OBDLink adapters (MX+, EX, SX, LX, CX): STN chips, MS-CAN, and Windows software

OBDLink is the adapter line from OBD Solutions (obdlink.com). From the outside these look like any other dongle you push into the OBD-II port. Inside sits the company's own STN interpreter chip rather than a copy of somebody else's ELM327 die, and that single fact drives every difference discussed below. As of September 2026 the line is five models: MX+, EX, CX, LX and SX. Diagnost talks to all five, and it drives them with their native ST commands instead of treating them as expensive ELM327 clones.

Two questions bring people here: which model to buy, and what to run on it once the bundled software runs out of road. Both are answered below. If you already own the adapter and only need software, go straight to OBDLink software for Windows.

Which model reaches which bus

Model choice comes down to two axes: how the adapter reaches your computer or phone, and how many of the car's networks it can physically touch. Everything else is firmware.

The asymmetry catches people out: EX has MS-CAN but not SW-CAN. If your car is an Opel, Chevrolet, Cadillac or Buick and you want body modules, EX will not get you there — MX+ will. Street prices run several times an ELM327 clone, with MX+ at the top of the line; check the vendor for current figures rather than trusting a number in an article.

The STN chip family

Every model runs a chip from the STN series. By the chip maker's own documentation the mapping has historically been STN1130 in the SX and STN1155 in the LX — single-bus parts — while STN1170 and its successor STN2120 are the 44-pin parts that carry SW-CAN and MS-CAN transceivers on top of standard OBD-II. OBD Solutions now steers new designs to the STN2120, which matches the STN1170 feature for feature with double the flash and four times the RAM at the same cost. The MX+ is built on the STN2255.

Formally these are OBD-to-UART interpreters, same category as the ELM327. In practice four things separate them.

• Receive buffers. More RAM means a long module response arrives whole. Truncated replies are the classic ELM327 clone failure: half a fault list comes back and the software concludes the module is silent.
• Hardware message filters. STFAP passes, STFAB blocks and STFAFC handles flow control, all inside the adapter. The host program receives only the CAN IDs it asked for instead of the whole bus, which is what keeps a graph of a dozen live PIDs from stuttering.
• Protocol presets. One STP command selects a ready channel instead of hand-tuning ATSP: 33 is ISO 15765 on 11-bit IDs at 500 kbps, 53 is the same on MS-CAN at 125 kbps, 63 is SW-CAN at 33.3 kbps. STPO opens the channel, STPC closes it, STPTO sets the request timeout.
• Single-wire transceiver control. STCSWM puts the SW-CAN transceiver into a chosen mode: 3 is normal and is applied automatically when a SW-CAN protocol opens, 2 is high-voltage wakeup, 0 is sleep on close. Without mode 2 the sleeping GM body modules simply never answer.

One constraint applies to every model: only one CAN channel is live at a time, because the die carries a single CAN peripheral. Software walks HS-CAN, then MS-CAN, then SW-CAN in sequence; nothing listens to all three at once.

MS-CAN and SW-CAN: the pins a plain ELM327 never wires

Everything the premium models cost extra for lives on three contacts of the J1962 connector.

Why FORScan cares about the switch

Cheap Ford adapters expose MS-CAN with a physical toggle: flip it and the dongle is rewired onto pins 3 and 11. The problem is that anything needing both networks in one session — and several FORScan procedures do — cannot work that way. OBDLink switches electronically under software control, which is why the FORScan team recommends the EX and why the vendor quotes throughput up to twenty times that of toggle-switch adapters. Diagnost uses the same mechanism through the STP presets, so a full-vehicle scan on a Ford covers powertrain and body without you touching the adapter.

OBDwiz and what sits above it

Every OBDLink ships with OBDwiz for Windows 7 SP1 through 11 at no extra cost, and it is a genuinely competent generic OBD-II tool: read and clear engine codes, more than ninety PIDs, oxygen sensor results in mode $05, on-board monitoring in mode $06, vehicle information in mode $09, emissions readiness against a built-in standards database, custom dashboards, and logging to file. For a check engine light that is all you need.

What its published feature list deliberately stops short of is manufacturer-specific territory — the modules that live beyond the legislated OBD-II modes.

Drivers, pairing, and firmware on Windows

USB models (SX, EX) enumerate as an FTDI virtual COM port. Windows 10 and 11 usually install the driver on first plug-in; if not, the driver download sits on the model's support page. A red LED on connection to the PC and a "USB device not recognized" message both mean the driver did not take.

Bluetooth models (MX+, LX) pair like ordinary Windows devices, but in Settings the Bluetooth device discovery has to be switched from Default to Advanced or the adapter never appears. The PIN is 0000, or a numeric comparison prompt. The MX+ adds a physical Connect button: pairing only opens when you press it, and the adapter does not continuously broadcast its presence. That is the quiet security argument against no-name clones, which sit in the parking lot advertising themselves with PIN 1234 to anyone who scans.

CX is Bluetooth Low Energy only. Pick the matching link type in your software: Bluetooth for MX+ and LX, Bluetooth LE for CX, USB for SX and EX.

Firmware updates are free and handled by the STN Firmware Updater utility. Run it once at a desk before your first session.

What Diagnost reads over an OBDLink, by make

The middle column is what any model in the line delivers over the main bus. The right column is what appears only when the adapter can reach a second network.

Connection problems and what fixes them

• Adapter never shows in the Bluetooth list. Set device discovery to Advanced in Windows settings, and press the Connect button on an MX+ — unpressed, it stays invisible.
• Windows shows the paired adapter as "Not connected". That is normal standby, not a fault. The link comes up when a program opens the COM port.
• Port busy or access denied. One program at a time owns the port. Close the vendor app or a second scan tool before starting Diagnost.
• Red LED and "USB device not recognized" on SX or EX. The FTDI driver did not install. Install it by hand, try another port, or go through a USB 2.0 hub.
• Second-bus modules never answer. Confirm the model: SW-CAN needs MX+, MS-CAN needs MX+ or EX. SX, LX and CX lack the transceivers, and no software can add them.
• GM body modules silent on a healthy MX+. They are asleep. Turn the ignition on and rescan; the program issues STCSWM 2, the high-voltage wakeup mode, before probing.
• Adapter behaves oddly after another app used it. Unplug and replug. A power cycle restores the firmware defaults.

When a cheaper adapter is the honest answer

Plenty of people do not need this hardware. If you pull an engine code once or twice a year, a v1.5 ELM327 clone reads P0420 or P0300 exactly as well, and on many cars you can skip installing anything and read engine codes in the browser.

OBDLink earns its price in three situations: a Ford, Mazda or Opel whose interesting modules sit on the second bus; long live-data sessions where sample rate and stability matter; and an adapter that stays in the port permanently and must sleep properly. For BMW, buy a K+DCAN cable for E-series and early F cars or an ENET cable for G and I — both cost around ten dollars and go far deeper than any OBDLink can over the standard port. For dealer-grade interfaces you may already own, see J2534 pass-thru devices. Communication faults such as U0100 or U0155 are often the hint that the module you need is not on the bus you are watching.