De-mystifying DIY OBDII fault code reading and clearing.

De-mystifying DIY OBDII fault code reading
and clearing.

1) Pre requisites - You will need:

a) a Standard Laptop with a USB port (mine's Windows XP, other OS are fine, see Scantool website, download link below).

b) ELM 327 OBD2 CAN-BUS USB Fault code reader

(Search ebay for "ELM327" for results like the one below):

http://cgi.ebay.co.uk/ELM327-USB-OBD2-CAN-BUS-Tool-Interface-Scanner-elm-327_W0QQitemZ320254958166QQihZ011QQcategoryZ30921QQssPageNam eZWDVWQQrdZ1QQcmdZViewItem

Mine came with Scantool software (follow the instructions on the CD's readme.txt to install).

Scantool can also be downloaded free from:

 http://scantool.net/?mode=displaySoftware&software_id=39&category=ScanTool.net

This guide will show you how to use Scantool, although similar software is probably just as easy to use.

 

2) Locate your ODB socket cover (here on a UK RHD 2001 325Ci)

Place your finger where the red dot is and flick the flap down to reveal your OBD2 socket.

You'll note from the insert that the plug is keyed (squared off corners at one end). This is the way to insert your plug.

With laptop running and ignition off, connect ELM 327 to laptop and car.

3) Turn key to make ignition live and start Scantool software.

Scantool will detect the car (You will see lights flicker on the ELM 327 box indicating communication).

 The main menu then comes up like this:

4) Click on "Read Codes". "MIL is ON" indicates your engine light is notifying you of a fault.

Your OBD2 Fault Code will be displayed.

You can look up more info about your fault here:

http://forum.e46fanatics.com/showthread.php?t=303141

In my case it was "P0420 Catalyst System Efficiency Below Threshold (Bank 1)".

(I suspect the problem may be the bank 1 post-cat O2 lambda sensor, as the car has since passed an MOT with emission test, so the cats must be doing their job).

5) Having made a note of of your Diagnostic Trouble Code and definition, Click on "Clear" to clear the fault.

Click "Yes" on the confirmation screen.

Your MIL (engine fault light) is now OFF, you no longer have any DTCs (Fault codes).

6) Start the engine, confirming this is true. Click on "Main Menu"

7) With the engine running, click on "Sensor Data".

You will notice "Fuel System Status" at the bottom of the page
is "Open Loop".

It will stay "Open Loop" for a few minutes while the engine / sensors warm up.

In the "Open Loop" state, the sensors / emission controls are not yet working.

You'll also notice the high RPM when idling during warming up.

In a few moments when the engine / sensors have warmed up the "Fuel System Status" will go "Closed Loop".

This indicates the O2 lambda sensors are now operating.

If your MIL (Fault light) hasn't come back on then all seems well.

Clicking "Next" through to page 3 displays readings from your O2 lambda sensors.

There are several other pages giving more information including engine temp and air temp.

You can now switch off the ignition and disconnect the ELM 327. It takes a few minutes and you're done.

There is lots of conflicting information regarding how to interpret O2 sensor readings.

I found this site most informative:

http://www.lambdapower.co.uk/TechNotes/technotes_index.asp

(Disclaimer: I make no guarantees about this process, just that it works for me.)

HOLY SHIET DUDE! i'd love to have this for my car. it'd be a lot easier than buying/renting an obdII fault code reader.

I'm guessing this works for any obdII car?

The only thing i'm wondering about is that since i'm in the US will i still be able to use that software n stuff?

great find man.

Wow, this has been on my mind for some time. I'm glad that people are just as interested in this as I am. The open source/free aspect I mean.

I'm buying one of those devices off eBay ASAP. There's lots of Linux apps already for this. Great stuff. Sticky this post.

Yes, this will work for USA cars. OBD II is a standard for a reason.

I just bought a Bluetooth one off eBay (woooo go China...). I'll be sure to report back after trying it out.

Originally Posted by SL Blak Soldier

I'm guessing this works for any obdII car?

Yes, I've used it to clear codes on my friend's Merc C200 Kompressor.
Now he's bought one too.

Originally Posted by SL Blak Soldier

since i'm in the US will i still be able to use that software n stuff?

I should think so, all the software seems international.

Originally Posted by SL Blak Soldier

HOLY SHIET DUDE! i'd love to have this for my car. it'd be a lot easier than buying/renting an obdII fault code reader.

I'm guessing this works for any obdII car?

The only thing i'm wondering about is that since i'm in the US will i still be able to use that software n stuff?

great find man.

Since 1996 the OBD-II specification is made mandatory for all cars sold in the United States.

From this year all cars sold in the United States are required to use the ISO 15765-4 signaling standard (a variant of the Controller Area Network (CAN) bus.

Originally Posted by mooninite

I just bought a Bluetooth one off eBay (woooo go China...). I'll be sure to report back after trying it out.

I will wait for your reply, I'm thinking of buyng one for myself.

Can this thing program your LCM?

Originally Posted by Atlas

Can this thing program your LCM?

Why would it? This is OBD code reading. Not any sort of programming.

OK, my reader arrived today. It works! I was able to read all sorts of miscellaneous information. I had no trouble codes either. Yay.

I'll post pictures, etc. later. Feel free to ask me questions.

Originally Posted by mooninite

OK, my reader arrived today. It works! I was able to read all sorts of miscellaneous information. I had no trouble codes either. Yay.

I'll post pictures, etc. later. Feel free to ask me questions.

Which software are you using and can you get real time data?

Originally Posted by Hacko

Which software are you using and can you get real time data?

I've used software for both Linux and Windows so far, and both work. It seems any "ELM327 compatible" software will work with it.

http://www.scan-tool.net It has a windows/linux client, works great, but refresh doesn't work 100% of the time on Vista.

http://sourceforge.net/projects/garmon Has same capabilities of Scan-Tool, but it is programmed to use native Linux graphical toolkits, so it looks much nicer.

Bluetooth was the way to go. Of course, now I need to buy an Asus eeePC 901 to go with it (with Linux, of course).

Originally Posted by Hacko

Which software are you using and can you get real time data?

Using scantool (with Win XP) in my screenshots above, the data is live and displayed constantly changing. There may be a slight lag (it's hard to tell), but certainly when I push the accelerator down a little you can see the rpm figure increase in real time.

Originally Posted by mooninite

I've used software for both Linux and Windows so far, and both work. It seems any "ELM327 compatible" software will work with it.

http://www.scan-tool.net It has a windows/linux client, works great, but refresh doesn't work 100% of the time on Vista.

http://sourceforge.net/projects/garmon Has same capabilities of Scan-Tool, but it is programmed to use native Linux graphical toolkits, so it looks much nicer.

Bluetooth was the way to go. Of course, now I need to buy an Asus eeePC 901 to go with it (with Linux, of course).

Well done, I'll be interested to hear how well other software works. I've tried a couple of other windows utilities (can't remember details right now, I had them on the laptop) 1 worked but I just preferred the simplicity of the Scantool layout, 1 promised to do even more but I couIdn't get it to work with the ELM327 USB box as the USB port is created as Com6 and infuriatingly the software will only let you choose Com1 or Com2. I tried a port mapping utility but that didn't work.

I don't have Linux on the laptop at the moment so won't be testing linux apps hooked up to the car, though I do have Linux on my dual boot PC (Fedora core 7) and on PCs at work (Scientific Linux 4).

On my laptop I have Vista, I hate it but it is what I have.
1. Does this ELM327 USB OBD2 CAN-BUS Tool Interface Scanner work with Vista?
2. Does the ELM327 just plug up, install needed software from CD, then it works, or do I need to download a patch for Vista compatibility?

Originally Posted by BMW_SSG

On my laptop I have Vista, I hate it but it is what I have.
1. Does this ELM327 USB OBD2 CAN-BUS Tool Interface Scanner work with Vista?
2. Does the ELM327 just plug up, install needed software from CD, then it works, or do I need to download a patch for Vista compatibility?

Check the specifics of the software packaged with the model you buy with the seller, but yes, mine does just work with Vista. Tested it on my girlfriend's HP laptop.

Sweet, thanks for the info!!

this is nice! but there was another thread that someone found something a little more pricey and it allows u to do options like drl, lcm, etc.. its about $100 shipped so far the elm has been tested and it works for check engine lights, clearing codes, and reading codes the other hasnt been tested yet...

Originally Posted by chnzgoofball

this is nice! but there was another thread that someone found something a little more pricey and it allows u to do options like drl, lcm, etc.. its about $100 shipped so far the elm has been tested and it works for check engine lights, clearing codes, and reading codes the other hasnt been tested yet...

I'm guessing what you're paying for is the software. The ELM or any other hardware is essentially just a serial interface between your laptop and your car. What the ELM327 USB also does is act as a serial to USB convertor as modern laptops no longer have serial ports.

If anyone can get hold of the software that supports these extra functions, (if it is able to communicate using Com port 6, the virtual com port the USB driver install stuff sets up) I'd imagine it would work through an ELM.

The only "do all" software that I've seen so far, (I have a thing called BMW Scan) although it claims to be fully functional, was "legacy" software, designed for a pre-USB era when PCs and laptops had a couple real serial ports (RS-232), and only knows about options of Com1 or Com2 to be selected for connection.

I believe that's why the interface boxes I've seen are supplied with the do-all software don't seem to have USB connectors, but the older D9 RS-232 connectors.

I've tried port mapper software to map virtual Com port 6 to Com1 or Com2 but that didn't work.

Now if I can work out how to set the USB ELM interface to install as port Com1 or Com2 on my laptop, we could be in business.

I read your post and went ahead and bought the unit. After hooking it up and it does see my laptop with the car on but I get an error "protocol not found"
I have a 2000 323Ci, any ideas?