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What the title says, could I use an OBD2 code to control gear shifts in an automatic car? For example send an OBD2 code via a microcomputer like the Raspberry Pi. The car in question is a 2008 BMW e60 530xD.

I know there is something like Service 08 in OBD2, unfortunately it is hard to find specifics and codes for it online. I guess it depends on each car.

I'm asking because I discovered you could use a Raspberry Pi to read OBD2 data from a car like engine load, rpm, pressures etc. All the avaible data could theoretically be used to make shifts in an automatic transmission more optimal. For example when I accelerate from a red light to 50 (kph) in my car it tends to stay in a too low gear for too long, technically increasing fuel consumption and wear. Then on the other hand one could argue that if you accelerated rapidly from 0 to 50 (kph) then you quite possibly might want to continue accelerating in a moment. But since you can read all the data and analyse it then you could take into account how quick the acceleration was. So if it was quick then stay in low gear, else shift up.

  • Some scan tools (read & write ie clear codes) have enough issues trying to just clear codes, so a reliable gear change signal.... – Solar Mike Mar 17 at 13:46
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The commands to read out Speed, RPM and some other sensor data was well as fault codes are standardized for all cars and commonly known. That is, one can "easily" develop some software to read out these, and even to reset fault codes.

But all other functionality like reprogramming/tweaking the ECU are implemented by the manufacturer, and each manufacturer uses his own, proprietary protocol. There might be diagnostics commands to force a gear, but it is possible that the ECU accepts them only under certain conditions. It is even possible that this commands are "password protected", i.e. your software has to log-in before such commands are accepted.

Unless you have access to the confidential documentation about such functionalities, you will not be able to implement them.

On the shifter there is a manual mode where you can push the lever up and down to change gears. Perhaps this signal could be hijacked somehow?

That would be possible. The lever should have sensors for that, and you might be able to simulate the lever e.g. by relays.

  • Thanks for an elaborate answer. Sadly I do not have access to such things. On the shifter there is a manual mode where you can push the lever up and down to change gears. Perhaps this signal could be hijacked somehow? – Tomas Mar 17 at 14:10
  • I will look into that. Thanks. – Tomas Mar 17 at 16:10

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