Confused about OBD II

**tom2112** · 12-17-2003, 10:26 AM

OK. First I read the sticky (thanks Zip-lok) about OBD II, and I thought "Cool! I am all over that." Then I started reading posts in this section about it. And I started to get confused. So I went out to the web (

) to get some answers. Then I became REALLY confused. I even went to the forum for my specific car, and didn't find answers I understood.

I've got a 2003 Mitsubishi Eclipse GT, which I've found has an ISO protocol OBD II interface. Great, right? Well, maybe. So I go to find a cable and software.

It seems the world at large (the net) can't agree on whether you need a cable with built in logic or just a "dumb" cable to connect it to a PC serial port. I've found sites with wiring diagrams for dumb cables and sites selling them. I've also found ones with logic, who's sites declare that you CAN'T use the dumb cables. Which is it? Does it depend on your car? on your software? What?

So I figure I will look at it from the PC to the car side. What software will I run? I'm using WinXP, so it needs to be WinXP compatible. I start looking and I can't find anything that is what I want. All the free ones have crappy interfaces. Autotap is cool, but proprietary (cable) and expensive. Are there alternatives for the "dashboard" style software?

Also there is mention of extended OBD II information that is manufacturer specific. How do I know what it is? Do I want/need it? I do want to get as much info out of the system as I can.

I also want to use the system for engine management down the road. (after modding out my engine) The net resources don't agree on that either. Some say that OBD II is read only - no writing or changing info on the ECU. Some say you can do whole engine maps, some say you can only turn of the check engine light. Which is it?

Damn! I'm one confused PC guy. Sometimes I don't think "car people" speak English.

But I guess they say the same thing about us "computer people".

Thanks in advance to anyone who can clear up some of this stuff for me,
Tom

**_dopehead_** · 12-17-2003, 04:01 PM

Here is what i have figured out :

The cheap solution like the scantool one, which has a small microprocessor in it handles all the ISO/OBD-II communication, comms with the pc is regular 9600 baud serial. This means that this solution is easier to make your own gui for. The Cables without any logic/"cpu" is dependant on your skills at programming a serial port for all sorts of weird stuff like 5 baud and 10400 baud.....not really standard rs232 speeds. However you can make it work with almost any ISO standard of OBD-II, since there is like 4 or 5 different ISO protocols used today.

Extended OBD-II codes are usually hard to come by, since they are manufacturer proprietary. So searching the net or maybe some local dealers will have some info.

You CAN control fuelmaps and other quite interesting stuff through OBD-II, but not in all vehicles. My car is a Citroen Xsara VTS with a Magneti Marelli 1AP ECU, and all vendors of tuning equipment say that it has programmable maps via diagnose plug (meaning OBD-II) One thing though, keep in mind that OBD-II as per the standard has no means of changing any values except clearing DTC's so it must be a proprietary thing again....as with many things in the automotive industry, but you will soon find that out.

Hope this can clear up some things :-)

Jan

**tom2112** · 12-19-2003, 08:07 AM

Thanks a million, Jan. That clears up a lot. So if I understand correctly, I can use whatever cable (logic or not), but I need to get software to match the cable. Also, if I'm going to try to do manufacturer specific stuff, the ones with the generic logic probably won't work. But if I use the non-logic cable, I will probably have to do the programming myself.

That's cool. I did read some stuff about the 5 baud / 10400 baud thing. That doesn't sound like stuff that I want to program. I will probably just go with the scantool cable & software, and see what I can do with it from there. If I need more, I will pick up AutoTap.

Thanks again,
Tom

**00CericaRuss** · 12-19-2003, 01:20 PM

I wonder if there's an software out there for a dumb cable... would be nice

**shotgunefx** · 11-22-2005, 05:05 AM

I know I'm bringing this back from the dead, but while looking for mitsu specific OBDII stuff, this was one of the first results on google. So for posterity, I figured I'd answer this very old question in case someone hits here from google.

My car is a Chrysler Sebring Coupe, built on the same platform as the eclipse. (Basically an eclipse with a longer wheelbase and chrysler designed sheetmetal) All the electronics and mechanical parts are interchangable between the Sebring/Stratus Coupes and the Eclipse.

AFAIK, the P codes are 100% compatible.

I have a list of the trouble codes for the 6G72 and 4G64 here.

**recompiler** · 12-02-2005, 11:36 AM

I have a 2004 eclipse I just bought and I can't find the connector for OBD2! On my old civic it was obvious but the eclipse is taking a little of time to get acustomed to.

**ITL** · 12-02-2005, 11:51 AM

The connector must be located within three feet of the driver and must not require any tools to be revealed. Look under the dash and behind ashtrays.

**recompiler** · 12-02-2005, 12:11 PM

Thanks. I do remmember that thats what the government specified. I checked all the ususal places but still haven't found it. I had the car less then 5 days and need to install the ccarpurt I pulled from my civic and need to connect the OBD2. I checked all the nooks and cranies and still don't see it. I'm sure I missed it. I'll try looking again during lunch. I guess I was hoping someone knew offhand and could say something along the lines of "to the left and jsut below X but to the right of Y".