OBD-II provides access to various pieces of data from the vehicles ECU and offers an invaluable source of information when troubleshooting problems with a vehicle.
The SAE J1979 standard provides definition for the method used in requesting the various diagnostic data together with a list of standard parameters that may be available from the ECU.
The above mentioned parameters are controlled by "parameter identification numbers" or PID's, as defined by J1979.
Vehicle Manufacturers are not required to include all the PID's scheduled in J1979 and are allowed to enhance the system with their own PID's outside the definition of J1979.
The PID data retrieval system and request allows for real time performance diagnostics along with any logged DTC's. |
