Thread: Confused Newbie

I'll piggyback off of this thread since I feel I've got many of the same questions as the OP.

I'm NOT looking to reprogram my car or spend 10 hours a week pouring over data, I want something that I can reliably plug into my 2000 Cougar or my 2000 Durango and figure out what my car has to say.

I've read that many devices don't read manufacturer's proprietary codes, is that a concern with Elm327 devices? I'd think it's simply the device's job to spit out the data and the software's job to do something intelligent with it. Can I get some clarification on this?

The software has all the brains. An interface into your vehicle is simply that. If the software was designed correctly, you can access manufacturer specific PID's through the ELM327... it is just all on the software. The same software can work with multiple interfaces simply by modifying the code in communication, but the basic concepts are the same accross the board.

Sorry for bringing up an old thread...

Yes the elm327 can read proprietary codes.

FYI Joey's hardware has risen from 200 to 300 bucks without software, not that it matters.

For anybody that thinks that pass-through is a great idea, I would suggest that you read some OBD2 standards. If the software lags at all your car will stop running properly. The injectors will not get the signal to open and close at the correct time, and the plugs won't get the signal to fire at the correct times, etc. It is also a bad idea to be actually driving your car around with this mode set, unless you have dedicated hardware and software that can deal with it. IE NOT a carPC. Oh and I should mention that if you are driving around with pass-through on and your car pukes, you have successfully VOIDED your warranty.

So the reason that it is fast is because it has priority. Where as an elm type of interface is completely safe to run in your car 100% of the time.

In another thread he mentions that his is 100X faster. BS. So that means that when an elm can pump out a message at 30x/sec his can do it at 3000x/sec. Sorry dude, it doesn't get sent that often. He's talking about bus bandwidth, bla bla bla. Who cares, it is totally wrong for a carPC application. I'm not doubting that his hardware is great, and has excellent specs and potential, just not in a car PC, nor for a DIY'er.

Your car, your choice.

There is an even cheaper OBD2 multiprotocol scantool check out www.obdpros.com, it maintains compatibility with all ELM327 based OBD software and atleast 15% less than any other tool out there in the market.

The kicker is it will let you also change baud rates without opening the box which none of the other ELM327 tools allow plus it has support for speeds between the PC and the scantool upto 128000 BPS.

Of course I have a biased opinion but check it out for yourself there is a no risk 30 day return policy so you have nothing to loose.

Paul
www.obdpros.com

Reading manufacturer specific data has little to do with the tool, it's in the software. ELM 327 can be used to read manufacturer specific data, as can almost every other OBDII interface.

Originally Posted by air1kdf

For anybody that thinks that pass-through is a great idea, I would suggest that you read some OBD2 standards. If the software lags at all your car will stop running properly. The injectors will not get the signal to open and close at the correct time, and the plugs won't get the signal to fire at the correct times, etc. It is also a bad idea to be actually driving your car around with this mode set, unless you have dedicated hardware and software that can deal with it. IE NOT a carPC. Oh and I should mention that if you are driving around with pass-through on and your car pukes, you have successfully VOIDED your warranty.

FYI it's not "my" cable, I just work for DrewTech along with a lot of other engineers. Naturally I work on CarPC projects on the side as a hobby.

I'm not sure what you're talking about. A PassThru (J2534) cable uses a standard device driver just like modern printers, mice, keyboards, or sound cards. You're still using the same basic network protocols and you're right that the ELM327 can do most of the same things but slowly. As an analogy -- my cellphone and my Core 2 Duo can both get on the internet; it doesn't mean that the experience is the same. And it doesn't mean that my Core 2 Duo is dangerous just because it's fast.

Let's clarify -- with enhanced datalogging you tell the PCM "please send me X,Y,Z parameters continuously". The module will start streaming parameters at a rate determined by its real-time OS. It's a standard service provided by the ECU and factory/high-end scantools (Tech2, WDS, etc.) use the same technique. If the PC or PassThru interface can't keep up, you might miss data but that can't affect normal operation of the ECU. You can tell the ECU to spew information in its free time but it won't cry if you don't actually listen.

Originally Posted by air1kdf

In another thread he mentions that his is 100X faster. BS. So that means that when an elm can pump out a message at 30x/sec his can do it at 3000x/sec. Sorry dude, it doesn't get sent that often.

I've made quite a few posts over time. Please let me clarify:

The products I work on (CarDAQ, Mongoose, etc.) have lots of memory and lots of processing power. They can handle a fully-saturated bus which is useful if you're trying to reverse engineer or "sniff" the network. This is where the 100x estimate comes in. Speed is invaluable if you're hacking on the ECU reflash algorithm and you can't afford to drop a single packet.

But you're right, relatively few people are engineers and care about bus bandwidth. That's why I design the JVCI library that programmers can use to support enhanced datalogging. In this case, speed still matters. Ford and GM high-speed datalogging modes will continuously send a data packet (bundle of 4 or 5 parameters) every 5ms to 10ms. If you use these modes so the ECU sends data 10x faster, you'd want a cable that can keep up.

Originally Posted by air1kdf

So the reason that it is fast is because it has priority. Where as an elm type of interface is completely safe to run in your car 100% of the time.

Of course scantool software and cars could always have bugs. The recent Ford diesel trucks are famous for the number of software updates. On an early 6.0l diesel I violated P2_CAN MAX (sae j1979 page 12) and had the engine controller reboot on me while driving down the road. It was shocking but my software was working outside of the specifications so I had it coming to me. I also saw an early vehicle (97?) that would reboot when you asked for a specific parameter. Bugs are just a fact of life. That's why all DrewTech products have field upgradeable firmware and we post monthly updates to work-around problems with specific vehicles.

There's nothing wrong with correctly using a service provided by the ECU. If it voided the warranty to use a scantool, all the non-dealer repair shops would find it quite difficult to repair cars.

I can confirm that the ELM327 interface is slow, especially when you are using the interface for its CAN capabilities. What would really help people are some hard numbers to comparing interfaces. We plan on releasing some hard numbers that show some of the query rates of the various hardware tools out there. From what I have seen, I think you will find ELM is one of the last, if not THE last on the list.

I have yet to get into the OBD game, but it sounds like to me if you just want it to read info and do basic things, get the ELM device, but if you are hardcore and want to do more with it get the cable. Is that assumption correct?

Originally Posted by fatejd

I have yet to get into the OBD game, but it sounds like to me if you just want it to read info and do basic things, get the ELM device, but if you are hardcore and want to do more with it get the cable. Is that assumption correct?

That's pretty much it, Example: even in the case of PWM protocol where data is being sent at ~40KBPS the OBDPro is able to keep up with the messages at higher baud rates.

Now for CAN you cannot keep up with the speeds since the data comes in at 500K but you have the option to filter data and at that point there is really no need to want to keep up with all the messages unless you are doing some high powered reflashing etc.

It's the general 80/20 rule sure the OBDPro keeps up with the data 80% of the time and in the 20% cases where it cannot you can resort to filtering to get at the right data, now why would you spend 80% more money for something that you will never need? I am talking about the average hobbyist, not the high powered folks that joey was referencing above.

Having said all that; joey definitely has a point re speed but then again the cray supercomputers are orders of magnitude faster than your average pc but how many folks own a cray? But again if I could afford a CARDAQ I would definitely buy one because the speed factor would certainly appeal to my "Tim Allen " more power/speed mentality


Paul
www.obdpros.com