It had been mentioned in another thread about 95-97 MY changes that one potential area of evolution was OBDII compatibility/functionality.

Does anyone have any experience with code readers, etc that would indicate any issues with the earlier model years, or similary any significant improvements with OBDII compatibility from 95-97?

For example, for the last generation Buick Riviera which ran from 1995 through 1999, 1995 was an ODB 1.5 year. This was the only year where the ECU was OBDI but the connector/interface was OBDII and thus most readers are not compatible. And in 1999 the ECU changed enough to introduce some limitations to tuning capabilities as well.

I am curious if any such caveats exist for the 1995-1997 model years with regard to OBDII support.

Thanks
Al

 

No they were all OBD-II compliant (allegedly). I think the integration was much better for 96 & 97 cars, it is a bit flaky on the 95s to be honest. Some of the readings make no sense and the ECM very rarely sets a CEL.

I use both an Innova 3130 and an app for my iPad/iphone called Fusion and they both appear to work fine but I'm not sure I always trust what the ECM is telling them

 

The best you can hope for is to read live data and try to sort things out yourself. This is based on my own experience with my 95xjr with the innova 3130.

 

In my experience AND according to numerous reports on this very forum, I believe it is grossly inaccurate to say that the X-300s "ECM very rarely sets a CEL". Misfire detection stinks, yes, but they set all sorts of codes, just have a look at the archives. And, for the most part, the codes are accurate and can quickly lead to a valid diagnosis.

AllanG, I would say you have been extremely lucky if your X-300 seldom sets codes!

 

Thanks for the feedback!

Al

 

Ross,

My car has no problem whatsoever in setting codes and set codes on a whim, often for no reason at all but it rarely sets a CEL. I'm not sure I would call myself lucky, I would rather get a heads up if there was something wrong

 

Allan,

You know you can replace that burned-out CEL bulb in the instrument cluster, don't you?

(sorry, couldn't resist!)

Cheers,

Don

 

Well, I don't know how you can on one hand say your car sets codes on a whim for no reason, and then say you would like to know if something is wrong. If it sets a code, SOMETHING IS WRONG! It may be the thing setting the code, the ECU, but something is wrong. My 200,000 plus miles in a MY 95 X-300 produced numerous codes and CELs and I assume they all meant something.

I am being adamant about this because many folks are lead astray by thinking the code is in and of itself the problem. It is an indication of a problem, that requires analysis to figure out.

Let me be specific:
1) I got several EGR flow errors fixed by cleaning the EGR.
2) I got many lean burn errors fixed by finding and correcting whatever air pipe was leaking.
3) I got ABS faults, fixed by soldering the loose motor connection.
4) I got secondary air flow pump faults due to a bad secondary air pump
5) I got evap faults due to a bad gas cap, at least the new cap fixed it !
6) The loose MAF plug set a MAF flow code.
7) I got CAT efficiency faults corrected by replacement of the bad oxygen sensors.


Now, my high idle problem was NOT accompanied by a code, so I had to diagnose the TPS calibration by trial and error. Not every mifire was accompanied by a code, but some were. I had to find the bad spark plug on my own. Several CAT efficiency codes cleared themselves without intervention, but who can say the catalysts might not be innefficient after 275,000 miles.

Perhaps you would like to post your anomolous codes and we can help you analyze them!

 

Al,

I can't speak to real-world OBDII functionality, but I happened to find a brief history of the development of the GEMS Engine Management System in an online book about tuning Rover V8s (GEMS was developed by Lucas for Jaguar and Rover jointly). According to this history, all vehicles sold in California had to "comply generally" with OBDII by 1994 and "totally" by 1996. When first tested by the California Air Resources Board, the 94/95 system only failed on "engine backfire," which didn't prevent the system from receiving approval for sale in California because the issue was deemed minor and the rest of the system "complied perfectly."

If you're interested in such things, here's the link to this book, which is available for reading online:

How to Power Tune Rover V-8 Engines: For Road and Track - Des Hammill - Google Books

Cheers,

Don

 

Thanks Don, that is indeed VERY interesting!

 

I use TorquePro for Android but with a $15 ELM 327 Bluetooth adapter instead of the $100+ ones recommended by the App developer. For the most part, I use it to clear the secondary air code (P0411?) when it surfaces....sporadic, but average about 1/mo. Ross is right, that code is indicative of a problem with the secondary air pump - the thing is, I simply don't care whether the car blows air into the exhaust stream to warm the cats up quicker for emissions' sake. or not.
I've logged data with it and I get several blank fields, but some of those are just unsupported, others I know work because they populated when the adapter was new, but not after a bit of use. My car is MY95, but it would be impossible to say which parameters are missing due to incomplete implementation of OBDII and which are missing because I'm a cheap SOB on my 2nd or 3rd Chinese ELM knockoff rather than on the more expensive one recommended by the software author? I can say, for my purposes, the OBDII implementation is sufficiently accomplished that the $5 app + a couple of BT Adapters nominally $15 ea. or so have been funds well and wisely invested.


I read somewhere here in this forum that AutoEnginuity with Jag Module may not read chassis codes on the 95's whereas for 96-97 it will.

 

Ross, what I meant by this is that my ECM will set codes but almost never illuminate the CEL (yes the CEL works). I would like to know if the ECM thinks they may be a problem and decide for myself if it is real or not.

Yep, most of the time that is indeed true. Ross, I know you understand this but for the benefit of others who may not, the ECM receives data from many sensors/devices/inputs etc. However, it is the OBD-II programming that decides whether or not to set a code and also whether or not to light the CEL. The programming looks at the data and uses a number of routines to decide if the data presents a problem or is an anomaly.

So for example, if a tiny impurity in the fuel caused a cylinder to misfire once, the software should determine that it was an anomaly and not set a code. However, if the fuel supply was contaminated and caused repeated misfires, at some point the software should set a code, initially probably a P0300. If after a pre-determined number of operating cycles the misfire continued the software should then set a CEL. This programming was immature in the early 95MY cars a fact acknowledged by Jaguar who issued a TSB on at least one occasion stating that codes were improperly set due to "excessively tight tolerances in the programming" (system was too sensitive) and issued a newly programmed PROM.

Agreed, however, as in the example above if the software sets a code for an anomaly, no amount of troubleshooting will find the answer, leading to much frustration!!!!!

I ABSOLUTELY agree with you that every code should be investigated but the fact that you will find literally hundreds of posts that say 'I just reset the code and it never came back again' might suggest that the programming was not optimal?

And who's to say that it wasn't a false flag Cats can become inefficient I suppose but would they just become efficient again on their own or could it be an anomaly?

As always, I appreciate the wonderful helpfulness of this forum and believe me if I find a code that I cannot resolve I will be the first to post here

In addition to the occasionally anomalous code, there are other issues with the OBD-II implementation such as the wacky LTFT readings, mis-calibrated mass air values etc.

 

Yep, I agree. I suspect you are monitoring (and maybe resetting?) codes that are "pending" status, or your codes are recorded without a CEL since they previously came and went ("stored" codes). Even these can help lead to a diagnosis of another specific code, even though the problem was not serious enough to latch the CEL.

Obviously, you and I have had different experiences with the X-300 ecu fault functions. My automotive experience dates to the days when listening, smelling, and looking were the primary diagnostic tools. I consider the electronic controls on a car to be a hobby and I am really impressed with the level of control now used on IC engines. And yes, the X-300 was an early OBDII implementation, but many problems can be accurately and quickly resolved by careful observation of codes, and charts of LTFT, STFT, airflow, engine load, and TPS. I seldom need to take out my oscilloscope for an OBDII car, unless itis just to learn what the ECU is doing in the background.

Again ,while your points are valid to some extent, the tendency for the passerby posters on here is to say something like "my car is sluggish, what's wrong?" without any comment about the CEL, the codes or anything else. That leads to a bunch of conjecture and anecdotal replies (all offered in good faith!) of the myriad parts that need to be replaced, instead of the correct question of "What do the diagnostics say?" In my opinion, that happens because folks don't understand and appreciate the level of self checks going on in the car's control system.

I myself have two classes of cars I drive. I leave my new Jag alone and drive the hell out of it. I take my older Jags and try pulling plugs, introducing leaks and other such aberrant behavior just to learn what is going on in the controllers!

 

Ross,

I think we are essentially saying the same thing My response was to the OP's question about the OBD-II implementation in early X-300's. I do believe that the implementation was not optimal but I'm very glad to have it as more data is better than no data at all

I STILL believe that the first thing one should do in troubleshooting is to use one's senses. Look, listen, touch, smell. Then gather all information you can via OBD-II scanners, DVM, scopes etc. Then test circuits/systems to hone in on the problem. Find the problem, fix it and then re-test. I ALWAYS follow these steps as opposed to buying/swapping parts based on what I think as opposed to what I know

Unfortunately many owners and also mechanics!! try replacing parts first which apart from often not solving the problem and being an expensive approach, may also introduce another problem to the mix!

That is why I believe this board is such a useful resource for owners and mechanics alike. But you only get out what you put in. So if a poster says "Help! my car won't idle smoothly", he will get a myriad of responses such as 'replace your 'X' (EGR, ISCV, ECM, TPS, CKPS, CPS etc etc) along with dozens of other potentially valid suggestions. If he were to follow those suggestions (and many do) he could spend a lot of time and money and still not solve the issue, leading to a lot of frustration (many are )

 

Had plenty of successful use of the OBDII functionality on my '95, but I'm another who's never seen a CEL - would be nice to get a 'heads up', but I just keep an eye on it / check regularly.

The only oddness I've come across is the apparent inability to read LTFTs - STFT works fine though.

 

Here's a link to additional information on the early GEMS system as it was implemented in the Land Rover Discovery in a wasted spark setup (pairs of coils fire on both the compression and exhaust strokes).

Most of the document is just a basic introduction to the system, but the last two pages provide a list of changes that were made to the tuning as various behaviors were revised. I think it would be safe to assume that Jaguar had to make similar kinds of tweaks to the ECM tuning during the course of the X300 model life:

http://p38arover.com/rover/p38a/Engi...MS_Systems.pdf


Don

 

Hey guys, my problem is that my cel light goes on as it should when I turn the ignition on but I cant get my ecu to get to a readiness state or even set a cell when I unplug my MAF. Any ideas?

 

Hitch:
I would suggest starting a new thread rather than posting to this old thread. That may get your question more attention from the experts here.