[b3lha]

Originally Posted by SVXdc

I'll second Jim's comments.

It would probably be smarter to keep the TTL level signals as short as possible — as close as possible to the ECU. In other words, the MAX232 chip circuit should be right at the ECU plug.

Even if you leave your adapter box as-is, shielded TTL and RS-232 cables may help (if they're not already).

You may be getting additional noise if your laptop is connected to a different power and ground than the ECU (are you using the cigarette lighter jack, perhaps?).

It may be worth trying to clean up the power for the MAX232 chip. Perhaps driving it from a separate battery rather than from the car's battery.

Originally Posted by SVXdc

So that USB-to-TTL adaptor (where the chip is inside the USB plug and the long wire is TTL) may not be such a good idea. However, one of the companies has this version that is a USB socket on a little PC board with the tiny chip right underneath it...

(img)

That could be attached to the ECU plug, with a USB A-to-B cable to connect to the laptop.

That's a cool little device. Looks like it could be installed in the dashboard somewhere. I had no idea all these things existed.