Beginner questions

Hello, I am new to Realdash and have some ‘noob’ questions; sorry if they seem somewhat stupid or are already explained elsewhere.

First of all, I’ve been reading quite a lot and am impressed with what Realdash can do, thanks for all the coding work!

I recently somewhat resurrected a 1998 VW Passat Variant, 1900 TDI. Problems with a driveshaft, with the clutch, and some other, less important issues with electric windows and door locks were fixed/replaced (I didn’t do all work myself, but as much as I could).

The dash isn’t in great shape; the needles for rpm and fuel level move but are in completely the wrong spot, and the display doesn’t work. I was told replacing it requires you to somehow enter a pin code, to ‘learn’ it to the ECU, but I wouldn’t know how to and I expect the OEM part to be quite expensive anyway. As the regulatory ‘noose’ tightens for old cars (next year I won’t be allowed to drive it in the whole south part of Belgium, for example, unless I pay a daily fee of €30 or sth like that), the plan for now is to keep everyting on a tight budget.
Also, working on the dash is a bit of a pain.

Enter Realdash. I have a cheapo bluetooth OBD2 connector (Vgate Scan I believe, a common semi-transparent blue one) which I used to read error codes on my previous car, and the Android app shows things like speed and rpm correctly. I haven’t been able to get fuel level though, I tried changing the source input for fuel level to “ECU Specific->OBD2: Fuel Level” as explained elsewhere on this forum, but no result yet. Maybe it has to do with how I add a custom dial, dunno (is there a ‘theme’ that has fuel level reporting? might be a good way to test).

How can I check which values my car outputs via obd2? Can I do this using Realdash, or is another piece of software needed? In that case, command line stuff isn’t an issue.
Great to see that there’s a linux version available, by the way!

I know about OBD2 being not ideal for real time stuff, it is for diagnostics after all, but for now some lag is acceptable to me; I’ve been reading about the CAN ‘route’ though, available hardware, splitter cables, whatever. Interesting stuff! But that’s for later (unless I might be able to read the fuel level that way, and not via OBD, no idea)

Also, generally speaking, is it possible to read CAN or OBD data with a (cabled) connection made elsewhere in the car, like somewhere under the dash maybe? My OBD connector is next to me, behind the hand brake, not impossible to route cables from there but it’s not very convenient, for now it’s not a problem as I use bluetooth but as a general thing I prefer wired over wireless…

Thanks in advance for any reply!

1 Like

In RealDash OBD2 connection settings, there is an option ‘OBD2 Monitor’ which allows you to enter any commands to your vehicle and inspect the responses. This should help you to analyze what data your vehicle is sending.

Regarding fuel level, see this post:

OBD2 indicators, fuel level and gear - Connectivity / OBD2 - RealDash Forum

You can purchase an OBD2 extension cable and use USB version of the OBD2 adapter. See recommended adapters here:

What Adapter shoud I use? - Connectivity / OBD2 - RealDash Forum

1 Like

Thanks for your reply! I’ll probably look into things later today, gotta do basic maintenace first now as the oil is quite old (and there’s too much in it…).

I found more info on the protocol and which commands to send / how to understand the replies, so that should work, i’m quite curious actually.

So, I checked out the shell, I had no idea it would request the available pids after setting up the connection, that’s quite convenient. I took a picture of the output.

No luck for the fuel level though, it’s not supported over OBD2.

I’ve been reading quite a lot and if I’m not mistaken the protocol used by the Passat 3B5 is ‘KWP-1281’, a proprietary VW one. Will this cause problems? Do I need a specific adapter for it?

The Ross-Tech software is apparently still popular for VAG cars, and OBDEleven seems to be the new kid on the block. If I understand things correctly, they are mainly interesting if you want to change things, e.g. enable/disable certain features?

Typically OBD2 Monitor detects the protocol and no other protocol produces any results. All data probably is available from the OBD2, but would require using VAG specific PIDs with custom XML description file.

1 Like

The VAG specific pids is something I should still look into indeed, I’m curious if more will be available.

I can see if I can somehow scan for them, however I read this post by ‘Uwe’, I think that’s Uwe Ross of Ross-Tech?