My Jag won't start with the J-Gate in the Park position, just turns over endlessly and shows "Engine Fault" on the display. Shift to Neutral position and it starts easily and drives normally.

This is immediately after adjusting my shift linkage to fix an issue (likely related) of the the JGate not easily engaging into D (the red D indicator would not easily illuminate), the adjustment 100% repaired that issue and it engages all gears perfectly EXCEPT for P which has not lit up in a few months now so I've got no idea if it is engaging or not, but the click of the microswitch is audible and seems to be snapping at the approximate correct spot.

(also potentially relevant to this issue) My fix was 2-fold:
- adjusted the throttle linkage to remove maybe 5-10mm of slack from the connector inside the car near the JGate (under the center console)

- sprayed degreaser inside all the JGate parts (done this several times prior) and then wiped up all the gunk, then (first time doing this) added grease to every moving part, the spring, the shift-linkage rod (and pushed some grease into the sheath), the guide rod, etc.

Maybe the grease shorted something? It is a top-quality grease for precision parts (either lithium or silicon based, don't remember)

Maybe the shift linkage adjustment is now locking out the Park position? What would the car do if you tried to start it if thinks it is between the P and R positions?

No codes other than P1000.

 

You have to be careful with that adjustment, it can cause all sorts of problems and is generally best left to a garage who knows what they're doing.
Regarding the Park not lighting up, if you look at the back of the J Gate you will see the parts I've circled in the photo. This is your park position switch, there is one for Reverse and one for Drive too by their positions. Check or replace this.
Hope This Helps.

 

I had the same problem with my 98 XJ8L it was a bad cable between the shifter and trans. We tried to adjust it but the cable was rusty and just kept jamming drove it like that all that winter. Ended up replacing it when the weather got better. My 2003 VDP has a similar problem where it starts OK in park but when you put it in D the D doesn't light up on the indicator and the car doesn't shift correctly. If I give it a little jiggle the light comes on and every thing is fine. I was told it's the electronics in the console and they might be dirty maybe something got down into it. I am going to take it apart and give it a good cleaning.

 

Stu, YOU ROCK! I could not figure out what that sensor was (the 2 mounted to the bracket were obvious) and I'm quite certain that you've identified the problem as I greased that roller-up in my lubing' process and could easily have gunked up the sensor. Is there any way to adjust/tweak the position that sets off that sensor? It appears to be controlled by the C-shape in the molded-plastic. Does it sense being in park when the sensor is depressed, or in the open-position?

John, go to a different mechanic, it is NOT an electronic issue, it is a cable-position issue and it requires remarkably precise adjustment to get it perfect - I had those issues and my adjustment fixed them perfectly. Learn from my mistake though, don't clean/grease in there unless needed...

 

I've Just realised I made a mistake! Sorry, Sorry, SORRY!!!The circled switch is NOT the park switch!!! Sorry!
I got confused, the circled switch is the switch that tells the car you've moved into 4th gear. It's activated by a raised part on the plastic disc on the bottom of the J Gate unit.
The park switch is the forward facing one on the first picture I posted. I'm just trying to find you the information you require for adjusting the cable.

 

This is from Jaguar's Factory Service Manual, hope it helps.

 

Ugh, well that 4-3-2 side of the J-gate works perfectly (tested it last night on the road), the park-position microsensor on the bracket works well enough to consistently sound the alarm when you attempt to move the shifter about 1cm away from the P position with the car off, and stop alarming when reseated - so I think that indicates that the P-engaged sensor is working. That leaves me without any ideas what could be wrong

Are there any electronic sensors for the shifter-position under the car on the transmission end?

 

The only thing for the shifter position is on the the rotary switch, which isn't adjustable. There is the multi connector but I doubt your issue is there.

 

Let's try to assess this differently, what would cause the car to only start in N, not P, and trying in P throws an engine-fault dash message with no codes.

 

Reading through jtis, it looks like the transmission reads lever position from only the rotary switch, and D-4 switch to see if it's on the 4-3-2 side. The red gear position lights are also controlled by a CAN signal, from the instrument cluster. I guess it's possible the park led is burned, or the gear illumination circuit is bad somewhere. I assumed the park microswitch was the only safety interrupt.

Maybe if the rotary switch is reading incorrectly, that's why the system won't send a signal to illuminate P, and that combined with recent adjustments is preventing starting in P?

 

Just a Monday morning thought: Did you check the cable position / lever on the gearbox before adjusting the cable inside?
I can imagine something like every gear selection 'just' falls in place, but not the ultimate one at the end (which is P).
I can imagine (but only guessing here) there is a gearbox switch as well checking positions, which could throw the error.

 

Nilanium, the 4-3-2 side of the JGate operates perfectly to gear-limit (tested on the road) and illuminate the gear, so the rotary switch seems to be working.

If the red-lights are from a CAN signal, does that mean that they are dictated by a sensor on the transmission for cable position?

EricJ., no I have not been under the car at all, and there is very little spring-tension at the end to hold the shifter in the final P position which is concerning but may be irrelevant.

The red-light could very well have burned out which makes assesment more difficult - but I'm not even sure that is the problem at all since the park-lock shift-alarm works perfectly and there is an audible (albeit quiet) click from the Park-position microswitch. The transmission is indeed shifting into Park, I've just tested this by stopping on an hill and moving into park (the car stays "parked" in place, does not roll and you can feel the transmission engage the gear-stop within about 1-2 inches of roll as the brake pedal is released.)

 

Maybe see if you can get hold of a replacement J gate panel, many people sell them separately to the J Gate mechanism. Have you tried to adjust the cable as per the instructions I sent you?

 

Stu, yes definitely, your instructions for adjustment were spot-on and now the shifter functions (besides P) work perfectly. Unfortunately at some point in the repair I gave myself a new problem that is questionably more-problematic.

Before buying parts, I need to determine which of the 3 possible issues are causing the car not to start and throwing the dash "engine fault" message:
- Jgate defective - would this issue happen if the J-gate electronics or mechanics were not operating right?

- if the shift linkage-cable was not engaging Park to its fully-seated notch on the transmission - what would happen? Maybe the cable is the issue?

- something electronic (harness/connector?) in the center dash is shorting from all the cleansors/grease I sprayed in there? Would that potentially cause this issue? If so, what connectors are "reporting" the car's gear position to be in P? Should I try disconnecting a bunch of cables in the center console and see if it starts with an open-circuit?

 

Should I try disconnecting a bunch of cables in the center console and see if it starts with an open-circuit? Is this a good idea and safe to do?

 

I am a strong believer that if a problem occurs after I "fixed" something, it is most likely related to whatever went through my hands during the process.
I don't think you should start to find the problem in non related connectors, but first concentrate on what you have done.

I read a rather long thread on this forum (either X308 or XK forum) where the connector to the small gear selector board (the one with the illumination on it) gave problems.
The guy went through everything, but finally found out the connector was the problem, re-soldered everything and problem solved.

Perhaps by taking everything apart, one of the connections broke?

 

I've read that same thread, lol - while that is possible, I never fully removed the JGate, just its screws and shifted it around to get underneath and was careful not to pull on it (since I too read that thread.) The connector would have to be excessively fragile to break under that.

I did not disconnect any electric harness, but I did get lubricant and grease all over most of the 5-6 of them down there.

 

Well, then I put my money on the cable adjustment, too tight or too loose, and no perfect synchronization between the J Gate setting and the gearbox setting.

In the documents Stu posted it is clearly mentioned to check the lever under the car (point 7 & 8), perhaps time to follow the complete instructions this time ?

Good luck.

 

Updates: a few days ago, without me doing anything, the car began starting in P, with the P indicator lighting up red for the first time in months (so the bulb is good!) and selecting the other gears perfectly. That lasted a few days while it was garaged, yesterday it was parked for a few hours in the 50 degree cold and wouldn't start in P again, screen showing "Failsafe engine mode" (my prior post stating engine fault was a mistake) but in neutral it started fine, and was VERY stiff to shift out of the park position (smooth once in/past R) and didn't engage the D indicator without shifting to 4 and back (old problem back).

All subsequent restarts and the shifting/starting worked perfectly, except the red P light worked only sometimes.

Apparently the cable is adjusted well (I think) but maybe temperature makes the cable length change? What would cause the stiffness between Park and reverse? What part can I swap (shifter cable?) to fix this without changing everything?