The concept is simple. In a modern day automobile, the ECU is sort of a computer which virtually controls every single system. It reads from different sensors like, Inlet air temp, Air flow, fuel temp etc. Based on the input values, it decides on the amount of fuel to be injected, the ignition timing (when that fuel to be burned) etc so that engine burns fuel optimally at all times. In simple terms, ECU read signals from different sensors and based on the readings, fed the engine optimally. It is the sensor values that the ECU reads is what I am interested in. Through a port called the OBDII port or Data Link Locator (DLC) or whatever, we can read the values that ECU reads- realtime. This port is a standard for most of the passenger cars after 1996. OBDII is the protocol used to communicate with this interface. Mitsubishi vehicles uses a proprietary protocol called MUT over OBDII. My car is believed to be using MUTII protocol.
During the operation of vehicle, if the ECU detects any malfunction in any sensor readings, it stores the corresponding error codes in it so that a technician can diagnose it later.
After a bit of googling and understanding the above stuff and some more, I started the search for a cheap option to read data through the DLC. Basically a cable-laptop-software combonation. Cable would connect the laptop with the OBDII port and the software would read and display data. Simple. I came across a software called EVOSCAN (google to get link). There were different cables available, starting from read-only cables to more costly read-write cables.
The cable I needed was OpenPort 1.3D, which is a read-only cable. Ordered one by spending around $67. The cable was to be shipped from NZ. Made a mistake in choosing the cheap shipping option without Tracking. Cable was not delivered. First step is a failure. But everybody falls the first time.
Forgot the entire stuff and one day, the dream of the bond car stuck again. This time decided to try to learn how OBDII interface works. Spent hours reading different forums. Found some interesting links where the circuit designs for the interface cable is available. A Home made MUTII datalogging cable sounds cool. After scouting the WWW for days, I came to understand one thing. Its pure electronics- thats Spanish to me(I am a mechanical engineer destined to work in IT). But then I have learned electronics/electrical more than I have ever learned in my engineering days. I dont fear PCBs anymore.
Some interesting links.
I feel like reading a Text book or a manual of OBDII Scan. Great research and excellent presentation of details explored.
ReplyDeleteCould you please get the cable, read the auto codes and post it.