I don’t need a new or rebuilt transmission!
I will pay for the diagnostic work (1 hour)
Mechanic recommends I track mileage & cumulative drive time from when I depart his shop & let him know exact milage & cumulative drive time when/if Transmission fault reappears. He expects it to reappear @ 59 minutes.
IDK why.
When/if it occurs again, he offered a used TCM for $250 part + labor (He says he has several of these from XJ8s in his shop)
I may seriously consider DIY if I can get one for $50 & see exactly how I would swap them out. I will need to learn HOW I clean the connector as Lady Penelope says. Maybe find a video or a photo how to post in this forum.

Rather than pick up the car Wed, I had then flush the coolant, which is overdue.
I pick it up Thursday. I was actually about to arrange coolant flush when this Transmission problem occurred.

I’m taking my own thread off topic!

I may look into selling the car, once the TCM is replaced.
Down to 4mm Front brakes (just had front brakes done @ dealer 8k miles ago!)
At the time, I had only 21k on the F brakes & was unhappy since I got 30k the 1st 2 x I had to do F brakes. I went over & over this with my Jag dealer SA & the mechanic & he showed me the brakes & he insisted the calipers were not hanging up & no need to rebuild & he cleaned & lubricated “everything.”

I will need to replace the @#**&!! Brake switch a 2nd time. Had done @ dealer in 2012.

I have a small oil leak in the oil pan gasket. I may try to DIY.
Will see if my jack stands give me enough room. Will buy a small torque wrench.
I have the diagram with the tightening sequence & instructions from this:

https://www.jaguarforums.com/forum/x...ket-xj8-76458/

Since last year when I cleared codes after replacing another ignition coil (5th one replaced; dealer did 1st one, $$$$$ & I did 2nd-5th, …easy!) I did the drive cycle many times & got all the self diagnostic tests to run except “CAT!” So, may have problem with my catalytic converter.

 

I forgot to post that the actual code they found yesterday was: “1605 Transmission Control Module Checksum Failure.”

I picked up car today! They only drove it 4 miles to test. So looks like I paid 1 hour labor ($110) for them to read the codes & drive it 4 miles. Does that seem reasonable? It is important to me, bc now I know about the TCM & that it is not a mechanical problem with the transmission.

But does it typically take an hour labor to read the codes. My guess, based on how long it takes me to read Check Engine codes with OBD-II, is ~10 minutes tops, maybe add 10 minutes for a short test drive. I doubt total time spent was > ˝ hour. Am I wrong? Does it take most of 1 hour technician time to read transmission codes?

I asked why they want me to take the car (un-repaired) & log & report back on time & mileage as I drive to note if/when it happens again. They made it clear that it may not happen again. They used computer example saying that your computer may do something strange & you restart & it never does that again. As I have said several times, I am not a mechanic. If the owner & shop Forman turn down the opportunity to make $360+ ($250 part + 1 hr. labor) by replacing the TCM with one of their used, salvaged TCMs, they must have a good reason & are acting in my interest.

I drove off @ 5PM in time for rush hour traffic. Car drove normally, as it did when I drove it to the shop Tuesday night to leave it, so they could test it cold. I was thinking that it will do this Transmission fault again in a week or a month…I was wrong.

˝ hr. Later, after driving normally 8 miles, I was idling for 5 minutes in the fast food drive through lane. TRANSMISSION FAULT - AMBER LIGHT ON!
I shut car off & restated & as b4, no help, Error immediately appeared. So, I drive the remaining 7 miles home, stuck in 4th gear.

So, I am seriously thinking of buying a used TCM & DIY.

I know I need to look at mine & get the numbers off it & get the replacement with the same #s. Or at least some of the #s must be the same. Any web sites that are reputable where I should shop for my TCM? Does any seller test them, refurbish them? Or am I taking a chance in buying one, installing it & it gives me the same error or a different transmission error due to the replacement also being defective?

Any links to instructions or a video for the replacement procedure?
I know it is located under the hood, passenger side close to the windshield. I must remove the plastic cover (Is there a technique or do I just pull it straight up? Then I think I find a waterproof box that I must get into in order to see the TCM to read the #s.
A video or photos with instructions step by step would be very useful. I think I need to disconnect my battery negative Cable b4 I actually remove the old TCM & replace it. I should clean (how?) the connection when I remove. Is it a wire harness? I twist but, not too hard & then pull apart?

I guess after I replace the TCM, the code will not go away unless I clear it. I am sure I cannot clear it the way I clear CEL using OBD-II.
Do I clear it by doing hard reset with the battery, per RJ237 post?

So,

*Where do I buy TCM
*Link to instruction with photos/video
* Clear code

Thanks!

 

A check sum failure is like a heartbeat failure in that the ECU does not complete a computation as it double checks itself not related to sensor values or bad solenoids . That is a general understanding different then the specifics of this example ECU

The transmission ECU on the similar X300 is on the very bottom of the passenger side exposed as you looking under there. The X300 has a long connector . The X300 is a Bosch brand unit .

 

Best I can find is for 1998 XK8:

https://www.justanswer.com/jaguar/78...-tcm-used.html

Also, instead of buying a used TCM, what about sending mine to ASI?

 

"I tested Voltage @ the battery with a multimeter just in case it was a bad battery causing this transmission fault message.
12.45 V, so ~ 80%, surprising since I just drove the car day b4 for ~ ˝ hour each way.
I charged it overnight with my CTEK MUS 4.3 using the normal (14.4V setting) The battery has a sticker that says to charge @ this voltage. (I know some other AGM batteries need to be charged @ 14.7V, cold weather program)
Now Battery @ 13.22 V, excellent charge!

Sadly, still have transmission fault. I have not driven it, just turned engine on to see if fault would go away after charging battery fully.

Unless I have this completely wrong once you charged the battery and you started it would take a while for any unreadable trans codes to go away. Something like you have to drive through couple cycles or so. Or do a reset. So once you took it out to drive you probably completed the cycle. Then when you drove to mechanic it had "reset". I would still have the battery checked. New or not? I can confirm these cars so rely on correct voltage.

 

Iconoclast: It's an old car .. stuff fails. Intermittent problems are annoying and difficult to work through sometimes. The cars are now at the bottom of the value cycle. It is what it is.

It becomes a question of what are you using the car for. Both of my XJR's are for occasional use -- while they are both still reliable and I have no problem driving them back to the city occasionally .. I don't use them as daily drivers .. and no longer take them on trips. I need something at the houses .. it's good fit. You can't really do a cost analysis on each repair .. it's really about alternatives ...and those costs.

25k out of front pads is about right .. the dealers are often a bit quick to switch them out basted on 15k miles a year. I can't remember if the new pads are 9 or 11. If 9 you are a bit past 1/2. All all the pads the same ? If so what's going on with the rears -- do the rotors look clean. Maybe something else going on. Most shops charge an hour labor for any kind of diagnostic -- look what you got for $110 bucks .. his knowledge. That you now want to use in another way.

The brake switch and pedal assembly was an issue in some early vehicles -- there is a TSB. I would clear and see when that one comes back. Also -- aftermarket valve cover gaskets have a history of leaking.

Sometimes it's a question of a good guess ... let's try this before we rebuild the transmission.

 

Larney, good points, the mechanic says they load tested my battery & it was good, 100%. Said only dropped to 11.53 V when cranking.

Have not taken car on a drive since returned from mechanic with the Transmission fault code having returned & car stuck in 4th gear.
I did pull car FW & adjust position in my garage so I could get to the TCM. The code is gone & probably have all 4 of my gears back, for a while (maybe 5-10 miles? Not going to drive it till I fix TCM. Don’t want to damage transmission by starting in 4th gear. Mechanic said very high pressure when do this.

yeldogt, I had been driving my Jag 1-2x/week. I use my other much newer car more, 3-5x/wk. My front brake pads had 12mm when new per the mechanic & they were done @ the dealer with Jaguar factory parts. so, I have used up ⅔ in 8k miles. If I still have the car in 1 year I will deal with the brake issue. Something is amiss. I didn’t change my driving style. I do not like the idea of new front brakes every 10k miles.

Yes, it was worth $110 to me to know about the TCM & the exact error code. I wish the mechanic had test driven it more than 4 miles! Hardly seems sufficient to see if the issue reoccurs. In fact when I left I only got 8 miles b4 it happened again.

I will do absolutely nothing re brake switch now. I have NOT had a brake error message. A few years ago, when I did, it was a problem with cruise control not working & I think I would get “ASC not available - Trac not available" messages. I will review my notes from back then & if it happens again will either pay a mechanic to replace the brake switch or revisit the DIY thread & see what the new switch will cost me & see if I can find a helper or maybe come up with a creative way to do it by myself. Maybe start by cramming myself in the driver foot well & seeing how difficult it is to reach it. Probably had not become easier as I’ve aged!

I jacked the car up higher than when I change oil & looked at the oil pan. I can’t see any leak now. I can reach most of the bolts & think I would need to remove the fiber cover since it may be blocking a few. No more oil drops on my cardboard!

I bought a ˝ inch drive torque wrench. I will revisit the oil leak when I fix the TCM. I will fix TCM & oil leak even if I end up selling the car. I would prefer to sell it to a Jaguar enthusiast who will drive it & enjoy it rather than sell it for scrap. The body & interior are in superb condition.

I am going to start a TCM thread with photos & ask my TCM questions there.
I took pix of disassembly (Easy) to get to the TCM. I will title it:”Transmission Control Module - replacement.” Once I get the replacement TCM, I will take more pix & detail exactly how I removed it.

Thanks!

Steve

 

I mentioned this issue in the Forum a few weeks ago.
We replaced the transmission control module and so far ....no problems.
I will continue to drive it and see what happens.
Thanks all that sent in input.