OBD MPGuino gauge - Page 34 - Fuel Economy, Hypermiling, EcoModding News and Forum

Mothinator · 03-08-2009, 02:37 PM

Hi everyone,

I have a '03 Hyundai Elantra which I believe is ISO (OBD pins 4,5,7,8,12,14,16 are populated). I haven't been able to find a definitive source to tell me it is ISO though.

Anyway, I built the ISO interface to the specifications on the google code page. However, when I plug it in, I get an ISO9141 init failed error. I'm using v125 of the code. I've checked the connections and the all seem to be fine.

Is there anyway to determine if this is a problem with the chip or with the car? Are there parameters in the code that may need to be changed?

I'm new to microelectronics (this is only my second project), so its possible I'm missing something obvious.

Thanks for your help.

Magister · 03-09-2009, 09:06 AM

Yes 03 Elantra should be ISO, I can not test ISO as my car is CAN, I know some people in this thread are using an ISO version, for those people : please post the mod you did to the hardware or software to make it works, thanks you

electromike · 03-09-2009, 05:23 PM

Version 125 is what I am running in my car right now. And it works fine. I have a 1997 Honda Civic that is also ISO.

I would double check the connections on the MC33290.

Also, on my civic, the unit will not init if the car is not running (the ECU off when the car is off, thus no communication can take place)

And finally, if it says failed init... it isn't really trying again. I think there is a bug there that is still to be worked out...

Mothinator · 03-19-2009, 11:52 PM

Hi Everyone,

I tried reseating the connections and still didn't work. I have the whole thing on a solderless breadboard and I want to get it to work there before I solder it up.

So a novice question: On the diagram for the ISO interface there appear to be two grounds. One from pin 1 and the other from pin 2 on the DB9.

It shows them as not being connected to one another. Is this correct? It seems to me that they should be connected because I don't see how the MC33290 could transmit to the arduino without it knowing the arduino ground level.

Thanks for your help!

Magister · 03-20-2009, 08:39 AM

They sould be connected in the car plug anyway, there are the "signal ground" and the "ground" but they are the same, you can connect them together.

dcb · 03-20-2009, 11:59 AM

Does anyone know what the iso 9141 L-line is for? It says (otpional) and isn't in the obduino diagram, but I am wondering if it is optional from a vehicle manufacturers perspective as I see it connected on other obd products. I'm looking at a "couple transisters" ISO 9141 add on for a guino so will look into iso 9141 a bit more.

Per here for initialization :Second article for Evaluation Engineering

The tester sends 51 at 5 baud on both the K- and L-lines. Once completed, the L-line is disabled and idles in the high state.

The vehicle computer(s) wake up, but only the computer responsible for diagnostics answers with 85 at 10.4 kb/s. This is the synchronization byte.

All subsequent communications occur at 10.4 kb/s.

The vehicle computer sends Keyword #1, a 1-byte value.

The vehicle computer sends Keyword #2, a 1-byte value.

Keywords are sent seven data bits with one odd parity bit.

The tester acknowledges by sending the logic bit-wise inversion of Keyword #2.

The vehicle computer acknowledges by sending the logic bit-wise inversion of the wake-up address (that the tester sent in step 1).

At this point, the communications link is initialized and operational.

Once the link is initialized, it must be maintained. If there is no message traffic on the link for 5 s, each computer assumes communications are over. The initialization sequence must be repeated to re-establish the link. The tester may periodically transmit a keep-alive message to maintain the link.

Magister · 03-20-2009, 12:24 PM

L line was rarely used, and only at the beginning of OBD2, I found a list somewhere of vehicle using L line and it was only a few.

dcb · 03-20-2009, 05:21 PM

I didn't find anything conclusive but it does suggest on obddiag.net that he doesn't think any US cars ever had l-line. I won't sweat it for now.

P.S. I really like the "send 0x33 at 5 baud" bit in the code, I wondered how you were going to do that

llamacheez · 03-25-2009, 10:52 AM

Hi guys, I'm going to overreach in asking for help so forgive me in advance

. I drive a 2008 Civic and would like to build an OBDuino for it. I have looked through this thread and the opengauge wiki, but while I know how to solder and all I think I'd be more comfortable if I had like a list of instructions, do you know what I mean?

Also I was thinking about getting this arduino kit: Freeduino USB complete KIT (Arduino Duemilanove Compatible). Does that look alright?

Thanks guys, sorry to be a bore....

Edit: I believe my car has CAN. I think this because of (Wikipedia: ) "2008: All cars sold in the United States are required to use the ISO 15765-4 [3] signaling standard (a variant of the Controller Area Network (CAN) bus)."

vlarcjj · 03-26-2009, 07:32 AM

Hi Magister,
I'm very interested in the new version of the board using the MCP2515 you've been working on. I've browsed the google code repository and I did not see there the code you use for this version of the board. Would you mind sharing it even if it's still an early draft?
Thanks in advance.