OBD-2 Telematics Monitors — How They Work

Updated October 2026 · Fleet Genius

System Architecture

An OBD-2 telematics system has three layers: the in-vehicle device (data collection), the cellular/satellite network (data transmission), and the cloud platform (data processing and storage). Data flows from the vehicle's CAN bus through the OBD-2 port to the device, which packages it into messages sent over LTE (or satellite in remote areas) to the cloud.

Reading the CAN Bus

The Controller Area Network (CAN) bus is the vehicle's internal communication backbone. The OBD-2 port exposes a subset of CAN messages defined by SAE J1979 (diagnostic services) and J1850/ISO 15765 (transport protocols). The telematics device sends standardised PID (Parameter ID) requests and decodes the responses into human-readable values — RPM, speed, temperatures, fuel trim.

Data Transmission

• Real-time streaming — GPS position every 10–60 seconds; engine data every 30–120 seconds.
• Event-triggered — harsh braking, DTC, geofence entry/exit sent immediately.
• Store-and-forward — if the device loses cellular coverage, data is buffered in flash memory (typically 72 hours) and uploaded when connectivity returns.

Cloud Processing

Raw CAN data is decoded, normalised, and enriched in the cloud. The platform maps PID responses to vehicle-specific parameters (a Ford F-150's coolant temp PID returns Celsius; the platform converts and applies model-specific thresholds). Machine-learning models analyse patterns — a gradually rising coolant temperature trend may predict a water-pump failure days before a DTC fires.