I am sure it is a real possibility that this could still be the case! but then if it were me looking in reading this i would take the stance not to comment unless it was something constructive or helpful? Just the way i think i guess

 

Did you also have the same short between CAN+ and battery power? This seems like an exceedingly rare fault. Whenever I encounter something so far out of the ordinary, I've learned the hard way to always review how I got there.

I'm seeing only two possible causes. One of the modules in that daisy chain has an internal short, or two wires have rubbed together somewhere in the harness. Considering the previous mention of how some of the faults cleared after cleaning up a crusty ground, I'm hoping for the latter. Just a guess, but that ground may have been okay and the partial improvement came after moving the harness during the cleaning.

For now, I'd suggest hooking up the meter again at the diagnostic connector. Shake down the harness near that suspect ground and see if the reading changes.

If no change, try isolating that CAN circuit into segments. See if the short goes away. Look at that figure 20.1 to see all the components between the TCM (on the left) and the diagnostic connector (on the right). Disconnect a connector or component somewhere near the middle, whichever is easiest to access.

If no change, undo a connector or component closer to the diagnostic connector (and meter). Keep moving closer to the meter until the short is gone. When you do see a change, reconnect everything and then disconnect the next connector or component away from the meter. Keep working back and forth and you should be able to isolate the fault between two adjacent points.

Keep in mind you're in uncharted waters here. The pinpoint tests gave some very specific tests to determine you have this ultra rate fault. Then it gives absolutely no further instructions of how to isolate the location.

 

IIRC I had a can positive short . which showed from the OBD2 port .
. Pin out testing between the ABS module connector and the ECM ,
with the TCM plugged in showed a short also .
Same test with the TCM unplugged showed no short .

this short also took out some components in the cluster CAN control circuit
. It was not expensive to repair .
$180 if I recall .
Iirc The ABS module repeats on the canbus circuit. I.e 2wires in 2wires out .
Were as the TCM and ECM are daisy chained . Same two wires.
but as you said with the revision cluster in 2005 some of the can-bus control circuit is changed.
Mine is 03.

also seperate incident, I have had my transmission wiring loom pinched by the Bell housing when engine mount failed .
so it’s worth a good look around that area as well.

 

One more thing you can check. I’d do this first, just because it’s so easy.

Hook up your meter again at the diagnostic port, to measure resistance between CAN+ and battery power.

On the wiring diagram figure 20.1, follow the circuit supplying battery power to the diagnostic port. You will see a fuse in the primary junction box, inside the cabin by the US front passenger’s feet. (Sorry I can’t give you a fuse number, but I can’t view that huge PDF on my phone.)

Pull this fuse, and see if the meter reading changes.

 

Ok so checked off the fuse 6 in primary box against test E3 and with fuse it registered over 2k resistance then drop to 1 and with fuse 6 removed it measured 1. Not sure what this means karl but possibly intermitent fault maybe

 

Sorry for the late reply. Was scheduled for some Mandatory Family Fun yesterday.

The latest results have me confused. I will have to put on my orthopedic thinking cap for this one.

Please confirm the battery ground cable was disconnected for that test. If not, that could skew the results.

Just for giggles, what if you tried starting the engine with that fuse removed? I think it only supplies battery power to the diagnostic connector. It should not affect anything else.

Have you tried testing with anything disconnected yet? Previously I had suggested breaking the long daisy chain somewhere in the middle. Now I’m wondering if it might make more sense to disconnect the TCM first, since that is the module acting up. I know the TCM is inside the transmission, but is there an external connector that can be accessed without too much trouble?

Anybody else have any ideas? Am I the only one brave/foolish enough?

 

No dont apologise Karl! it is great your mad enough to apply some knowledge i dont have lol On the E tests it says to disconnect the battery negative terminal? Got me wondering now if thats a mistake,, As far as the tcm the only connector is the 16 pin round connector to the trans under the car so that will do but im sure although i havnt found it yet there is another connector on the other end connecting to the engine loom unless it is spliced in from factory which will mean unwrapping it. Either way its not gonna be easy but if i dont do it then the cars just a brick!! bloody crazy electronics

 

No, the battery should be disconnected for any continuity tests.

If checking for voltage, obviously the battery should be connected. But not for checking resistance.

 

Have managed to source another loom complete from a working breaker so looking to remove my own and try the new one unless i find an obvious fault! at least i can then test modules if that fails to sort it out.

 

Any progress? Replacing a wiring harness is quite the undertaking. It's way more work than I'd want to do without first knowing the existing harness was bad.

Do you still have the 1 ohm reading between CAN+ and the battery, as measured from the diagnostic connector port? If so, I'd suggest concentrating on that for now.

If the fault is still consistent, try removing the 250A megafuse at the rear power distribution box. Not positive about the location, but I believe it's on the side of that panel. This will isolate all direct battery circuits at the rear power distribution box and also the primary junction box inside the cabin. If that 1 ohm reading now returns to normal (I forget the expected value if all is good, greater than 5 ohms?), then you'd know one of those many circuits is at fault. You could reinstall the megafuse and then pull the individual fuses one at a time.

If this fault is still there with the megafuse removed to the rear power distribution box, there's another 250A megafuse you can pull to totally isolate the front power distribution box under the hood. This one is hidden under the trunk sidewall on the right side. It's right next to 450A megafuse for the starter, as seen here:

https://www.jaguarforums.com/forum/s...-issue-230037/

 

Hi karl, Not really done much as the weathers been wet! but did get a chance to retest the problem circuit and it came back as well below 5 ohm so not sure what is happening there. Also jacked the rear end up to check the abs/speed sensor wires and got a result as when i tried to start the car by chance it turned over and fired up! gearbox fault gone and j gate red light back on for about 15 seconds then out then flickered on again then off with fault coming back? I would assume the parking brake and abs sensors are all linked at some point in the system check so may be worth closer inspection if the rain ever stops. Not sure if i jogged the wiring somewhere or not and been down this road before lol

 

Got the trans harness today but hopefully wont need it! got it cheap anyhow from a 2006 auto but dose look like more plugs on this to what i have?

 

Just an update on this issue. Today i put new rear pads in and realised the right hand rear epb lever return spring was missing? I improvised and found another spring to temporary fix plus i also tried to split the connectors above the axle with not much luck as space being too tight! so sprayed liberal amounts of contact cleaner on them anyway and inspected the abs sensor wires more carefully to find nothing no splits etc. still could be broken maybe but as light was fading reset the epb and slowly everything came back to life? Red signal light on j gate lit up even when selecting gears and all fault codes went out while ticking over except abs fault, this was induced by me anyway from when i disconnected the sensors with ignition on so deleted with code reader and so far so good. I wont count my luck until ive secured everything ive taken apart and driven it but is a good result none the less. Not sure if the abs cables or epb spring might have caused this or even worn pads but either way i think i have localised the problem to a minimum

 

So today i think i have narrowed it down to the wiring between the epb motor and the epb module or the module and the j gate and now seem to be able to start the car and drive in normal restricted performance mode as apposed to no drive!! The original fault is very intermittent now and usually non existent when first started but then shortly returns after setting off? Quite honestly this problem is sending me back and forth doubting what ive already checked to be good but one thing is whatever i have done at the rear of the car recently i.e. brake pads has relieved the non start and stuck in park issue to the point of consistency. I still think it is can bus wiring unless broken wire/s from epb motor to connector could possibly cause such fault and without taking the bloody thing out impossible to tell due to the crap location, but can test the wire from connector to epb module i would of thought.. My best bet would be module to j gate internal harness but for now have disconnected abs wires and epb connectors and cleaned them and tested the abs wires to be reading 0 resistance. Never in my life have i had this much hassle with electrics on cars, even ones a lot older.

 

Are you still getting the P1643 code, the one that steered you to finding unwanted continuity between CAN+ and battery power?

Have you tried disconnecting the parking brake module and starting the car? You'd have to make sure the parking brake is released before disconnecting the module. Looking at the CAN network in figure 20.1, the parking brake module is at the end of spoke. I think you could disconnect it without affecting anything else on the CAN bus. Of course you'd get all sorts of new faults for the parking brake, but I wonder if the other faults would clear.

For checking a section of the wiring harness, what are you testing exactly? You need to do several things for a comprehensive check. These tests are done with a harness disconnected from all components, but still installed. In theory you could do the first two tests on the workbench, but ideally the harness should be bent/twisted exactly as installed, to help catch any faults. Shake the harness while testing, in case there's an intermittent fault:

1) Check each wire individually end to end for continuity. You should only see a fraction of an ohm in resistance, meaning good continuity. Open resistance here is bad, and indicates a broke wire.

2) Check each wire for continuity to adjacent wires. This is looking for a spot where two wires have rubbed together. You should not see any continuity at all between adjacent wires. If you were getting battery voltage on CAN+, this is how you'd find it.

3) Check each wire for continuity to the chassis. (This test can't be done with the harness removed.) This is looking for any spots of the harness rubbing against ground. You should not see any continuity at all. If the harness contains a ground wire, that one would normally be grounded, but not so if fully disconnected.

 

Now solved but announced in a new thread.

https://www.jaguarforums.com/forum/s...6-auto-252892/