Vehicles, such as light-duty cars and trucks and heavy-duty tractor/trailers, may include “telematics” systems that monitor information describing the vehicle's location and diagnostic condition. Such telematics systems may include a conventional global positioning system (“GPS”) that receives signals from orbiting satellites and a processor that analyzes these signals to calculate a GPS “fix.” The fix describes the vehicle's location with an accuracy of about 10 meters or better and may include data such as the vehicle's latitude, longitude, altitude, heading, and velocity.
Telematics systems may also include circuitry that monitors the host vehicle's diagnostic system. For example, light-duty automobiles and trucks beginning with model year 1996 may include an on-board diagnostic (“OBD-II”) system as mandated by the Environmental Protection Agency (“EPA”). OBD-II systems may operate under one of the following communication protocols: J1850 VPW (Ford); J1850 VPWM (General Motors); ISO 9141-2 (most Japanese and European vehicles); Keyword 2000 (some Mercedes and Hyundai vehicles); and CAN (a newer protocol used by many vehicles manufactured after 2004).
OBD-II systems monitor the vehicle's electrical, mechanical and emissions systems and generate data such as vehicle speed (“VSS”), engine speed (“RPM”), engine load (“LOAD”), and mass air flow (“MAF”). This data may be processed by a vehicle's engine control unit (“ECU”) to detect malfunctions or deterioration in vehicle performance. In processing such data, the ECU may generate diagnostic trouble codes (“DTCs”), which are 5-digit codes (e.g., “P0001”) indicating electrical or mechanical problems with the vehicle. Most vehicles manufactured after 1996 make the information available through a standardized, serial 16-cavity connector located in the vehicle and referred to herein as an “OBD-II connector.” The OBD-II connector provides a serial interface to the vehicle's ECU and passes data and diagnostic codes to diagnostic equipment located external to the vehicle.
Likewise, heavy-duty trucks may also include a diagnostic system referred to herein as a “truck diagnostic system,” which is analogous to the OBD-II systems present in light-duty vehicles. Truck diagnostic systems may operate under a communication protocol such as J1708/J1587 or J1939 and may include a connector located in the truck's interior and referred to herein as the “truck diagnostic connector.” The truck diagnostic connector, like the OBD-II connector, makes the diagnostic information available to diagnostic equipment located external to the vehicle.