This is more follow up to my ongoing shifting issue that some of you may recall. I am going to try replacing the ECM as my last gasp. My user panel probably lists all the other threads I've started on this issue over the years if you're curious. Suffice it to say I've been down many, many paths, and have now reached the ECM.

Anyway....

The part number of my ECM is LNC1410AD/001 (VCATS). My car is a relatively early 1998 XJR. From Jaguar Classic Parts and Jaguar Heaven in California, I have learned that my part number was superseded by part number LNC1410CA. Jag Heaven has an ECM, part number LNC1410CA/001. This would be the same as my VCATS number (001).

My questions are:
1. Will the replacement ECM work? Is it required to have BOTH the precise exact same part number and VCATS number?
2. From the forum, I have learned that I will have to do an immobilization setup no matter what, but will that suffice in this case, or will I need complete reprogramming?
3. Is there a way to reprogram the entire ECM, lock stock and barrel, based on my car's VIN?
4. Who can do the reprogramming?
5. Does the ECM have to be installed for it to be reprogrammed?
6. I think the ECM has to be installed for the immobilization setup, is that correct?

I will have more questions about who can do these procedures and other logistics, if any of you can point me in the right direction first. Thank you!!

 

The ECM needs to be from a 1998 XJR.(possibly from a 1999 XJR?, they are BOTH AJ26) A normally aspirated ECM will not have the correct software version.
The ECM NEEDS to be installed in the car so it can communicate with the CAN bus during 'immo-setup'.

bob

 

Thanks Bob. So an updated part number will be ok, as long as it comes from a (preferably) 1998 XJR. Does it need to have the 001 VCATS number? If it has the 001 VCATS number, will the immobilization setup be sufficient to make it work?

Thanks again. I've read through several of your responses to this topic on other threads, which is where I'm getting some of my answers (and additional questions).

 

The part numbers are often 'superseded' so that is not always a deal breaker but the /001 is important.
Like I stated earlier, the 1999 XJR US models were also AJ26 so the ECM from one might also work.

 

Aquifer, I have searched your old posts pertaining to the shifting problems you’ve been having. I admire your determination and how much money, time and aggravation you’ve been thru. Since we’re talking about the ECM, take a look at this guy under/behind the glovebox. Just start your engine up and see if it’s running.

ECM/TCM fan.

In my opinion, if the fan isn’t working, fix and field test it first before replacing the ECM.

 

I appreciate you looking back at all those threads! As to the ECM cooling fan....been there. I had some hope that the fan was burned out, and the ECM and/or TCM was overheating. But nope. . It’s actually pretty easy to see the fan running inside the ECM/TCM housing. Just lift up the ECM a little and it’s right there.

That said, I’m pushing pause on the new ECM idea. I’ve circled back to the blown fuse for the high side engine cooling fan. I thought I’d fixed it by replacing the fuse, but I had not. So I’m revisiting what made that fuse blow. Turns out there are a number of pinpoint tests you can run for resistance and voltage at the ECM and fan relay module. I found another problem. The voltage at pin 8 on the fan module is way too high. The book says if it’s over 10 volts, replace the fan module. I also found massively incorrect resistance on two pin tests. This is indicating that the resistor(s) in the fan module are bad and are not providing the correct feedback to the ECM.

Based on on those findings today, I ordered a new fan module. I do not know if this will fix the shifting problem, but I’ll find out! Since the two wires going from the ECM to the fan relay do not have the correct resistance (not even close), I’m hoping that this fault is causing the ECM to choose the wrong shift pattern when the high speed fans are activated by the ECM.

If nothing else, because of all this, I am gaining a deep knowledge of how these cars work!

Thank you for your input. I am grateful for any and all ideas, as you can probably tell.

 

I found an independent shop that did the immobilization setup for the replacement ECM I found. They charged $150, which I thought was reasonable. The programming went fine, and the replacement ECM works. Unfortunately, it didn’t fix my shifting issue. Other than the crusher, I’m out of options. Aside from replacing the entire car, I’m not sure what else there is to replace.

Still no error codes, the shift pattern simply changes when the car gets hot. It will not upshift until about 2,500 rpm, then when slowing for a stoplight, you can feel it downshifting and the problem starts all over. But only when everything is good and hot.

Maybe I need to revisit the resistance tests I did on the transmission temp sensor wire. Perhaps at higher temps, the sensor goes into some kind of fault. The conductor plate was replaced, so I can’t see how this is possible. Unless they stamped a new date code on the conductor plate, but did not replace it because the resting temp resistance tests ok.

Can anyone think of something I haven’t tried? It’s definitely related to temperature, and I really thought I was onto something when I found the blown high speed fan fuse. It only acts up when the car is hot.

 

It could actually be a hydraulic problem in the transmission (in the valve body). What is the mileage of your transmission?

A hydraulic problem will not trigger any codes. Worn valves in the throttle body could cause shifting problems (usually due to reduced hydraulic pressure) when the transmission fluid heats-up. There are many valve body repair kits for the MB 722.6 (example: https://www.ebay.com/itm/Transgo-Shift-Kit-Mercedes-Chrysler-Jeep-Sprinter-722-6-NAG1-SK722-6-A/201386149849?hash=item2ee38cc7d9:gj0AAOSwMmBVn~v q&vxp=mtr). If you google "722.6 valve body repair kit" or "722.6 shift problem when hot" you will find a lot of information.

 

The transmission was rebuilt about a year ago. Besides the shifting issue, it had developed a loud clunk sound inside the transmission when downshifting. The clunking issue went away with the rebuild, and I was sure that the rebuild would fix the shifting issue, but it didn’t. The repair shop continued to try and diagnose the shifting issue, and even went so far as to swap the rebuilt transmission with a used unit they had on hand. That transmission exhibited the same shifting issue when it got hot. The diagnosis has continued ever since, mostly by me, since the shop was baffled.

I had no reason to think I was being sold a bill of goods by the shop, but to make myself feel better, and because I was running out of ideas, I dropped the valve body out of my rebuilt transmission. The valve body had a recent date etched on it, and the conductor plate had a date from 2017 that was stamped in relief in the plastic - the little arrows pointing to the month and year. I felt confident that these parts had been replaced as I was told.

It is possible that the shop did not swap in the old used transmission like they said, but I think they did. Going with that assumption, is SEEMED like we had eliminated the transmission itself as the culprit. He seemed genuinely puzzled, and was trying to solve the problem. He would call every couple weeks and we exchanged ideas. He didn’t charge me for any of the follow up diagnostic work, and I finally went and got the car to continue the diagnosis on my own.

You may or may not recall a prior post where I discussed various pinpoint tests, and how grossly wrong my readings were in relation to the manual. I never really reconciled why my readings were different than the manual, but the manual’s chart did not make any sense in several tests, so I chalked it up to an incorrect manual version, and sort of moved on.

There is nothing left to try, except, obviously, whatever is causing the issue. But I can’t imagine what that would be because I think I’ve swapped everything possible at this point. The transmission, the linear switch in the shifter, various relays, the ECM, the TCM. I have done continuity and resistance tests on all of the wires going to and from the transmission.

It is heat related, and that’s all I’m sure of at this point. Yet i have never received a transmission high-temp trouble code. Or any trouble code, for that matter. It just suddenly shifts funny when it gets hot. What do I mean by “it gets hot”? I’m not absolutely sure. The engine gets to operating temperature pretty quickly, but I assume the transmission warms up a bit more gradually. The shifting issue only occurs after a long drive, followed by start/stop driving.

The car is otherwise in immaculate condition. I’d crush it if not for that....

 

Well, you can perhaps take a (financial) risk and buy a rebuilt valve body - https://revmaxconverters.com/product...em-valve-body/.

They say it will fix "the many shifting complaints with a worn out valve body. The most common of which are: delayed engagements, harsh engagements, flair shifts, delayed shifts, harsh upshifts, harsh downshifts, slippage in gear while driving..." etc

 

I suppose the transmission fluid gets thinner as it gets hotter, which may explain why a worn or cracked valve body would exhibit these symptoms only after it heats up significantly.

If the valve body is the issue, I would have to believe that the shop did not replace the valve body, but just etched a new date on my old one. I would also have to believe that the shop did not swap a used transmission with my rebuilt one, in an effort to eliminate the transmission as the culprit during the subsequent diagnostic process. The chances of two transmissions exhibiting the same symptoms are exceedingly remote, so it’s more likely that he did not actually swap it.

I’m not saying it’s not possible, I’m just thinking out loud. I really appreciate the suggestion, because the worst case scenario may indeed be true. I’m thinking very hard about taking a risk and getting another valve body like you suggested.

I would like to get a new conductor plate too. All I see are cheap knockoffs on eBay. Do you know if “real” ones are available? If I decide to go this route, I’ll want to replace the conductor plate while I have the valve body out.

Again, many thanks for the suggestions. I’m obviously unsettled on what to do.

 

Here's a couple (you can also search for "genuine mercedes 722.6 conductor plate").

https://www.ebay.com/itm/Genuine-Mer...gAAOxymspSDMwG

https://www.ebay.com/itm/Mercedes-Tr...wAAOSwuytcNNHU

 

What did the shop do with your rebuilt one that they took back out? Did you happen to see at least one of your transmissions after you vehicle ran and drove?

 

Ultimately they put the rebuilt tranny back in, once they determined that the old used one was acting the same way. At the time, we believed that this confirmed that the problem was not transmission related, because the odds of throwing an old used one in, and having it exhibit the exact same shifting problem was off the charts. Had to be something else causing the problem...or so we thought. I did not see any of this with my own eyes, except that I dropped the valve body out later to inspect the date codes.

The transmission that’s in the car now is the one that was rebuilt. I believed it was rebuilt because the clunk is gone, and because the date codes on the valve body and conductor plate are recent. That being said, I am starting to question whether the valve body and solenoids were actually replaced, or if a date was just etched into the surface of my original ones, and reused.

I don’t know what to think. I might get a used TCM and throw in there because they’re less than $100. Supposedly the shop did a TCM swap too, to eliminate that possibility. But if I’m prepared to believe that ONE shortcut was taken, then I have to be prepared to believe that lots of them were taken.

I’m at a loss.

Edit to add: Before and after I dropped the valve body out to satisfy my curiosity about the rebuild, I also ran resistance and continuity tests on all of the pins/wires running between the transmission and the TCM. All of those pinpoint tests checked out perfectly. Although those tests include resistance in the solenoids, I also conducted resistance tests of the solenoids themselves when I had the valve body out. All tested perfect.

 

You said this shop that rebuilt your transmission had a used one on hand. Did you physically see this used transmission? Is this a Jaguar repair shop or just a transmission repair shop? You know where I’m going with this right?

 

It is an independent Jag shop, and I did not see the used transmission. The transmission was from a non-running XJR owned by the shop. I didn’t see that car either, but at the time, I had no reason to question anything. The Jag shop removed and replaced my transmission, and a transmission shop actually did the rebuild.

Yeah I know where you’re going, and I’m starting to go there too. I’m now revisiting everything I have been assuming about the rebuild process, and I’m putting everything back on the table. I’m not going to make any accusations until I know what the problem is (if I ever solve it). The shop has been in business with the same owner for many years, so I hesitate to believe they are dishonest. But like I said, everything is on the table at this point. Only way to tell will be when or if we solve the problem. At that point, I will look at my options.

One other thing I thought of: the valve body bolts up to the transmission body. What if the mating surface is cracked or warped on the transmission body? Replacing the valve body may not fix the problem. Not sure how to know unless it’s visibly cracked....hmmm. Just thinking out loud.

 

Just thought of a very basic thing to check - the fluid level (maybe you have already checked it). This transmission is very sensitive to fluid level and, if overfilled, this will cause some loss of fluid pressure due to fluid foaming and, consequently, shifting issues. Depending on the amount of overfill, the transmission may exhibit shifting problem only when the fluid heats-up to an extent when its level rises to a point where it starts foaming.

In case you don't have it, I attach the 722.6 Service Manual (which also includes the fluid level checking procedure), split into 3 parts due to size.

 

Hmmm. I have indeed checked the fluid numerous times, but since everything is on the table here, I am going to revisit the fluid level question again. Not long after I got the car, I bought a dipstick and checked the fluid. It was low, so I added fluid. Some time after that I drove it to Phoenix, which is when this problem first arose. Some time later, as I tried to solve the shifting issue, I drained and replaced the fluid and filter along with the pan gasket. It is possible that the whole time I either a) do not have the correct dipstick, b) am not using it correctly, c) misinterpreted the levels I was seeing, or d) the fluid temp was too low when I assumed it was “hot”, causing me to overfill it.

Until you asked this question, I have never considered that the fluid level was not correct. I believed that I had been careful about the fluid level, but I will definitely revisit this.

A quick question: when I insert the dipstick, it goes down and then stops when (I assume) it hits the bottom. Is that right, or have I been doing it wrong the entire time? I believe I have followed the procedure correctly, but I want to start with this.

Thank you!

 

I checked my level (after filter and fluid replacement) when the engine (and transmission) were cold. This was about 30C (the ambient) in my case. I started the engine and quickly moved the shifter through the gears then I checked the level. I used the graduation on the dipstick corresponding to about 35-40C to allow for some transmission warm-up during the checking time. You have to check a few times, wiping the dipstick very well, to make sure what you are seeing is the actual level.

The dipstick should be inserted until it hits the bottom of the sump. I think I first did the insertion with the sump empty so that I could hear a clear "bonk" meaning that the dipstick really hit the bottom. Then I put a mark on the dipstick against the top of the dipstick tube. I remember that the insertion of the dipstick was not very smooth - it would temporarily catch somewhere and I hat to rotate it to continue. I also remember that the last "catch" point was somewhere about an inch or so before hitting the bottom which I overcame by rotating and pushing the dipstick slightly harder. So, you really have to take care to make sure the dipstick has bottomed out.

On my Super V8 transmission (same as the XJR's one but I am not sure whether the dipstick tubes are the same length), my mark for the top of the dipstick tube is at 704 mm from the tip of the dipstick. The picture below (yellow line) shows where the plug on my dipstick tube is sitting in relation to the engine centre cover (jut below it) so, if the plug on your car is at about the same position, it means that the lengths of the dipstick tubes are same. In that case, you can put a mark on your dipstick at 704 mm and see whether, when you insert it, you get the mark aligned with the top of the tube. You can do this check without starting the engine - the fluid level will be quite high but you just ignore it.

 

This is extremely helpful - thank you. I am familiar with everything you pointed out here, and it all sounds like what I've experienced. When I pull the dipstick out, I always have to futz with it a little bit, turn it a little, before it will come out. But I will revisit this entire line of thinking and double check everything I've been assuming regarding fluid level.

I hope it's this simple, but I would sure feel stupid . I am also second guessing what I've been assuming was "hot enough" for a hot fluid check. We'll see what I find...

Edit: I will measure the dipstick to the top of the tube. The tube on my car appears to be exactly the same height you show. If it's significantly different than 704 millimeters, I may have to regroup. But I'll check that first.