OBD II Question

[mopar 3 B]

OBD II Has been with us a long time now. It is just strange that on where can be found the desirable range it was built to run in. I have been on forms were it has been taken is a down right insult the question was even asked. I have found posting of upper and lower limits of function ranges with explanations of component function. Quit helpful if that is all one wants to know. I also have a factory 2003 electrical diagnostic Chrysler manual that eludes the issue but a great resource for checking components. But that information changes from brand to brand.
So not to drag this out any farther does any one know what the desired live data stream for OBD II in a freeze frame would look like? Is there such a thing?

 

[wagonman]

Not quite sure what you are asking? It seems you have a handle on OBD2 butfrom what I remember and it has been a few years Live data is one thing and freeze frame is another. That being said freeze frame can be triggered by a code or manually on some scanners. Global OBD2 is pretty much the same parameters for all car lines with some oddballs like German and Swedish cars. When the money lite comes on and triggers freeze frame look at data and see what is out of range I.E. fuel trim, MAF, Ect. It is helpful to try and recreate the fault within the same parameters when driving in live data mode. Some scanners are better than others and factory ones are best like a GM tech2 or the Mopar Darby, I found the Autell has some skewed software and the Snap-on Modis is about the best I have used. Thankfully I dont have to do this for a living any more. Hope this helps.

 

[mopar 3 B]

I understand all that but have no where been able to find acceptable perimeters. Some one had to establish them other wise there would not be errors. I have my own scammer and plug it in occasionally just to see whats going on. If the acceptables were known could replace things before that nasty light comes on in the dash.

 

[MoparLeo]

Instead of dancing around, what is your real question ? OBD 2 was just a government required second generation of the On Board Diagnostics system, more specifically to monitor Emissions related sensors/function. Each Manufactures' engines and computer systems are pretty much proprietary and purposely non-specific in some areas. That is why you have to go to the dealer sometimes because you must use the manufactures scanners and software that is not available to the public. Remember that the ecu for Mopars were locked for several years and could not be reprogrammed until they unlocked them.

 

[wagonman]

Instead of dancing around, what is your real question ? OBD 2 was just a government required second generation of the On Board Diagnostics system, more specifically to monitor Emissions related sensors/function. Each Manufactures' engines and computer systems are pretty much proprietary and purposely non-specific in some areas. That is why you have to go to the dealer sometimes because you must use the manufactures scanners and software that is not available to the public. Remember that the ecu for Mopars were locked for several years and could not be reprogrammed until they unlocked them.

I hear you Leo, yes the way each manufacturer test is proprietary but the values are set by the EPA and CARB. Just look at Evap systems and how many systems there are. Vaccum decay over a set time through an orifice the size of a Gnats butthole is one. Or pressure decay depending on the car line. As to monitoring it before it fails, dont fix it if it aint broke. Like a Mani-Cat on a Nissan, I think it is on its way out so lets replace a $1200 part. Like I said, glad I am done and it will only get worse. Carbs and a simple elect ign for me! Not to toot my own horn but I was a ASE master tech with a Advanced Engine Perf Cert and a Nevada Smog License to test and repair. I can imagine California is even worse with functional tests for HC CO and NOX, plus visual and tail pipe tests. Thanks Al Gore. Funny in Nevada testing is only in non attainment areas like Vegas and Reno, but not in Carson City where they make the laws.

 

[mopar 3 B]

So just whats the purpose of having live data if no one knows what a normal reading is? Almost 20 years into a system that was supposes to make testing uniform and we still have no base for the test? So thats the kind of crap we have to live with. Or do the manufactures have this info guarded that well?

 

[mopar 3 B]

So what

I hear you Leo, yes the way each manufacturer test is proprietary but the values are set by the EPA and CARB. Just look at Evap systems and how many systems there are. Vaccum decay over a set time through an orifice the size of a Gnats butthole is one. Or pressure decay depending on the car line. As to monitoring it before it fails, dont fix it if it aint broke. Like a Mani-Cat on a Nissan, I think it is on its way out so lets replace a $1200 part. Like I said, glad I am done and it will only get worse. Carbs and a simple elect ign for me! Not to toot my own horn but I was a ASE master tech with a Advanced Engine Perf Cert and a Nevada Smog License to test and repair. I can imagine California is even worse with functional tests for HC CO and NOX, plus visual and tail pipe tests. Thanks Al Gore. Funny in Nevada testing is only in non attainment areas like Vegas and Reno, but not in Carson City where they make the laws.[/QUOTE
So whats wrong with wanting to prevent the replacement of a $1200 part instead of waiting for that blasted engine light to come on? Cats normal dont go bad for no reason.

 

[wagonman]

Well lets look at normal fuel trim data, if it is high = adding fuel to adjust for a lean condition it is your job to find out why. A vaccum leak, clogged injector, dirty MAF Ect can cause a lean condition. IIRC a p0420 indicates a faulty cat conv. Is the converter bad or is it a bad post cat O2. The tests are out there as well as the values for the sensors. Service manual flow charts are one resource. A good lab scope is a tool to evaluate an O2 sensor as well as others. As far as writing the software for the OBD11 procedure you will need a degree in engineering. Cant help you there.

 

[mopar 3 B]

So that explains why many just throw parts at it till something works. What a silly way to do things.

 

[65wgn440]

Yes, that's what people who don't have the talent or equipment do. Not PROFESSIONAL Techs ! You seem to be asking for a list of acceptable working PARAMETERS of every component (sensor, switch, solenoid, etc) that is monitored by vehicle's PCM. You would probably need to contact a Government Agency (good luck) or become very good friends with a Big 3 software engineer to get that. If your curiosity is really that strong, you could start to compile your own list, as complete or lacking as it may be, by going through every manufacturers diagnostic routine, for every code that could possibly be generated, and gleaning your desired parameters from the info contained there in (IF provided). As mentioned earlier, a GOOD scan tool could/would be a valuable asset (figure spending $5k to $10k) for this endeavor. And honestly, to use this information as you desire, as preventative maintenance, you would most likely need a decent oscilloscope, also.

 

[wagonman]

Being retired I still have a curiosity in late model cars. Two of my YouTube channels I watch are Real Fixes Real Fast and South Main Auto. On one episode SMAC chased down an Evap code that led to a faulty P.S. pressure switch. Took 2 Scanners with 4 channel lab scopes to find it and LOTS of chasing. The guy has about $50 grand just in daig tools.

 

[mopar 3 B]

So the best one can do is freeze frame a live data stream on a system that passes emission testing and saving it for referencing for each vehicle. My scammer will at least do an emissions scan and let me know if it is ok or not.

You would think the people that look at this every day would know what realistic ranges are. But I guess not and to think we use to tune by ear and feel.

 

[wagonman]

Sure if you do it day in day out you get a feel for what is out of whack. Working at a dealer you see the same issues and can guess just by the description on the work order whats is up. A bad practice that will bite you in the ***. At an Independent shop shop with every thing under the sun coming in you have to verify everything. Can your scan data be down loaded to a PC and then store it for future reference? If you really want to get ambitious get a subscription to one of the online repair info services like Motor manuals or Alldata. $180 a month is out of my league but Pro shops are forced to.

 

[mopar 3 B]

Can download it or print it out so storing it is not a problem. Have not had a problem with diagnostics. Engines are still engines with added controllers. Learning what they do and what they work with has been the biggest battle. Create a path and the problem can be found eventually.
On the 99 Avenger I had to completely rebuild the front suspension to take care of a random engine misfire. Problems are not always were they should be and have gotten use to it.

 

[MoparLeo]

Still don't get exactly what mopar 3 B wants. A general number for everything or are you interested in a particular number for a particular application ? Get specific. a/f ratios have not changed, only how to adjust and read. Timing ? Constantly adjusted, computer. Obviously Modern computer controlled, monitored systems are under constant management. Just like the carb days, only difference now is the sensors/computers that now monitor and make adjustments many times per second to the same "ideal" standards. Just use a high energy ignition system and an O2 sensor monitored a/f meter.

 

[Ranger16]

I think the parameters you are looking for are probably in the FSM (I know they are for Cadillacs), but I don't think any of them are in print anymore. A subscription to Alldatadiy ($29.95/YR) would most likely have what you are looking for. https://www.alldatadiy.com/buy/index.html

 

[mopar 3 B]

Still don't get exactly what mopar 3 B wants. A general number for everything or are you interested in a particular number for a particular application ? Get specific. a/f ratios have not changed, only how to adjust and read. Timing ? Constantly adjusted, computer. Obviously Modern computer controlled, monitored systems are under constant management. Just like the carb days, only difference now is the sensors/computers that now monitor and make adjustments many times per second to the same "ideal" standards. Just use a high energy ignition system and an O2 sensor monitored a/f meter.

Just a general numbers for everything. I know the information keeps changing I have watched enough live data to understand that. Things like fuel pressure and water temperature are pretty stable items unless there is a problem some where.
Fuel trim and oxygen sensor numbers are the biggest mystery. With out understanding these what good would even installing bugs for O2 sensor do in our old rides.

 

[mopar 3 B]

I think the parameters you are looking for are probably in the FSM (I know they are for Cadillacs), but I don't think any of them are in print anymore. A subscription to Alldatadiy ($29.95/YR) would most likely have what you are looking for. https://www.alldatadiy.com/buy/index.html

Thanks I will look into it.