I really like my '01 XJ8 but the transmission is driving me crazy (sometimes that seems like a very short ride!). A lot of the time the car drives fine. But the car goes into limp mode ("Restricted Performance") intermittently. I replaced the Rotary Switch and both Speed Sensors. I also replaced all the Microswitches under the J-Gate. None of those 6 things helped. I can clear the Limp Mode by turning the car off for 30 seconds and then it will be fine for a period of time. But then the fault will happen again, sooner or later. Sometimes it happens when I'm stopped at a red light. Sometimes it will happen when I am cruising along at a constant speed. Sometimes it will happen when I'm accelerating. I don't think it's ever happened when I've been braking.

As a test, I can usually purposely make it go into Limp Mode by manually shifting from D to 4, and sometimes from 4 to 3 or 3 to 2. If it doesn't make it go into Limp Mode by going from D to 4 (let's say there's an 85% chance it will do that) it will more likely than the 85% (let's say 95%) make it go into Limp from 4 to 3. But in the 5% that it doesn't go into Limp Mode by going from 4 to 3 then 100% of the time I can go from 3 to 2 (or anywhere else on the shift gate) without going into Limp Mode. There's only a 5% chance that I will immediately get a Transmission Fault by going from Park to D...usually only happens when I am in motion (or as below, by manually shifting the gearshift, while either in motion or parked). Whether the Transmission Fault will happen 1 minute after starting to drive or 1 hour after a drive begins seems totally random.

I will give you more information I think is related: The gear indicator (P-R-N-D-4-3-2) normally illuminates the gear selection you have made (i.e., whether Park, Neutral, Drive, etc.) when the ignition is on, right? Right. I notice that sometimes there is a delay of between ~0.25-2.0 seconds before the D lights up after physically moving the gear shift into D, even though I pretty much immediately feel the car engage in gear...still the illumination of the D is delayed). Sometimes the P-R-N-D-4-3-2 doesn't illuminate any selection at all (any selection of gear) and then in that situation I will definitely I'll get a Transmission Fault and it will immediately give me a Transmission Fault text message.

Sometimes if I put it in Drive and the D doesn't illuminate immediately I can give it a little bit of gas (just a little) to get the light to light up -- I have no idea whether the following is factual but it's almost like I'm pumping transmission fluid around by revving it and that's helping it. Bad transmission valve? It "feels" like a bad sensor from the way it's behaving. The transmission seems to shift gears perfectly when it's not in Limp Mode. Doesn't leak anything, doesn't make any noises, etc. How could that be a bad valve or other mechanical part? Has to be a sensor, right? If I had a reset button on the dashboard that reset everything instantly like turning off the car for 30 seconds accomplishes, that would be great! Of course that's not possible but I'm just imagining that it would achieve me being able to use the car again.

Some more characteristics: Sometimes the car will start from sitting overnight and immediately show a Transmission Fault. I have regularly changed the fluid with correct Esso ATF LT 71141 fluid and filter. It's all new fluid.

The OBDII still indicates various codes right now:

Pending Code P706 - The book says that means, "Rotary Switch And/Or D-4 Switch Malfunction" but the OBDII Reader itself displays that P706 means "Transmission Range Sensor A Circuit"

A technician at the dealer said to hard reset the computer by disconnecting the battery cables and then touching the terminal ends together. I tried that. Didn't help.

The dealer is saying they want $160+tax for a diagnosis and only their $100,000 diagnostic computer can be specific about what is wrong and is no comparison for an OBDII reading (even though they probably connect their computer to the same Onboard Diagnostic port as my Harbor Freight OBDII reader). That seems like Highway Robbery and also not likely to be factual -- really, only their computer can read my car's systems properly? What about all the indy Jag shops? How do they do it? Maybe they just replace every single sensor one by one (or all at once) until they find the faulty one.

Can anyone please help figure out this transmission fault?? I would be supremely appreciative if anyone can help at all.

Crank
2001 Jaguar XJ8 105,000 miles
1955 MG TF Supercharged (Unknown miles)

 

Many indy shops can read transmission, abs and body codes. But they often want close to $100. I think you need to spend some money to get at this problem.

 

Just noticed you are in Georgia. If not too far from me, bring it over. I have Autoenginuity software and can read the codes. Glad to help. Send PM to make arrangements.

 

I am not near Douglasville, otherwise I'd take you up on that. I Googled Autoenginuity to see what it is and how it relates to Jaguar in my never ending quest to find out about the mysterious "Jaguar Dealer only $100,000 diagnostic computer," they want to charge me $160+tax to get a reading from, thinking maybe an Autoenginuity device is really what they are using with a Jaguar cat logo sticker on it over where it otherwise says "Autoenginuity." I understand the Autoenginuity device outputs live data for the user (which I wouldn't be able to read on my own, unless it were something really obvious...I recall seeing a -40 degree celcius reading on a Ford Truck which although the OBD reader said some overly general fuel system fault it was actually a bad coolant temp sensor...obviously can't run at -40). And then Autoenginuity can read various unique Jaguar modules (as you say, ABS, Transmission, airbag, etc.) and can reset sensors and modules and do cross tests and simulate their live use. Is that really all they use and do at the dealer with the mysterious "diagnostic" computer?

 

This is a picture of the OBDII fault code....what does the "$11" mean in the superscript to the right of the code? Do they want to charge $11 to get more specific about what the code means?

 

If you download the Jag manual JTIS21 from the sticky on the forum page you can look up the fault codes yourself and take it from there. P0706 may relate to switch D-4 or the rotary switch, but you need to select the codes related to your VIN to be sure.
The Jaguar dealer is not using Autoenginuity. They are able to tie into the factory via the internet and also address individual modules and run a refresh, etc.
I am headed to a local electronic specialist this morning to see if he can diagnose the cruise control problem I have with my XK8. Autoengiuity is not able to help.

 

Here is the PDF file - DTC fault codes for your 2001 XJ8 transmisson (5HP24):

5HP2400.PDF

Page 4 has the P0706 DTC information.

FAULT DESCRIPTION
Rotary switch and/or D – 4 switch malfunction

POSSIBLE CAUSES
Selector cable adjustment / installation incorrect
D – 4 switch dislocated
D – 4 switch to TCM circuit open circuit or short circuit to ground
D – 4 switch failure
Rotary switch to TCM circuit open circuit or short circuit to ground
Rotary switch failure


I copied the following detailed information from a Jaguar Service Training document (PDF file) on Jaguar Transmission (TCM inputs - 5HP24) that I found on forum member Gus website (jagrepair):

D–4 Switch
The normally open (Drive range) D – 4 switch, located at the J-gate selector, provides the TCM with an voltage input when the gear selector is moved from one side to the other.
This input is required as no selector cable and range sensor movement occurs during the side-ways movement.

Transmission Rotary Switch
The digital rotary switch is mounted on the right hand side of the transmission and is operated by transmission gear selector shaft.

Selection of a particular gear generates a 4-bit binary coded signal which is transmitted directly to the TCM over a four wire parallel interface. The rotary switch bolts directly to the transmission case and does not require a service tool for installation.

In addition to the gear selector positions, the rotary switch incorporates a separate Park/Neutral open/close switch used for engine start inhibit.

NOTE: If the selector cable is incorrectly adjusted, the range selector may transmit an invalid code, which would cause a DTC to be flagged.

Images of the 2 switches:



Here is the PDF file:

Rotary%20Switch%205HP24.pdf

Jim Lombardi

 

Also found in JTIS external controls for transmission -

Symptom Chart
DTC P0706 Transmission range sensor circuit range / performance

Possible Source(s)
Selector cable maladjusted
Rotary switch fault
D to 4 switch fault
Rotary position switch fault
Harness fault
Connector pins(s) bent, loose or corroded

Jim Lombardi

 

Does this mean there are two switches with the word "rotary" in them? 1) Rotary Switch, 2) Rotary Position Switch ?

Also, I don't seem to have a D-4 switch where the arrow points on the diagram posted (diagram T20 1/3.14). It just looks empty there. It's always worked fine without one there. Is that strange? It must exist in some other location...

 

You are not alone in this situation, I'm having this kind of trouble with my 2003 xj8 also.

 

If the selector cable is incorrectly adjusted, the range selector may transmit
an invalid code, which would cause a DTC to be flagged.