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Car diagnostics with BS2 — Parallax Forums

Car diagnostics with BS2

achilles03achilles03 Posts: 247
edited 2005-01-07 16:22 in BASIC Stamp
Has anyone here attempted putting together something to do car diagnostics with the BS2?· From what I see, it looks like all you'd need would be an LCD, the proper connector, and the specs for the interface.

Dave

Comments

  • The Lazy DestroyerThe Lazy Destroyer Posts: 21
    edited 2004-12-20 05:51
    This is kind of like the project I am doing right now, using a 2p40.

    So far it's incorporating a LCD "guage cluster" of sorts displaying O2 count readings (averaged for accuracy), RPMs, fuel pressure, vacuum/boost, and quite a few temp readings of various parts. Wiring has become pretty intense though.

    I also plan on having another system to control the tranny, including shift points, manual electronic shifting, torque converter setpoints, etc., but I have not quite dived into that yet as I am still pretty busy getting everything worked out with the LCD display stuff. Last step is engine control, but at the point I am unsure if a Stamp would be best.

    Or are you referring to something like datalogging using the car's existing hardware?

    -Blake
  • achilles03achilles03 Posts: 247
    edited 2004-12-20 11:28
    The Lazy Destroyer said...
    This is kind of like the project I am doing right now, using a 2p40.

    So far it's incorporating a LCD "guage cluster" of sorts displaying O2 count readings (averaged for accuracy), RPMs, fuel pressure, vacuum/boost, and quite a few temp readings of various parts. Wiring has become pretty intense though.

    I also plan on having another system to control the tranny, including shift points, manual electronic shifting, torque converter setpoints, etc., but I have not quite dived into that yet as I am still pretty busy getting everything worked out with the LCD display stuff. Last step is engine control, but at the point I am unsure if a Stamp would be best.

    Or are you referring to something like datalogging using the car's existing hardware?

    -Blake
    Yeah, like datalogging or just running diagnostics.· I took my wife's car in to Autozone the other day to get a "check engine" light checked out, and realized it might not be too hard to get a BS2 to do similar functions that their handheld diagnostic unit was doing.· Do you know what protocol or interface·cars use?· Is it an industry standard, or does it vary a lot from car to car?

    Thanks,
    Dave
  • steve_bsteve_b Posts: 1,563
    edited 2004-12-20 12:07
    There was another thread on this ("Auto Diagnostic" or something near that).

    You're definately not the first person to think about it....nor the last.

    I'm planning on using this as my latest "big project" (just been itching for something to do).

    The easiest part of your first post to get is the connector and the LCD....try and find the spec on the Net, for FREE that is.
    Nobody seems to have posted the protocol in detail.· All I've found is that Gm is something like PWM and Ford is Variable PWM....and the ISO (Eurpean) wasn't stated.

    I had to order a book with the protocol (a few $'s) but looks like I won't get it in time for Christmas, ah well.· I was hoping to take the book to the parents while on break, but I hope to get in to it after new years and post results here.· OF course, having said that, do feel free to dive in and crosspost your results as well.· I don't intend to dissuade others from doing it.



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    ·

    Steve
    http://members.rogers.com/steve.brady
    http://www.geocities.com/paulsopenstage

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • Larry~Larry~ Posts: 242
    edited 2004-12-20 17:08
    I had to order a book with the protocol

    What book did you order and what protocol was it for
  • steve_bsteve_b Posts: 1,563
    edited 2004-12-20 17:54
    AH...yer gonna make me use my mind aren't ya....



    Uhm....I grabbed it off of Amazon.com

    Here's the link:

    http://www.amazon.com/exec/obidos/tg/detail/-/0971541140/104-6877387-6887105?%5Fencoding=UTF8&v=glance

    ·I saw a reference to this particular book off of a website (can't remember which one...) and it doesn't look too bad.· Definately cheaper than the protocol specs from the standards guys!

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    ·

    Steve
    http://members.rogers.com/steve.brady
    http://www.geocities.com/paulsopenstage

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • The Lazy DestroyerThe Lazy Destroyer Posts: 21
    edited 2004-12-21 00:37
    Man do I hate OBDII tongue.gif

    Achilles, what year is your wifes car? From my experience from modding cars, OBDII stuff (usually around '96 cars and up) is always more of a pain in the Smile than OBDI, and the equipment is usually a difference of night and day as far as cost goes, like the scanners places like Autozone use. In fact, OBDII to OBDI swaps are pretty common to keep costs down. But I dont have any real experience with it as far as trying to interface with it, but have heard it is no walk in the park.

    Steve, let us know how that book is, I have also wanted to figure out how to interact with the PCM, but havent quite gotten there yet!!

    Post Edited (The Lazy Destroyer) : 12/21/2004 12:40:20 AM GMT
  • Larry~Larry~ Posts: 242
    edited 2004-12-21 01:23
    Here is some OBDII protocol stuff I just downloaded
    Not sure what is here yet but it looks like some good data.

    Larry Gaminde
    pdf
    pdf
    eady-157.pdf
    1M
  • achilles03achilles03 Posts: 247
    edited 2004-12-21 14:04
    Thanks guys... my wife's car is a 98' Corolla, and I have an '03 Accord. It'd just be nice to have something to determine if the "check engine" light is due to a minor problem, or something that might make the car explode if you keep driving it. When we took it to Auto Zone for a free diagnosis, it turned out the "check engine" light was due to low catalytic converter efficiency, which might have just been due to coolant temperature. We cleared the error, and it hasn't popped up since.

    It'd also be cool in a geeky sort of way if you could datalog drives for your car...
  • steve_bsteve_b Posts: 1,563
    edited 2004-12-21 15:32
    I have a 2002 Jeep TJ....and a neat little fuction for diagnostics is that my digital Odometer readout will display any error codes to me.
    And, if I'm not mistaken, it will give a brief description....or just a label along with the code (I'M NOT SURE ABOUT THIS ONE...might just be the newer NEW cars!).

    Anyhow, with your vehicle off....insert key and turn to the on position (do not start the engine though), do this 3 times; So it's on-off; on-off; on-off.
    Then 'on' the last time and you should get some gauge checks and lamp checks and then it should spit out your trouble code on that little digital odometer display.

    This will LIKELY work on your newer vehicle....might not on the '98.· Then again, this might be a "BIG 3" thing and not a foriegn thing....
    Anyhow, it works on north american vehicles for sure!



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    ·

    Steve
    http://members.rogers.com/steve.brady
    http://www.geocities.com/paulsopenstage

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • steve_bsteve_b Posts: 1,563
    edited 2004-12-21 16:11
    I'm just looking at the standard that Larry Gaminde posted....



    It is dated June of '93 as a submission for recognition as a Standard....I don't know if this means it became standard...but since I haven't been able to find current standards on the net, I'll assume that it was reworked somehow.· But maybe not....

    Anyhow, at the least it gives an idea how it might work.....

    Thanks Larry

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    ·

    Steve
    http://members.rogers.com/steve.brady
    http://www.geocities.com/paulsopenstage

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • m_fabio2m_fabio2 Posts: 49
    edited 2004-12-22 19:28
    The on/off only works with a OBD I computer. Anything newer, you need to interface with the computer itself in order to get the codes.
    Some threads ago I saw a chip that would act as a interface between a OBD and a Stamp. I think the cost was in the neighboor hood of $35. I realize the stamp can easily handle the chip does, but the cost in memory might enough to sacrifice your LCD screen.
    I'll add the website for the chip when I get home.
  • steve_bsteve_b Posts: 1,563
    edited 2004-12-22 19:58
    Well, you got me thinking....
    I was under the standing that '98 and newer were all OBD2.
    and my Jeep is a 2002 and DOES work with the on-off trick.

    Then I do a quick search and the first site says, "for ODB1 vehicles do the on-off trick <paraphrasing>....and counting the blinkety blinks!"
    Anyhow, I couldn't find anything that directly said mine was an OBD2....but certainly this guy < http://www.stu-offroad.com/misc/obdii.htm·> has a '98 TJ with OBD2.· No reference to the on-off thing.

    He used this product from these guys: http://obddiagnostics.com/
    This site sells the BR16Fxx IC for interfacing between a laptop and the car computer.· Good site actually,

    I've included a couple other pages off this site.·

    And certainly after 1996/1998 most vehicles went to OBD2.· So, I'm certain this on-off trick that I'm doing is being done on an OBD2 vehicle.

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    ·

    Steve
    http://members.rogers.com/steve.brady
    http://www.geocities.com/paulsopenstage

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
    pdf
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    BR16F84 OBD2 interface IC.pdf
    130K
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    circNotes.txt
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    pwmmode1_TXT.txt
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  • m_fabio2m_fabio2 Posts: 49
    edited 2004-12-23 01:51
    Going back through the old posts, I found this website,

    http://www.elmelectronics.com/obdindex.html

    One of the chips converts OBD II to RS232, which is very usefull.
  • steve_bsteve_b Posts: 1,563
    edited 2005-01-05 02:45
    Well, today i took delivery of a couple of ELM322 IC's that convert ODB2 (Variable Pulse Width) to RS232.

    I've also picked up a book off of Amazon.com to help a little (It's not the ISO/SAE protocol descriptions).

    The ELM datasheet gives enough information to get the generic trouble codes and decode them easily enough.· It'll take a bit more work to get the manufacturer specific codes....just a different register to look in on the car computer!



    Anyhow, I hope to get the circuit punched together this week and maybe a quick test too.· I expect to have ground buss issues (as the cars gnd is a couple volts higher than the stamps)....but the datasheet is pretty good for telling how to get around that....might just use opto's to isolate (that's the easiest me thinks!).

    http://www.elmelectronics.com/DSheets/ELM322DS.pdf
    here's a quick link to the datasheet (hope that works!).
    Anyhow, they weren't too expensive...but KNOW what protocol you're car uses!· The Manufacturer's service manual will tell you....I have a chrysler product which stated a different protocol for what my '02JeepTJ actually uses....so some manufacturers' switch between models...beware!


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    ·

    Steve
    http://members.rogers.com/steve.brady
    http://www.geocities.com/paulsopenstage

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • steve_bsteve_b Posts: 1,563
    edited 2005-01-06 20:42
    Hey guys,

    I just finished hooking up my circuit and tested it to my laptop.·
    We're getting a whack of Canadian weather at the moment and I'm not eager to sit outside and try the other end of the comms.
    But just for now I've been able to talk to the IC.

    Here's the circuit I used and a quick image of what to expect at the prompt.

    In the schematic I ran out of 3904's and used a 2N2222...also, there's a requirement for a 9.1V Zener.· I had to use 2 4.7Vzeners inseries.·
    And ended up using 1uF caps instead of the 0.1uF.· Success nonetheless.
    Upon power up of the circuit, the ELM322 IC responds to a successful startup with it's name and version followed by the ">" as it's prompt (image included).

    My thought is to interface with this IC and do the simple stuff with the stamp.·
    It's really all that challenging so far as interfacing the stamp to a nicely prepped rs232 line, so eventually I'll try to reverse engineer the ELM in order to replace it with the stamp.· Babysteps!!

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    ·

    Steve
    http://members.rogers.com/steve.brady
    http://www.geocities.com/paulsopenstage

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
    pdf
    pdf
    elmvpw20.pdf
    290K
    ELM comm OK.JPG
    600 x 600 - 37K
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-01-07 16:22
    Steve,

    ·· I know *I* will be eagerly awaiting the results of your findings...Years ago we tried to develop an interface for the Z80 ACM we built...As you have no doubt found out, specs are hard to find without spending $$, and without a guarantee on a return, we gave up.· Now I'd be happy to connect my BS2 and read the codes without having to count pulses...Counting pulses is how I did it years ago...



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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
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