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Car Forum / Pontiac / Pontiac Cars / May 2009Confusion about CANbus vs. OBD-II?
Sorry about the crosspost, but I own a Pontiac and a Subaru, and this topic is relevant to both anyways. So I recently got myself an OBD-II car code scanner cable for my laptop, and during research I found out that all cars after 2008 will have to be CANbus compliant. They made a big deal out of specifying what cars prior to 2008 are already CANbus-capable. I didn't want to have an obsolete tool for any future cars I might buy, so I looked up what the differences were between CANbus and OBD-II. After reading up various websites about CANbus, such as this one: http://en.wikipedia.org/wiki/Canbus So I found out that CAN stands for Controller Area Network, and that it seems to be a networking specification for car components, similar to the network specification that connects your PC to the LAN. It doesn't seem to be specifically about diagnosis of faults in your car, just general internal communications between components. So I'm thinking do I really care if my fuel injectors communicate with my power window motors? Basically, all I wanted to know was how does it affect me? Do I need a new cable to connect to the car, or do I keep using the existing OBD-II cable? My feeling is that nothing has changed, and that they just added a few more codes to the standard OBD-II codes (the P0xxx codes) and the proprietary manufacturer codes (the P1xxx codes). I think all they did was add some additional diagnostics codes to check whether network connections are working between the components on a CANbus, but the format remains the same. The additional codes are the Uxxxx codes, as listed in this link: http://www.aa1car.com/trouble-codes/can_codes.htm I think this might be what the case is, just some additional codes. But the method of connection is exactly the same as before, and that we're not really going to be plugging our scan tools directly into the CANbus. Yousuf Khan Hi Yousuf! >Sorry about the crosspost, but I own a Pontiac and a Subaru, and this >topic is relevant to both anyways. My understanding is that the CANBus allows you to do things like use a laptop and Bluetooth adaptor to communicate with the ECU (as opposed to the hard-wired ODBII cable), allows the tire pressure monitors to communicate with the car instrumentation, etc. I'm at least reasonably certain that the presence or absence of the CANBus hardware will not affect the functionality of the "standard" ODBII interface. But I've been wrong before, alas ;-) You might wander over to one of the MegaSquirt forums (MegaSquirt is a DIY stand-alone engine control system. http://www.msefi.com/index.php) and ask the ECU gurus over there; I seem to remember some discussion regarding incorporating CANBus into the MS platform. Good chance you will learn way more than you ever wanted to know about the subject. There are probably some OBDII forums out there as well, but I'm not familiar with any. If you get satisfactory answers, do let us know what you find out. ByeBye! S. Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101 > My understanding is that the CANBus allows you to do things like use a > laptop and Bluetooth adaptor to communicate with the ECU (as opposed > to the hard-wired ODBII cable), allows the tire pressure monitors to > communicate with the car instrumentation, etc. Using a Bluetooth connection as your wireless OBD cable instead of a real OBD cable seems a bit far-fetched. I'm sure that such a module can be built and connected through CANbus, but I don't think that's an existing functionality of CANbus. One of the examples of Bluetooth-CANbus usage in automobiles that I've heard of is a bit more mundane. In that example they talk about using a Bluetooth adapter to connect a handsfree microphone to the car's speaker system. When a call comes in the handsfree automatically mutes the car stereo through CANbus. Another CANbus usage might be to tie the car stereo volume control into the engine rpm and road speed sensors, to auto-adjust for road noise. Another usage might to tie a taxi meter into the road speed sensor. > You might wander over to one of the MegaSquirt forums (MegaSquirt is a > DIY stand-alone engine control system. http://www.msefi.com/index.php) > and ask the ECU gurus over there; I seem to remember some discussion > regarding incorporating CANBus into the MS platform. Good chance you > will learn way more than you ever wanted to know about the subject. Okay, I'll try there. Yousuf Khan > You might wander over to one of the MegaSquirt forums (MegaSquirt is a > DIY stand-alone engine control system. http://www.msefi.com/index.php) [quoted text clipped - 6 lines] > > If you get satisfactory answers, do let us know what you find out. It would seem that that's not the right forum for asking these sorts of questions, since it is a pretty product-specific forum. Yousuf Khan > Sorry about the crosspost, but I own a Pontiac and a Subaru, and this > topic is relevant to both anyways. [quoted text clipped - 33 lines] > > Yousuf Khan Hi, Cable? What interface box you got? ELM327? Or sosmething else? All you need is Canbus compatible interface. > Hi, > Cable? What interface box you got? ELM327? Or sosmething else? > All you need is Canbus compatible interface. Yeah, it's a USB to OBD-II connector that fits on a PC or laptop. I think they call it ELM327 or something like that. Yousuf Khan >> Hi, >> Cable? What interface box you got? ELM327? Or sosmething else? [quoted text clipped - 4 lines] > > Yousuf Khan Hi, 327 is compatible with Canbus. I use it with my notebook. Works well. Fixed a few CEL prblems such as knock sensor, O2 sensor, misfiring cylinder, etc., etc. Tony, I have a question. I have been looking into an OBD-II interface; but it is a case of the more I read the more confused I get. Which unit do you have? Comments and suggestions welcome. >>> Hi, >>> Cable? What interface box you got? ELM327? Or sosmething else? [quoted text clipped - 9 lines] > Fixed a few CEL prblems such as knock sensor, O2 sensor, misfiring > cylinder, etc., etc. > Tony, > [quoted text clipped - 16 lines] >> Fixed a few CEL prblems such as knock sensor, O2 sensor, misfiring >> cylinder, etc., etc. Hi, ELM327 and I use USB connector. I had ELM325 with serial connector but I replaced it. Hi, Which software do you use? I think most of the units I see are using the same hardware; but with their own software. Any specific recomendations there? I have found 3 variations. ODBPros, ODBCOM and ProScan. Prices are pretty even; but the software is were the variation comes in. Most allow software updates for life. Feedback appreciated. >> Tony, >> [quoted text clipped - 20 lines] > ELM327 and I use USB connector. I had ELM325 with serial connector but I > replaced it. > Hi, > 327 is compatible with Canbus. > I use it with my notebook. Works well. > Fixed a few CEL prblems such as knock sensor, O2 sensor, misfiring > cylinder, etc., etc. So is the ELM327 the little chip that's inside the OBD-II cable? Yousuf Khan >> Hi, >> 327 is compatible with Canbus. [quoted text clipped - 5 lines] > > Yousuf Khan Hi, It's small interface box with connectors at both end. One end goes to OBDII connector, one end goes to USB port on computer. You need two piece of cables. That's what I got. >> So is the ELM327 the little chip that's inside the OBD-II cable? >> [quoted text clipped - 3 lines] > OBDII connector, one end goes to USB port on computer. You need two > piece of cables. That's what I got. Yeah, that's what I meant, the little box at one end of the cable where it goes into car plug. Yousuf Khan |
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