What the diagnostic plug can send
An in-vehicle OBD terminal (on-board diagnostics) reads ECU engine data, speed, fuel use, and DTC fault codes from the OBD-II port, then sends them over 4G. Fleets, UBI insurance, remote diagnosis, and driving-behavior analysis all start there. The dongle has to be small and low power because it lives in that port. SimtoLink modules for this work are 4G / LTE Cat.1 / NB-IoT, industrial-grade, with UART and SPI. The company supports 500+ enterprise customers and has connected more than 10 million OBD devices.
Fleets, insurance, and a rented car
A truck fleet, a UBI policy, a remote diagnosis, and a rental car all read the same port. They do not report at the same rate. These are the usual OBD jobs, and the radio that tends to fit.
Commercial fleets
Truck and taxi dongles report fuel, distance, hard acceleration and hard braking, and CAN bus data over 4G. Dispatch, driving behavior, and a TMS link all use that, which is how operating cost comes down.
UBI priced on how the car is driven
Driving behavior goes to the insurer through the module, for Pay-As-You-Drive pricing. Safer drivers can pay less, which is the point of the product.
Remote diagnosis
DTC codes, engine parameters, and ECU data go up through the module. A workshop can troubleshoot from a distance, suggest a repair, and warn before the car stops, so the fault is shorter and the driver is not left guessing.
Rental cars and time-share fleets
A rental car's OBD terminal reports distance, theft risk, a geofence, and unusual use. Electronic contracts and billing by time both sit on that record, which is how rental risk stays down.
BMS data on a new-energy vehicle
BMS data and SOC go up over OBD or a dedicated port. Battery health, charging, and remote diagnosis all use that, which is what the driver of an electric vehicle actually feels.
J1939 on heavy vehicles
Heavy trucks and construction machines read the CAN bus over J1939: fuel, engine condition, and urea level. A commercial fleet cannot manage those vehicles without that report.
What a dongle in the port asks of the module
- Coverage as the vehicle crosses regions: Several operators and bands are what hold coverage and roaming handover.
- Small, and able to sleep: The terminal plugs into the diagnostic port, so the module has to be small, draw little on standby, and be plug-and-play.
- Temperature and vibration in the cabin: −40°C to 85°C, and resistance to vibration, for a long life in the vehicle.
- The diagnostic chip the port already uses: An OBD protocol chip such as ELM327, plus GNSS, over OBD-II, J1939, and ISO 15765.
- From a sample to volume: SimtoLink modules span 2G, 3G, 4G, and 5G, with documentation, an AT command set, an SDK, and production supply.
Which radio fits a dongle
How often it reports, the pipe, and cost do not line up the same way for a live fleet and a weekly mileage count. Vehicle type, the job, and power should decide the module. The rows below are the usual pairing for OBD.
| Job | Radio | What matters |
|---|---|---|
| Fleets, UBI insurance, remote diagnosis | 4G LTE Cat.1 | Live reports, driving behavior, DTC, fuel and distance, cost against bandwidth |
| Rental vehicles, low-frequency reporting | LTE Cat.1 | Distance, a geofence, daily or weekly reports, low cost |
| Distance and fuel only | NB-IoT | Very low power, infrequent reports, cost first |
| Commercial vehicles J1939 | 4G | J1939, CAN data, live reports, several operators |
How SimtoLink fits an OBD program
For dongles, the modules are industrial designs that hold temperature and vibration, with technical support 7×24. LTE Cat.1 or 4G is the recommendation when cost and a live report both matter. NB-IoT fits a cost-first job such as infrequent distance counts. An SDK a terminal team can bring up quickly, work with mainstream chip vendors, and a named account manager come with the module.
A dongle is taken from the requirements and the radio choice, through a prototype in a few vehicles, and into volume. Documentation, the AT command set, an SDK, and sample code ship with the module, and supply is planned for a production run and for later years. Fleet management and UBI insurance keep adding vehicles that need a radio, and the module line will follow that.
How an OBD project usually moves
An OBD project usually moves in this order:
The choice turns on the vehicle (a passenger car on OBD-II, a commercial vehicle on J1939), how often it reports (live, daily, or weekly), protocol fit (OBD-II, J1939, ISO 15765), and the cabin (vibration and a wide temperature range). Start with a small set of vehicles and check that the read is right, the protocol matches, and the platform link holds. An OBD terminal should use LTE Cat.1 or 4G when the report has to be live.
The radio in the port is what fleets, UBI insurance, remote diagnosis, and rental fleets stand on. SimtoLink has supplied modules to fleet, insurance, and rental customers.