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I have P1643 on my NA jaguar xj8 4.2L cant find the TCM anywhere! heard it might be on the trans case itself, huge engine power loss, rpm bounces when i gas it and no power flows through gears, from 0 to throttle its super slow and weak. in park engine runs just fine, (except the restricted performance) but its not losing power like when im in drive. also I did just refill the transmission fluid.
note i also have a system lean code and knock sensor high input code.
how do i fix this cheaply, i can do the work myself but where is the TCM?
Link to video of how the car is acting right now
~~~~~~~>. https://youtu.be/Icn6vBHKQf4
another side note the pcv valve after two used ones and one remanned (current one) are snapping in the same spot. i suspect might be my problem but the rpms not going tgrough my gears doesnt make sense even with a vaccum leak... (picture below)
Last edited by Tony_Likes_Going_Fast_XJ8; 12-27-2022 at 04:53 PM.
So ive learned to pump transmission fluid into the fill bolt it til it starts spilling out with the car off, and than repeat with the car on?
so if the TCM were to need to be replaced, is there anyway of doing so without removing the entire tranny?
Nope there is a little more to the fill up than what you just wrote
yes fill up till it runs out . Car has got to be level
start engine continue to fill up go through all the positions of the shifter / transmission ,let the engine run so the oil is getting everywhere until transmission oil has 40 degrees celsius/ 100F . If the oil still dribbles out the fillerhole it is at correct level.
One other point is to check the sealing sleeve as just about 100% of the ZF 6 speeds will have a leak at this spot. Only can be changed after dropping the pan and it's cheap. So if you do decide to do a complete service and change the filter/pan as Xalty posted plan on replacing this as well.
Be aware that if you have the fill plug open without the car running fluid will pour out and you will be low on transmission fluid. As posted above the fluid fill and check procedure is a dynamic one that HAS to be done while the car is running and the fluid is in the correct temperature range.
One addition tip from experience is PLEASE loosen the fill plug BEFORE you drop the pan and drain the fluid. For some reason ZF installed this plug with a BFH!
It's also hard to get too and I cut down an 8mm 90 degree Allen wrench AND used a 1.5' cheater pipe on that small 8mm Allen wrench. When it let go it threw the cheater and the Allen wrench completely off the fill plug. Since this is a nice O-ring fill plug I don't understand why the need to tighten this plug so god awful tight? I reinstalled mine with a slight bit of torque by hand and nothing more.
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So are we assuming that my problem is due to low transmission fluid ? Yall did see the video i linked to how it was acting right? and the transmission code P1643?
No we don't know that at all. You have an error code and there is something causing it.
BUT the first step in troubleshooting is a fluid check. Until we know the fluid level is right or not many things can be possible.
But let's do the simple stuff first as we know low fluid level will cause all kinds of problems and codes.
In fact before I did anything I would do a complete service. Pan/filter + fluid change. Remember these are now old cars and any new fluid will be a good idea.
We have not mentioned this yet but you can use Lifeguard6 or Mercon SP as they are identical fluids except the Mercon is red in color.
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If you swap out a TCM without OEM Jaguar SDD software and the OEM Mongoose interface to RE-FLASH the new TCM to the vehicle you will be completely dead in the water. Try everything else first.
P1643 can be caused by a misfire. Instead of firing the spark plug, the high voltage spike propagates through the electrical wiring and can reset either the TCM or the ECM. During the reset period the other modules on the CAN network set codes because the affected module is offline momentarily. First I would make sure that your battery is in perfect condition and producing at least 12.3 V at the terminals. Low voltage will cause many seemingly unrelated problems. Then, attempt to re-set the system by cycling the key on and off TWICE. The first cycle will reset the Gearbox fault condition and the second cycle will reset the restricted performance. The reason your car wont rev in neutral AND has low power is because the "maximum throttle opening for N range is inhibited" and "Throttle opening is limited to 30%" during a P1643 (and lots of other codes). After you re-set with the key, (and fix the obvious PCV problem) clear the codes and then attempt to drive gently. If you feel the engine shuddering then you first need to address the misfire, and or lean condition. In my opinion, the P1643 is most likely caused by other problems not an actual CAN bus malfunction.
P1643 can be caused by a misfire. Instead of firing the spark plug, the high voltage spike propagates through the electrical wiring and can reset either the TCM or the ECM. During the reset period the other modules on the CAN network set codes because the affected module is offline momentarily. First I would make sure that your battery is in perfect condition and producing at least 12.3 V at the terminals. Low voltage will cause many seemingly unrelated problems. Then, attempt to re-set the system by cycling the key on and off TWICE. The first cycle will reset the Gearbox fault condition and the second cycle will reset the restricted performance. The reason your car wont rev in neutral AND has low power is because the "maximum throttle opening for N range is inhibited" and "Throttle opening is limited to 30%" during a P1643 (and lots of other codes). After you re-set with the key, (and fix the obvious PCV problem) clear the codes and then attempt to drive gently. If you feel the engine shuddering then you first need to address the misfire, and or lean condition. In my opinion, the P1643 is most likely caused by other problems not an actual CAN bus malfunction.
To add on Jeff's feedback, a simple check would be:
Check the wiring harness going into the back of the trans. Is the bottom wet w/ trans fluid? If so. Bingo - you found your problem.
Second, remove the harness (disconnect battery) and check the pins and interior harness for trans fluid ingress. If any evidence - you need to swap out that mechatronic seal w/ newest version (black o rings) which means pan/fluid drop.
The replacement sleeve is a PITA to get back in. Many say lube the o rings w/ trans fluid. Personally I use plumbers o ring lube.
You also need a 2 × 4 and a crow bar to place even pressure when inserting. Also, there needs to be a measurement of 2mm to 3mm from the harness (when plugged back in) to trans case.
It is possible to see a 4mm - 4.5mm measurement and the tab in the case will engage the mechatronic sleeve but the pins will not be fully seated into the harness causing a variety of issues and a re-drain/refill can be costly - both money and time.
Again, not for the faint of heart but lots of good tutorials out there.
Best advice:
Use ZF genuine parts, especially the pan.
Either LG6 or Mercon SP fluid - nothing else.
Proper measurements and vehicle being level at the frame are key...
Original Zf numbers
1068.298.090 Inner seals mechatronic, bridge, sleeve
1068.298.062 pan filter oil screws magnets
if you have an oil leak at the electrical connector you would have to open anyway.
i "cycled" the key on & off, but the restricted performance light stays on. only when i erase DTC codes does it go away but comes back after running @JCalhoun ( i reset once i replaced PCV)
im currently going down the proccess of elimination list now, results will post soon...
If you swap out a TCM without OEM Jaguar SDD software and the OEM Mongoose interface to RE-FLASH the new TCM to the vehicle you will be completely dead in the water. Try everything else first.
tcm has no vid info
as long as the calibration is close enough it’s running period end of story
Update !
Alright so I'm back and I've completed I believe all of your requests
list:Jaguar Check List
In Order 1-
Check Battery Volts ✅ (12.6v 100% charge)
Re-set system 🤷🏽♂️ (i think so?)
PCV valve ✅
Check wiring harness for wetness✅
Complete Trans Flush✅
Clear codes drive gently✅
and nope, drove gently after clearing codes and immediately (knock sensor bank 1 high) came on and i would throttle and the rpms would rev up (like as if in nuetral for a sec) but no actual thrust to wheels.
BUT!
once i finished the trans fluid fill and put it in drive, & reverse i noticed that only one wheel (the right) was spinning like normal but the left wheel wasnt spinning like AT ALL. unless i pushed the gas and even then it kinda struggled.
Happy new year from Luxembourg . Hope to help resolve the problem .
so you had the car in the air and running idle . Only one side turned in idle rpm .
I currently have some issues coming from the back wheel bearings I believe .or
the brake sliding pins have to get cleaned regreased or either changed .
when driving around my back wheels are getting some higher temp. Than the ones infron
Tony we need the actual code numbers. Now you mention a knock sensor? This is new? Again what is the exact code?
Was the car jacked up in the air? How did you tell one wheel was moving but the other was not? Your car has an open differential so the rear tires will always turn independently. Maybe I am reading what you wrote wrong? Forget the differential that's not your problem. Or is the transmission slipping? Which again leads back to proper fluid level.
Are you getting any transmission codes?
Battery voltage resting and running?
Reset what system? Post codes these tell the story. So far the only code you have posted was P1643 is this gone and are there other codes now?
After the trans flush was the fluid level set correctly. What temperature was the trans fluid. What trans fluid did you use? What did the old fluid look like? Any pictures?
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12-27-2022, 03:29 PM
2004 Jaguar XJ8 4.2L NA P1643
and nope, drove gently after clearing codes and immediately (knock sensor bank 1 high) came on and i would throttle and the rpms would rev up (like as if in nuetral for a sec) but no actual thrust to wheels.