OBD2 Question re cables and pinouts

[lifestyler]

Hi all,

I have been doing heaps of research re OBD2 and I keep coming across conflicting information.

For example; using software from obd-2.com, some people say you can hook your laptop directly to your OBD2 connector under the dash using a simple serial cable (found this on this board on a thread) while others say you need a piece of hardware in-between to convert 5v from the laptop to 12v on the truck.

From my searching on the Internet, I found pin connections to connect a DB9 connector on the back of a laptop to an ISO OBD2 connector. The pin connections are:

Laptop (DB9) (Truck) ISO 16 Pin D Type Connector

1-----------------------5
2-----------------------4
3-----------------------6
4-----------------------7
5-----------------------14
6-----------------------10
7-----------------------2
8-----------------------15
9-----------------------16

Using these connections, I can rig up a serial cable in 1/2 hour, however I was wondering if anyone has actually done something like this or do I need to get a piece of hardware as some people state.

The reason I'm asking is that I don't want to fry anything

Cheers and TIA

Erron

 

[robertofollia]

Chris is the OBD2 and everything-disco-related guru and expert. He can guide you best.
The only thing I can tell you is that OBD2 readers work, retrieve and erase codes, as I did in my Euro-spec 1999D2.

Good luck
Robert

 

[p m]

FWIW - the OBD-2.com gadget does have a little PCB inside with one or two chips, and a few other components.

 

[lifestyler]

Thanks for that

p m: hmmm, it does sound like there is a converter in there of some kind. I think I'll play it safe and just buy it off obd-2.com

Thanks again.

Cheers

Erron

 

[p m]

fucking 5-button mouse, just killed all I wrote...

There's a chip that interfaces OBD-2 connections to RS232 - check the web.
Also, I doubt OBD-2 output signals would go beyond +12VDC, so you could use RTS/DTR etc. inputs of the COM port if you knew the OBD-2 data exchange protocol. It would be a direct connection (may need a diode or two), and a piece of software to make it work.

 

[vabiro]

Erron,

There is a ton of info at http://www.scantool.net/products/index.htm, including PCB layouts, parts lists, and info in the RS-232 to ODBII cable. They also have free software and a Forum

Hope this helps,
Victor

 

[craig]

I'm updating the scantool.net software to include the Land Rover proprietary code definitions. In fact, I should stop procrastinating and update it tonight. When it's done, I'll put it up for download on www.soggyoval.org (no registration will be required to download).

--Craig

 

[lifestyler]

Thanks pm, vabiro and craig

One thing I like about some software is the ability to graph o2 levels etc - especially while you drive. If I use software from say obd-2.com to do this, can I purchase your components and use them with the obd-2.com software Craig?

Cheers

Erron

 

[craig]

Nope, you cannot use scantool.net software or the ELM hardware interface with the obd-2.com software. They are completely different systems, and completely unrelated to each other.

obd-2.com uses a proprietry hardware solution and proprietary software. The obd2.com software includes many definitions/explanations of Diagnostic Trouble Codes (DTCs) that are specific to Land Rovers.

Scantool.net makes an open hardware platform called "Elm Scan" that can be used with a whole bunch of free and/or commercial software. One of the free pieces of software is from the people that run the scantool.net website and is aptly named, "ScanTool".

This is an open source piece of software. It isn't very full featured in terms of graphing, logging, etc. Because it is open source, I am adding all the Land Rover specific definitions and proprietary DTCs that Disco2.com had listed on their website. This is the same list as I have up on soggyoval.org in our tech section now. I'm just going to integrate it into the scantool.net software.

The scantool.net software does 3 things quite well though: 1. It can be used to reset your Check Engine light, and 2. it has big buttons which work well on a touch screen, 3. it has the potential to talk to the SLABS with a little bit more reverse engineering and coding. Note that 3 is possible because it is open source.

 

[Chris-St Louis]

Hi all,

I have been doing heaps of research re OBD2 and I keep coming across conflicting information.

For example; using software from obd-2.com, some people say you can hook your laptop directly to your OBD2 connector under the dash using a simple serial cable (found this on this board on a thread) while others say you need a piece of hardware in-between to convert 5v from the laptop to 12v on the truck.

From my searching on the Internet, I found pin connections to connect a DB9 connector on the back of a laptop to an ISO OBD2 connector. The pin connections are:

Laptop (DB9) (Truck) ISO 16 Pin D Type Connector

1-----------------------5
2-----------------------4
3-----------------------6
4-----------------------7
5-----------------------14
6-----------------------10
7-----------------------2
8-----------------------15
9-----------------------16

Using these connections, I can rig up a serial cable in 1/2 hour, however I was wondering if anyone has actually done something like this or do I need to get a piece of hardware as some people state.

The reason I'm asking is that I don't want to fry anything

Cheers and TIA

Erron

http://www.obdiicsu.com/Docs/LinkConnectors/SAEConnector_files/SAEConnector.asp

Check this site.... Does it help?

http://obd2cables.com/products/

Check this one too.

 

[vabiro]

 

[p m]

Here's PC RS232 DB-9 pinout: http://www.aggsoft.com/rs232-pinout-cable/serial-port-db9.htm

Pin Name Direction Description
1 CD ?? Carrier Detect
2 RXD ?? Receive Data
3 TXD ?? Transmit Data
4 DTR ?? Data Terminal Ready
5 GND System Ground
6 DSR ?? Data Set Ready
7 RTS ?? Request to Send
8 CTS ?? Clear to Send
9 RI ?? Ring Indicator

Looking at the cable diagram, I think this is _not_ the cable to connect the OBD-2 to a PC COM port (that is, you are unlikely to talk to your ECU using Hyperterminal), OR you need a special software to make use of DTR/DSR/RTS/CTS lines.

 

[craig]

From what I learned a while back:

1. You will fry your serial port if you connect it directly to the OBD2 connector.
2. Once connected with the appropriate cable you will need to send a specific escape sequence to get the port to talk to you.
3. The OBD2 connector is very dependendant on timing. If your laptop/pda is busy doing something else it will not be able to respond fast enough to keep the communication working properly.

The ELM interface, and other aftermarket interfaces handle all of these problems for you. You can then talk to the OBD2 port with hyperterminal, aftermarket software, or your own software as if it is just a serial port. The ELM interface even uses Hayes AT commands to control the ELM.

--Craig

 

[lifestyler]

Hi All,

Thanks for all the info.

After reading just about everything, I think I'll just go to obd-2.com and order his solution with the hardware doover-lacky

I'll order the autologic solution next year

Cheers

Erron