I try to build an ARDUINO electronic item for displaying working datas of the car (Lada Kalina2 VAZ 21925), for example outdoor ambient temp, fuel level, coolant temp, etc. There is a BOSCH Motronic PLC built to the car.
I wrote (copy/paste/edit) a sketch, I tested in my "service table" with an ELM327 module (so far away from the car...), it seems, that the connection created.
Pls check my sketch and inform me, is it safe for the car's controller? Is it sure, that I can't injure controller or modify any essential parameter? I'd like ONLY reading PID values.
I don't see any threat of accidentally changing any calibration parameters or flash contents through an ELM327 OBD interface. You're asking for specific PIDs; that's pretty safe.
I think you already received your answer, but i wanted to add a little more, just for the sake of contributing.
if you are only looking to read CAN data such as generic OBD PIDs or even manufacturer specific PIDs by sending the appropriate CAN message with the header 7DF, then there is no risk of modifying anything. for instance if you send 7DF 02 01 05 xx xx xx xx xx that is asking the ECM for Mode 1 PID 5 which is "current data" and "Coolant temperature. if your ECM supports coolant temp you will get a reply most likely from 7E0 with 03 41 05 NN xx xx xx xx xx (the NN being the hex data you want)
like the other person said, there is little chance of causing any harm by sending message requests to the ECM. worse case the ECM does not respond or you get a response from ID 484 or similar with garbage data in it which means the module you requested a response from does not recognize the request.
