Hi there,
So, the OBDII connector communicates with the Engine Control Unit (ECU). Depending on the make of the car, the communication is handled on either the J1850 OR IS0 9141 OR CAN buses. I think this statement is right.
But 1. How can I say, it communicates with the ECU only as all buses are multiplexed and ECU might not be the only unit on the bus ?
I have a couple more questions:
2. Via this communication, How can I get any data that is not defined in the OBDII PIDs ? For example, I can get the engine RPM and the vehicle's speed, but what about the status of the vehicle ( Is it moving forward or backward ?) ... How can I get this information ?
3. Since all these OBDII buses are multiplexed buses, so is it valid to sniff any bus ( the CAN bus for example ) in-order to get the information that can't be accessed via the defined OBDII PIDs ? OR Is the data sent on these buses is limited to what is defined by the OBDII standard and that of the manufacturer ?
4. How can I know what the data ( accessible and inaccessible ) that is available from the ECU ?
Notes:
A. These questions might seem a bit overlapped.
B. I'll be posting these questions somewhere else. I hope there is no problem with that on this forum.
Thank you,
Walid F.