If you have read the article about OBD-II, then you are off to a great start! This article will be looking at the communication process between a scan tool and your vehicle. There are two important things that we will look at: PIDs and the modes.
First, we will take a look at PIDs. PID stands for Parameter ID, and it is the code that requests the information from your vehicle. There are many standard PIDs, but each manufacturer has their own PIDs that are specific to the make and model. This means that some information can be obtained from certain vehicles, but not from others.
As mentioned above, the other important part of the communication process is the mode of operation. There are 10 modes, and each mode is responsible for communicating a certain type of information. For example, mode 1 is for current or live data. From mode 1 you can obtain information like the current fuel trim, engine RPM, and engine coolant temperature. Those are just some examples of the information that you can obtain. Within mode 1, you will need to enter a PID to get the exact information that you are looking for.
For a closer look at the other modes, lets look at mode 2. Mode 2 is responsible the for the freeze frame data, which is a snapshot of the current data. It is very similar to mode 1, but it is a picture rather than live data. Mode 3 shows stored DTCs, while mode 7 shows pending DTCs and mode 0A shows permanent DTCs.
All of this information is great to have to get a good idea about the health of your vehicle, but to reiterate, not all vehicles are the same. Before 2008, there were multiple protocols that vehicles used. Some examples of the different protocols are VPW, KWP, and ISO. Not all modes are supported on the different protocols. Starting in 2008 CAN became standard, which has made the communication process a little easier. The various protocols used along with the non-standard PIDs means that some information is tricky to get at without the information that is kept private by the manufacturers. Hopefully with the trend of making more of this process standardized, and the improvements made to scan tools, vehicles will be even easier to understand!
We hope this look into the communication process helps you understand your vehicle even more! Be sure to come back to "Learn with us!" to get more valuable information about your vehicle!