashboard, which is worth trying when one specific dashboard misbehaves and others do not. Full detail on dashboard performance.

Gathering diagnostics before you ask for help

If you are going to ask someone else, arrive with these — it is the difference between an answer and twenty questions.

• The System Informations page inside SimHub. It reports your version, .NET, hardware and detected devices in one place.
• Your SimHub version, exactly. "The latest" is not a version; releases land often enough that it means nothing a week later.
• The game, and how its telemetry works — UDP, shared memory, or a SimHub-installed plugin. The games index explains which is which.
• What changed. Windows update, new plugin, new hardware, moved USB port. Something almost always did.

Where to get help

Discord is the primary channel now. Registration on the SimHub forum has been paused because of spam, so the forum is largely read-only for newcomers. It remains an excellent archive — searching it is often faster than asking — but if you need to ask a question, Discord is where people are.

• The official wiki — 71 pages, and the best reference for Arduino wiring. Written for people who already know the architecture.
• The SimHub forum — read and search freely; the Dashboard Templates section alone runs to nearly 1,900 posts.
• GitHub issues on SHWotever/SimHub — around 388 open at the time of writing, and often the only place a specific bug is acknowledged.

Everything in this section

• Arduino not detected Cables, the generic CH340G driver break, COM ports, scan settings, power and unsupported boards.
• Two iFlags, only one works Two iFlags — or any two identical devices — both plugged in, one dark, each fine alone: they share a device name, so they share a USB signature.
• Game not detected Enabling games, admin-rights mismatches, per-game plugins and firewall rules.
• UDP conflicts with CrewChief Why only one app gets the stream, and how UDP forwarding fixes it.
• SimHub won't start The CoreData hang, plugin faults, and the reset ladder that deletes your licence.
• Antivirus and false positives Why Defender flags it, and the fix ladder that does not involve turning your antivirus off.
• Bass shakers silent Audio device, exclusive mode, enhancements, Voicemeeter and the 48kHz requirement.
• Dashboard lag and FPS drops GPU load, adaptive sync, process throttlers and the alternative rendering engine.
• Govee lights won't work Supported since 8.3.0 — but only Dreamview models, only with LAN control on, and only if nothing else is controlling the light.
• Which smart lights work Govee, Hue, Chroma, Bluetooth and DIY compared, with each one's hard ceiling on areas.
• Philips Hue Entertainment mode needs a bridge and an area you create in the Hue app first.
• Razer Chroma Five areas, defined by the manufacturer rather than by you, and higher latency.
• Bluetooth flood lights BLE on the PC, and your phone silently reclaiming the light is why they stop.
• Devices randomly disconnecting Two Windows power settings fix most of it. Then cables, and the sound card that takes others down.
• Vocore screen freezing Documented USB instability. Firmware first, with the official v2scrctl tool.
• Phone dashboard won't connect One loopback test splits it into server or network, so you can skip half the advice.
• SimHub breaks my button box Its Arduino scan probes serial ports. Limit the scan, or turn Arduino support off.
• The board you bought won't work Uno R4 is unsupported. WAVGAT, ATmega168p Nanos and unlabelled CH340G chips are the fakes.
• Encoders skipping or double counting Timing type, missing pull-ups, or the pin. EC11s work; Leo Bodnar encoders do not.
• LEDs dim, wrong colour or resetting Four symptoms, one cause. And the wiring rule that costs hardware rather than time.
• Moving to a new PC One folder, two deletions — and four things that do not come with it.
• Nextion stopped working Support ended but was not removed. The plugin is disabled by default now.
• Licence and activation Copies are not reissued once activated, which makes the purchase email a backup artefact.

Common questions

Sources

• SimHub wiki
• SimHub community forum
• SimHub issues on GitHub

Related guides

• Installing SimHubRequirements, SmartScreen, and where SimHub keeps the things a reset would delete.
• Per-game setupWhich games use UDP, which use shared memory, and what each one needs enabling.