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Over the last week or so, I've been experiencing an intermittant error code. My OBDII reader gave me 2 error codes: P0706 & P0706 P.
I cancelled both error codes and since then, it has only come up with the same error message one more time.
By delving into the massive amount of information available on the WWW, I came across a Jaguar flowchart regarding this actual error, so I know that it could be one of 4 things:
1) The micro switches inside the J gate (I've checked both of them using a multi meter and they both "make and break" correctly).
2) The rotary switch attached to the gearbox.
3) the rotary switch connector block on the engine side of the bulkhead.
4) the TCM.
The only other clue, other than the error message shown when it does fail, is the red LED for the 'R' on the J gate doesn't illuminate, whereas all the other letters and numbers do?
When it does fail, the car goes into "limp home mode"' pulling away in 4th gear and the engine running on "restricted performance".
Any ideas anybody, or has anybody suffered the same problem and knows exactly what to do and how to sort it?
Many thanks
Last edited by Tony S; 07-12-2011 at 09:34 PM.
Reason: Spelling error ..... Doh!!
This is also happening to my car and this is what I have found out so far.
Transmission Fault Code P0706
Just thought I would share some information.
After my recent report on servicing my 97 XK8 transmission (fluid & filter) at 103,000 miles last month, the ungratefull car decided that it would break down on me. The symptoms were sort of similar to previous posts reported in 2004 but not quite the same as the ones I had.
The car would not change out of 1st gear and then once the revs were up to around 4,000 would not drive at all until it slowed but with no indication of a fault on the dashboard. If the J gate was moved into 3 then the transmission would lurch and the "Gearbox Fault" light would come on and the car was then in "limp home" mode, that is stuck in 4th or 5th gear but with no other indication but at least it was driveable, although VERY tricky to drive away from junctions with next to no power! The "Gearbox Fault" could be cleared by switching the car off and the fault would revert to the stuck in 1st gear one - until moving the J gate to 3. My cheap OBD2 fault code reader did not show any faults so I went to a recommended garage, and for the price of a drink I saw the offending fault code P0706 with no other codes showing. This code looks up as "Rotary Switch and/or D-4 switch malfunction". I elected to dismantle the J Gate assembly first and check all the switches and spray with switch cleaner, also to adjust the bowden cable. At this stage I noticed that the J gate indicator lights only indicated P, R, N but not D or 4,3,2 and on moving to 3 the gearbox fault light came on. I checked out the rotary switch from the ECU connector and found that the L3 switch was not operating. Removing the rotary switch from the side of the gearbox was very simple as it is only held by two 10mm headed screws, the connector which is located behind the engine at the top of the gearbox was the most tricky thing to uncouple. I had panicked before I diagnosed the switch and bought a low mileage gearbox on ebay so I was able to fit the switch pack from this and now the car drives perfectly again.
I narrowed down exactly what had to happen for the error to occur: all I had to do was shift from D to 4 until I was on 4 and D stayed lit, then shift up to 3, and boom, transmission fault.
I went to Advance Auto and reproduced the error, and had them read the code - P0706. I learned from the JTIS CD that there is no mechanical indication made on the tranny (i.e. the cable doesn't move) when the shifter goes from D to 4 and back - it just trips the D to 4 switch in the shifter module. But then when I shifted up to 3, the tranny detected that I was in third but the D to 4 switch was still open, so it knew something was wrong and switched to failsafe mode.
I figured then that my problem was actually in the D to 4 switch not working, not the rotary switch. I pulled apart the J-gate and after some fiddling determined that my switch was sound, but it was hanging down a bit low, so sometimes when the selector disc spun around, the tab that is supposed to depress the switch was above the roller on the switch, so it never was tripped. All I had to do was firmly seat the D to 4 switch so that it sat a little higher and stayed in the plane of the depressor tab on the selector disc.
Over the last week or so, I've been experiencing an intermittant error code. My OBDII reader gave me 2 error codes: P0706 & P0706 P.
I cancelled both error codes and since then, it has only come up with the same error message one more time.
By delving into the massive amount of information available on the WWW, I came across a Jaguar flowchart regarding this actual error, so I know that it could be one of 4 things:
1) The micro switches inside the J gate (I've checked both of them using a multi meter and thet both "make and break" correctly).
2) The rotary switch attached to the gearbox.
3) the rotary switch connector block on the engine side of the bulkhead.
4) the TCM.
The only other clue, other than the error message shown when it does fail, is the red LED for the 'R' on the J gate doesn't illuminate, whereas all the other letters and numbers do?
When it does fail, the car goes into "limp home mode"' pulling away in 4th gear and the engine running on "restricted performance".
Any ideas anybody, or has anybody suffered the same problem and knows exactly what to do and how to sort it?
Many thanks
Your description is classic for a failed Rotary Switch. Kudos for noticing the "R" going out. That's the giveaway, most people never notice that kind of stuff and makes our job a little harder.
Gareth, if you have any pictures to accompany your very nice writeup, that post would be a golden FAQ addition...most owners are a little wary to go the extent that you did, and its becoming a more common fault for these aging transmissions.
I will be doing my Daimler hopefully this weekend and it should be the same process on all X308 (XJ) models and the XK range so will take pictures to try to help with the repair process.
Your description is classic for a failed Rotary Switch. Kudos for noticing the "R" going out. That's the giveaway, most people never notice that kind of stuff and makes our job a little harder.
Cheers,
Thanks xjrguy, that's just the confirmation I needed.
Although I have to say, for the last 4-5 weeks the little bu**er has been behaving correctly, so I haven't been too concerned.
I had been waiting to use a friends 2 post ramp and also borrow the front ABS sensor ring removal tool, so I can replace a front wheel bearing.
Finally this should be taking place on Friday, so whilst the car is up in the air, I'll also swap out the rotary switch for a known working one.
Regarding noticing that the "R" LED was not working, I had recently done a lot of work to the J gate, namely replacing the two bulbs on the PCB that illuminate the green line around the J, fitting an aluminium 2 switch J Gate surround and fitting a cruise control switch because I've just retro fitted cruise control to my car. With that much attention being paid to the J Gate, noticing the lack of "R" LED sort of wasn't that difficult, especially with the ongoing at that time, P0706 error code.
Let's see what sort of problems I can stir up on Friday by replacing the rotary switch.
All the best
Last edited by Tony S; 07-12-2011 at 09:33 PM.
Reason: Bad grammar ....... Again Doh!
Your description is classic for a failed Rotary Switch. Kudos for noticing the "R" going out. That's the giveaway, most people never notice that kind of stuff and makes our job a little harder.
Cheers,
Just a stab in the dark here Steve, but you wouldn't by any chance have a Jaguar data sheet or the like on how to do a full function test on the gearbox rotary switch prior to fitting it.
The bloke I bought the rotary switch from assured me that it worked 100% with no known glitches or problems, but I'd rather perform a few checks of my own before fitting it.
Just a stab in the dark here Steve, but you wouldn't by any chance have a Jaguar data sheet or the like on how to do a full function test on the gearbox rotary switch prior to fitting it.
The bloke I bought the rotary switch from assured me that it worked 100% with no known glitches or problems, but I'd rather perform a few checks of my own before fitting it.
Many thanks
Well, it's not as straight forward as you might think, but, yes you can do it. The switches, with the exception of the Park-Neutral sw., form a digital input to the TCM. A certain combination indicates this gear or that gear. Attached is what you need to know for testing the switch. A zero in the grid box means that switch should be closed in that position. Now the D-4 switch is a separate item attached to the J-Gate, it is not a part of the rotary switch.
Well, it's not as straight forward as you might think, but, yes you can do it. The switches, with the exception of the Park-Neutral sw., form a digital input to the TCM. A certain combination indicates this gear or that gear. Attached is what you need to know for testing the switch. A zero in the grid box means that switch should be closed in that position. Now the D-4 switch is a separate item attached to the J-Gate, it is not a part of the rotary switch.
Good luck!
Many thanks Steve.
I've already tested the electrical and mechanical function of the D-4 switch and it's fine.
Now it's playtime with the rotary switch.
Had my tranny rebuilt and now when I manually downshift and go back to "D" I get a "Gearbox Fault" It can happen even if the car is not running. also if I go from "P" to "R" the "R" light comes on but if I go from "D" to "R" the "R" light doesn't come on unless I go a bit past "R". It will come on and allow me to put the J-gate lever back in "R".
The tranny guy says it is a bushing up-top around the shift lever area. I took off the trim and the J-gate and observed the lever in all it's gyrations. Didn't see much slop. I did however notice that the rearward micro switch looks like the metal lever that actuates the switch has broken off.
1) Did this switch ever have the metal arm like the front one?
1a) Could this being missing cause these symptoms?
2) Is it more likely that the shift linkage on the tranny is slightly maladjusted?
Didn't have the Gearbox fault until they worked on it and I don't remember the "R" light acting that way.
Switch in question.
Had my tranny rebuilt and now when I manually downshift and go back to "D" I get a "Gearbox Fault" It can happen even if the car is not running. also if I go from "P" to "R" the "R" light comes on but if I go from "D" to "R" the "R" light doesn't come on unless I go a bit past "R". It will come on and allow me to put the J-gate lever back in "R".
The tranny guy says it is a bushing up-top around the shift lever area. I took off the trim and the J-gate and observed the lever in all it's gyrations. Didn't see much slop. I did however notice that the rearward micro switch looks like the metal lever that actuates the switch has broken off.
1) Did this switch ever have the metal arm like the front one?
1a) Could this being missing cause these symptoms?
2) Is it more likely that the shift linkage on the tranny is slightly maladjusted?
Didn't have the Gearbox fault until they worked on it and I don't remember the "R" light acting that way. Switch in question.
Yep! That's a problem. That lever got knocked off most likely when someone was working on/adjusting the shifter. If you are lucky, some searching down below that switch may turn up the lever. If it's not damaged or bent up, it can probably be snapped back on.
Otherwise, you're gonna need that switch panel with both switches.
@AC0FC.
I have one of those on Ebay.
1998-2003 Jaguar 4940AD OEM Park/Neutral Safety Start Switch - 272503694278
Mine is a 1997, yours are '98 +. The metal actuator I see is the full length of the switch body (don't know about the missing one) so the acceptable length of activation would be different. Would this cause a problem? My rear switch is there, and works, but just in one small position of the gear lever.
Since I get the gearbox fault when moving the lever from the left side of the J-gate to the right, and I don't think the tranny guys messed with anything "top-side", I was more suspecting a minor misadjustment of the linkage going into the tranny. They WOULD have had to R&R that.
In the mean time, I'll look for the other lever. The mounting/pivot tabs are broken so I'll either need a new switch or I might be able to cobble something up to replace it.
I see where the side of your gear shift lever makes contact on the side of the little silver pivot lever (right where your arrow is pointing). Im sure that the whole bracket can be moved forward so that the shifter can make contact if need be, if you look at the ebay photo 4 you can see the oval mounting holes for that adjustment. You might have to re adjust the shift cable which is also attached to our bracket but its not a big deal, a turn or two of the nuts. Google search adjust shift cable for xj8.
Another option is to buy just the limit switch from radio shack, if not, a speciality electronics store, theres one here in SLC called RA-Elco Inc. 2780 Main St, South Salt Lake, UT 84115 (801)487-7749. You will have to drill out or sand grind the rivets off and place a small bolt and teflon nut to re attach, splice the old wiring harness to the new switch. MAKE SURE you get a OPEN type limit switch, this is one that the circuit is open when the lever/plunger switch is not depressed…. Ring out the two switches with a Ohm meter, if both are not depressed the upper one (park) will ring as a closed circuit, the lower one (neutral) will rings as a open circuit. In other words for the car to start both switches have to be open (pressing the park switch aka in park) or closed (pressing the neutral switch aka in neutral). Essentially they are like the two way light switches at the top and bottom of a stair well…. Both up; lights off, both down; lights off, one up one down; lights on.
Option three, if you can find the little lever part, drill a small hole thru the switch itself where the nip broke off and run a small both thru that with a teflon lock nut to re attach.
I dont think that this “broken” switch would cause a problem cause it just sits there in its natural open position all the time. However I could be wrong in the sense It might get triggered by the gear lever on its way down when shifting into drive telling some TCM or EM module that hey im on my way to drive but IDK. And you wouldent be able to start the car in neutral. I might have one of these switches from the soft top of a convertible SAAB i parted out, id have to look, but im sure it will be the closed curcuit kind. Ill let you know. Well best of luck I hope you get it sorted out.
I officially hate this piece of **** car. It all of a sudden went into limp mode as I was driving one day. Now when I put it in drive, the engine has to rev up to 3000 rpm before it does a hard shift into what seems to be 5th gear. I say this because it pulls off very slowly and it never shifts. Any suggestions before I start parting it out or find a Louisiana lake to bury it in?
Yes - start a thread of your own with some actual detail in, rather than spam multiple other threads with a general rant.
03-27-2011, 08:10 AM
Transmission fault code P0706
