This is the ECU that was in my '96 XJS 4.0 conv. when purchased. It doesn't seem to be the original as it's dated 04/01/00 (April Fools?).

Is there any documentation explaining the Part No., Ref. No., Type Code, the No. over the UPC and the No. 112158 under the Made in UK line?

How does one determine the correct ECU for a given vehicle? I know you can swap in different ECU's (I'm currently running on one from a '95 XJ6) but there should be a way to find out exactly what should be in the car.

 

No reply's?
I thought this would be of interest.

 

Hello;

As far as the date on your ECU I imagine its because it had to be replaced. It is not uncommon for the facelift cars to suffer from water ingress in that area. I lost two ECU's that way.

Because of my experience with ECU failure, I have two backup ECU's LHE1410 with different letters after them. They both worked well on the car when I tried them. AFAIK, any LHE 1410 xx will work, and if it does not, it can be programmed with the Jaguar computer

As far as you running a XJ6 ECU, I do not comprehend how that is possible, my understanding is that the car will run poorly. We tried one in my car a while back and it ran very poorly

 

Thanks for the response.
The ECU currently in the car is P/N LNA1410AE.
The story is . . . It wouldn't pass inspection with the LHE1410DH. The inspection computer could not read read some of the sensors. I tried resetting the ECU. Drove it about 60 miles. Went back and got the same result. I put int the LNA1410AE from a '95 XJ6 and the insp. computer read everything but 1 O2 sensor. Enough to pass. Prior to the swap I had high idle problems. With the LNA1410AE is runs smooth.

I'd still like to know why all the different numbers. I assume it's different versions of the software but there should be some way to find out what the differences are.

 

Lots going on here Pete. You will never get that car to pass inspection with that ECU. Most notably because the OBDII standard became mandatory with the 1996 model year. The 1995 ECU, while "technically" OBDII, is not fully implemented, so for inspection purposes it won't pass muster. Never will. I do know you can make an XJS run with a module from an XJ6, but it will never be long without a Check Engine light.
I'll see if I can't get in some of my information and straighten out the part numbers, but it will take a bit.

The date thing indicates the XJS had an ECU replaced at about 4-5 years old, then had a recall performed resulting in the R493 sticker with yet another part number.

Gotta run. I'll dig up what I can.

Cheers,

 

Steve,

Without wishing to derail pete's thread, could you explain what you mean about the 1995 cars not being fully OBDII? In the UK, there are no fundamental engine differences in 4 litre cars from the time of introduction of the AJ16 engine in April 1994. I have always understood that all 4 litre cars from that point are OBDII-compliant. I have an early AJ16 car and colleagues of mine have later AJ16 cars. They all seem to scan the same using OBDII readers. Is there some subtlety of difference in the ECUs of later cars? If so, do you know what are the differences and at what VIN point they came in?

Tks

Paul

 

Hi,

My 95 has been passing state inspection with a 96 ECU. The only difference that I know of between 95 and 96 XJS's is the wooden steering wheel and the brake system.

 

Actually it did pass.
It failed with the LHE1410 and passed with the LNA1410.

I did get a check engine light but it was just about a fuel level sensor. I reset it with my el cheapo ELM and Dash Command. No problem.

 

Well, it's not as easily cut and dried as you might expect. This will probably just muddy the waters, but here goes.

I haven't had time to find all the documentation in print, but I'll do the best I can with my recollection. OBDII was a standard that was mandated in the US, for cars of the 1996 model year and later. The 1995 cars got he AJ16 engine which was to have the new engine management that was compliant with the standard. Certain parts of the fully compliant system were omitted from some 1995 cars for who knows what reason; cost, I'm sure was part of it. For instance 1996 cars had some evaporative emission hardware that the 1995's didn't. A fuel tank pressure sensor and electric canister close valve as a couple examples. Some had twin carbon canisters, some had only one.
Obviously trying to use an ECM from a car that had that hardware in a car that didn't have it, would cause immediate Check Engine lights. It would be the same as disconnecting it on the original car. How swapping an ECM in the other direction would work is anyone's guess. Maybe it would work, maybe it wouldn't.

When I said 1995 the OBDII wasn't "fully implemented", I was referring to certain parameters or PID's that didn't report logically, and to the fact some fault codes and component monitors were missing. Examples are, 1995 didn't monitor catalysts as I recall, nor was misfire detection active. Well, it was there, but it would not set a Check Engine light.

Also for 1995, the STFT and LTFT values were jibberish. Attached are some scantool screens from my 1995 XJR and a like 1996 belonging to a friend of mine. One screen from my car is taken at a time when the fueling adaptions had strayed too far and caused running issues and high MPG. [I have to reset those adaptions about once a year, I know it's time when the fuel mileage goes way down] You'll see my LTFT reads +45%. But right after I have cleared the adaptions you can see it reads -100%. Not logical at all. I have found all 1995 AJ16's read this way.
My friend's '96 shows the trims report just like we would expect; zero as neutral and going positive or negative as necessary.

Another difference is the 1995 catalysts in the States were different than the ROW. [Rest of World] In 1996 we here got the same catalysts as everywhere else.

@paul -- this probably is why your experience differs from mine here. I neglected to consider the US/ROW thing when I made that post. [and I should have] Some of the following part number stuff may not apply to the UK, but then again it might.

Also attached is some part number info for the various models, years and wheelbases. Software is different even for SWB and LWB versions of each model year sedan. This is why some inspections will fail a car with mix & match replacement ECM's. I have found some inspections/inspectors are more in-depth than others. Some will catch the mis-match and some will not. It's a roll of the dice in those areas.

Hope that helps some. I know it's confusing at times.

 

Steve,

That's really useful info. Tks for that. As you probably realise, we're fortunate not to have all that emission stuff, pressure sensors, carbon canisters, air pumps etc etc. I'm so glad that we just have our XJSs the way that Jaguar intended! Hence my view that an early UK 94 AJ16 XJS isn't any different in the engine compared to a 96 (apart from minor camshaft timing which drops a bit of power anyway).

However, I am interested in your view that the STFT & LTFT figures may be gibberish on a 94 AJ16. If I get the chance, I'll monitor mine this weekend on my Torque Pro smartphone App and see what figures I get. Your charts are a great help.

Tks again

Paul

 

Very interesting. Indeed the STFT and the LTFT parameters have always been completely out of bounds in my early production 95 car. I always assumed it was because of the cracks in my intake manifolds .

Well, I can tell you that the ECu from a 96 works perfectly well in my car with no lights at all.

 

Steve - Great info. Thanks for taking the time to post!

So . . . the ECU that was in the car originally was the correct LHE1410DJ.
Now the question is; why does it run so much better with the LNA1410 and how do I go about fixing it so it runs with the LHE?

With the LHE I had a high idle and the inspection computer showed "incomplete" on 3 sensors. With the LNA idle is smooth and steady at 600 RPM and only 1 sensor showed the "incomplete" (I think it was the O2).

 

So here is the logging of my XJR today, while it is running perfectly. The last reset of fueling adaptions was several months ago. In fact I'm sort in trouble with that right now as our PDU drive is on the fritz. So at the moment I don't have a device that can reset the adaptions.

Couple other things to mention, the AJ16 NEVER reports the MAF value correctly. You see it reads something like .06 g/sec. That's obviously false. I once thought that was just a decimal incorrectly placed. But in testing at various idle and high load flow rates, it doesn't seem to be the decimal point alone.

Also, While the STFT and LTFT were mandated PID's, Jaguar didn't really use them. They used PID's of their own for fueling and diagnosis. They called them Air Mass Flow Rate [AMFR] and Fuel Mass Flow Rate [FMFR]. On top of that, I have never seen an AJ16 set a normal lean or rich DTC, meaning P0171, P0172, P0174 or P0175. Instead Jaguar used P1176, P1177, P1178 and P1179. These were pretty well explained in bulletins way back when, 5.1-31 for sedans and 18-53 for the XJS. One is attached; and you will note that each sedan model year has a different load range to maintain when confirming fueling PID's set correctly. There has to be some reason for that.

They also describe the adaption reset I always refer to, called 'Reset Adaptive Terms' in the PDU menu.

In your particular case, you can't judge whether your car is running CORRECTLY on either ECM unless you have some configs done with the diagnostic tool. One is the fueling adaptions, the other two are:

*Throttle Potentiometer Adaption, which can be the reason your idle is so different when you switch ECM's
*Oxygen Sensor Orientation, by which the ECM figures out which O2 sensor is plugged where, and what it's location is.

Without being able to perform these operations, people can be thrown all sorts of curves that seem to make no sense when trying to diagnose things.

As usual, there are lots of things going on in these systems that most people don't realize.

Cheers,

 

So it looks like my first step is to 'Reset Adaptive Terms' - Fueling Adaptions, Throttle Potentiometer Adaption and Oxygen Sensor Orientation.

Is that the correct terminology I should use when speaking to someone with a PDU?
Might that fix the problem or just get me to a place where I can properly diagnose it?

 

Correct on all counts.

PDU, WDS or IDS can all do the last two operations. Unfortunately PDU is the only device I have ever found that can do the 'Reset Adaptive Terms'.

Good luck!

 

Hello again - I spoke with a local indy and he claims that the Adaptations will reset/adjust themselves if the car is driven long enough. That seems to be incorrect. I believe he has the AutoEnginuityScanner. Would it be worth it to see what he can come up with using his scanner or would it just be a waste of time?

 

He obviously isn't familiar with the idiosyncrasies of the AJ16. Technically speaking, what he says should be true. But that "long enough" could be weeks in this case. This was one of the first runs at adaptive fueling, and they had not learned all their lessons. The adaption on this engine is painfully slow, and it doesn't have the limits that newer cars have. By that I mean, the adaptions can stray far enough on the AJ16 that it won't even run. I have repaired numerous cars, usually towed here from other facilities, that all I had to do was clear the adaptions and reset the throttle pot adaption to make the car run fine. Today's fuel trims have limits, usually plus or minus 25%. They can't go any farther than that. Not so with the AJ16.

These are rare and extreme cases, but they happen. Many people have never experienced such a thing, and therefore think I'm full of crap. Somewhere I have a couple short before and after videos of just such a car. One day I'll try to dig them up.

As far as the AutoEnginuity, I don't have any experience with it so I can't comment. They could have advanced and incorporated a program to do the adaptions. But as of right now, I know of no device but the PDU that can do it. Stupid as that is.

Good luck!

 

Steve - I'm starting to think that the best idea might be for me to take a road trip to Indianapolis !!! ;-))

 

Ordinarily, I wouldn't hesitate to say, "Come on up!", people have done that before! But at the moment I am without my PDU. Stupid drive failed and can't find a replacement, it's a Sony interface that went by the wayside 20 years ago.

Surely someone in your area must have a functioning PDU.

Good luck!

 

So I'm digging up an old thread.
Steve since it is hard to find a good ECU for an 1996 XJS, would one from a 1996 XJ6 work?
My ECU is not allowing the car to get to a ready state for emissions testing in PA