When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
i’ve been enduring an ongoing nightmare with my 96 XK8, 140k miles. I wanted to rectify an issue with the JGate positions not illuminating when the shifter is placed in gear. I’ve read far to many forums and threads on this subject but nothing exactly pin pointed it down for me.
To start with:
P is not illuminated. R & N will select & illuminate as selected. When placed in D, the LED doesn’t illuminate unless I move the shifter halfway between D & 4 or if the cable in gently nudged backwards.
Shift over to manual side and gears all select 4,3,2, but shifting back from 3-4, 4 will not illuminate and error code comes along when shifting from 4-D (thinks it’s still in 3rd & missing 4).
no matter how much I adjusted the cable in the car and under at the gearbox I couldn’t get all gear positions to illuminate when selected. The best I can get is all positions without P however I have to nudge the shifter to get D to light up. If I remove the JGate fascia (LED position faceplate) and shift gears each gear illuminates correctly in each position. So it is as if the cable travel needs to be shortened to operate with the JGate fascia in place since the shifter travels slightly less.
i do have videos showing what I’m explaining, not sure if they will upload. Anyway.
so I ordered a new shift cable thinking that was my problem. No joy. Issue still persisted. So I returned the cable.
after many more hours of adjusting I thought that the JGate had excessive play in the white slide block. I did discover that the slide block is discontinued by jaguar for the early models so I got a replacement JGate. I do feel a slight improvement with the replacement j gate but still hasn’t rectified anything.
so I disconnected the rotary switch and resistance tested the switches following the jaguar procedure that’s floating around one of the million forums I’ve been reading (I think I’ve read them all!) all switches open and closed as the procedure states except when testing SWL2, shifting from 3-4 resistance remained at 0.4ohms instead of 0 but testing SWL1, shifting from 3-4 the switch behaves as it should. Does this indicate the rotary switch is bad? I also noted on testing the P & N switch opened and closed as it should but that doesn’t explain why I’ve occasionally had issues with no start in P but starts straight up in N.
so I have kind of ruled out the rotary switch. Which just leaves me back to suspecting the cable adjustment again. Perhaps a new cable to go with the new JGate?
This has gone on far too long now. Next step is to set fire to it then push it down into the river.
I hope anyone can follow this and any help or advice will be massively appreciated.
Had that problem, been in there and somehow fixed it
Matt,
I’ve had your problems when I initially got my 1999 XK8. Used my scrap donor car parts, twice in there, to eventually fix it.
Firstly, found coffee stains inside the J Gate module. We all know how ineffective the cup holders are in the arm rest. Had to clean the little PCB off and checked all the bulbs worked. The J Gate module had a gasket under the face plate that broke and was restricting movement of the heat lever.
Some J Gate lights wouldn’t come on but car drove fine. Had the P-N start problem too. That wasn’t the J Gate module but the small microswitches located under it, on the mounting bracket.
Then the cable needed adjusting. It was a very fine adjustment but there’s a screw there which seemed to move, so second time in I put thread locker on it. My problems seemed to go away.
Just to clarify if I remove the j gate LED module (top faceplate with positions) all gears select and illuminate. If I place the LED module faceplate back on, positions don’t illuminate and there feels like play.
what also confuses me is when I tested the rotary switch the switches made as if D should be illuminated. I am correct in saying that the rotary switch tells the LED module what position it’s in?
also David I only purchased the mechanical section of the J Gate. So led module is still original.
Spending on cable adjustment only a certain combination of positions to illuminate
Last edited by matt0091; Jan 15, 2020 at 03:55 AM.
So your J Gate lights seems to work 100% without the top face plate cover on. Car drives fine and transmission shifting without issue. Hmmmm, there's nothing special in the plastic top cover plate.
I seem to remember the PCB, with the LED lights, is located in the middle cavity centered on a few pins. Is this PCB sitting incorrectly? It's not bent/forced in any way by the display mount above. Once the J Gate module is in place, with the top face plate cover on, I would first look for some PCB/cable pinching/impediment between the display mount/PCB/wires/connector pins.
i won’t rule it out but I think the top led module is fine. Nothing suspicious looking on it. Also the fact that it lights up all positions when it’s removed.
I think the No start in park is related the shifter/ cable position cause when I place it in park the led doesn’t light up however if I push the cable forwards or pull the lever at the gearbox there is about 1mm movement which brings the park light on.
but then sometimes it still starts in P while the light is out.
I was just under the car looking at the link at the gearbox. Suspecting the ball joint may be a factor here. I Applied a tie wrap to restrict movement in the ball joint, made a cable adjustment and I can now cycle and select all gears (D now just needs a slight move to the left of the shifter) however P still won’t light unless I give the cable a nudge. And all gear actually engage and moves forwards and backwards.
so I’ll see if I can source a new ball joint for the gearbox end of the cable.
When I was fiddling about with it this morning the no start in P issue arose. So I tested the rotary switch at the connector at terminals J & K in the wiring diagram for P/N and the switch had not made contact. So I went under the car and the gear lever had slight movement into park, checked the multi-meter and the switch made contact.
It get a picture but it’s not the original ball joint as I had an idiot moment and broke the thread of the original. But the original had loads of play and issues still persisted
I am correct in saying that the rotary switch tells the LED module what position it’s in?
The switches inform the TCM what position the stick is in. Then the TCM sends software messages over the CAN bus to the illumination module to tell it what LED to turn on and off. There is no conventional direct wiring between the switches and the LEDs.
The switches inform the TCM what position the stick is in. Then the TCM sends software messages over the CAN bus to the illumination module to tell it what LED to turn on and off. There is no conventional direct wiring between the switches and the LEDs.
This is the reason I was asking about the lights working vs the transmission shifting into gear. If the shifter light is off, for example, in D, but the car shifts into gear, that may suggest illumination module wiring.
When you say the lights work with the gear module off, what does that mean? Are you manually pressing the switches, rotating the flat follower, etc? If so, based on the behavior, it looks a bit like spotty engagement of SWL1 (P not lit, P sometimes doesn't start, starts in N, D not lit, 4 not lit) or spotty pulling on module wiring (that crappy edge connector badly soldered to the illumination module board) in various positions. As partially noted above, seems like this could happen from 1. spotty switch, 2. spotty switch support, 3. fine details of cable adjustment, 4. badly soldered connectors on board. 1-3 more likely than 4? Perhaps.
Just as an aside, the CAN signals for the J-Gate can be read from the CAN stream (CAN Gear Position Selected) in the unlikely event you have the right oscilloscope or a sniffer.
ID 0x3E8h (or 3Eh hex) byte 1 bits 5-8 4 bits (most significant hex nibble-big endian order), Park - 0000, Reverse - 0001, Neutral - 0010, Drive - 0011, Gear 4 - 0100, Gear 3 - 0101, Gear 2- 0110, (intermediates 0111).
There is also CAN Gear Position Actual, but that involves the TCM making decisions potentially countermanding your gear selections (e.g. make the bad decision of 2 when going 100 kph) and does not involve the J-Gate lights.
If all lights are working when you have the cover off, and the park position light only works when you nudge the lever with the cover on, it sure sounds like you have a misadjustment problem. Most likely the cover is restricting the movement of the lever into the park position.
[QUOTE=crbass;2179161]This is the reason I was asking about the lights working vs the transmission shifting into gear. If the shifter light is off, for example, in D, but the car shifts into gear, that may suggest illumination module wiring.
When you say the lights work with the gear module off, what does that mean? Are you manually pressing the switches, rotating the flat follower, etc? If so, based on the behavior, it looks a bit like spotty engagement of SWL1 (P not lit, P sometimes doesn't start, starts in N, D not lit, 4 not lit) or spotty pulling on module wiring (that crappy edge connector badly soldered to the illumination module board) in various positions. As partially noted above, seems like this could happen from 1. spotty switch, 2. spotty switch support, 3. fine details of cable adjustment, 4. badly soldered connectors on board. 1-3 more likely than 4? Perhaps.
The car shifts into each gear even if the position doesn’t illuminate, so going on what you mentioned it’s worth looking into the module wiring.
I did make a video of what I describe but can’t seem to upload it. Unscrew x4 screws on JGate top LED module. Lift it up over the shift stick. Shift through P,N,R,D, turn the circular plate round to engage the D-4 switch, then shift to 4,3,2 and back to P disengaging the D-4 switch When passing back to D.
If SWL1 wasn’t engaging correctly I would be right in saying that I need a new rotary switch?
I’ll test the rotary switch again in the morning just for peace of mind.
The car shifts into each gear even if the position doesn’t illuminate, so going on what you mentioned it’s worth looking into the module wiring.
I did make a video of what I describe but can’t seem to upload it. Unscrew x4 screws on JGate top LED module. Lift it up over the shift stick. Shift through P,N,R,D, turn the circular plate round to engage the D-4 switch, then shift to 4,3,2 and back to P disengaging the D-4 switch When passing back to D.
If SWL1 wasn’t engaging correctly I would be right in saying that I need a new rotary switch?
I’ll test the rotary switch again in the morning just for peace of mind.
Great, appreciate it, understand.
With the j-gate cover off, the stick has an increased range of motion, especially towards P, as you probably noticed. The module gasket stops the stick moving forward and to the right from the P position when it's in place. Since putting the stick forward of the nominal P position (module cover off) causes P to be lit, seems like the cable should be readjusted so that it is a bit shorter than now to bring the shifter position and the rotary switch into better alignment.
It's still a bit mystifying why the transmission shifts into gear since the CAN bus apparently doesn't think that gear is selected (thus lighting the module), so...
...all that said, while you have everything disassembled, you might want to take the illumination module board out anyway, resolder the edge connections, thus removing uncertainty about lighting the module, and replace the two incandescent bulbs that provide j-gate backlighting (if they are burnt out). Those are soldered on the board. I've done this for all of mine.
J Gate positions
