Add me to this unwanted club. My '04 stype started showing "gearbox fault" this weekend. Like others, it got stuck in limp mode while in 3rd gear. Pulled over. Shut off the car then started her back up, the warning dissapeard, however at times she seems to shift a bit rough. Guess I'll start with the O2 sensor and pray for the best.

 

My XJ8L has gone into limp mode after a gear box code.

The trans does not engage unless you rev it to 2000 rpm & then with a thud it goes into 4th gear and runs in that gear only.

Reverse works fine though so I presume that it is not the trans but something electrical.

 

I have a 2000 XKR and the engine light came and went, then a few weeks ago came to stay. got a new gas cap (had evap code). Now of "Restricted Driving Mode" and just now "Gearbox Fault", but driving it seems normal. It does have an oil smell about it - had trqans leak fixed, waiting for oil to burn off, haven't driven in rain since.

?????

Rick

 

All the good old boy mechanics say the same about autobox faults. And that is "change the ATF fluid". My guess is that's likely to be a 60% chance of a fix, and shouldn't be horrendously expensive, and won't do any harm anyhow. My own son who is 'kinda' in the motor trade told me this without any prompting. I knew already, but kept my trap shut. Must be getting diplomatic in my old age...
Leedsman.

 

Wish a fluid change would do it, bad I had that done a couple of months ago. It seems like a whole host of problems cause these codes. What kind of engineering yields codes that can be so not so directly related to the message?

 

Well, on the other hand, I would like to hear someone honestly claim that they personally know of a modern, electronic controlled transmission that was not working and began working after an oil change.....

 

Rick, random errorcodes is a problem I'm not getting involved with again. As a technology, the microprocessor control of machinery is very different from straightforward mechanical engineering (partic. in the car environment) and seems to generate all sorts of fear, emotive reactions etc. among mechanics due to lack of proper training I suspect.
Unf. a quick scan on the interweb reveals that Jaguar are the most notorious maker for this random errorcode problem. It's got to the stage where huge amounts of money are being spent on changing major, expensive parts on just the say-so of the errorcode system, (check the BertrandGrey saga), when that same errorcode system itself is suspect. It's a problem I've seen and experienced often before with other micro-controlled machines. This very morning my adsl modem went mad and I fixed it by unplugging the power for a few seconds allowing a re-boot. Suffice it to say I fixed my own Jaguar restricted performance problem, and I posted the methodology here. I feel a bit like Pontius Pilate now, just drying off my hands...
Leedsman.
p.s If you read this BertrandGrey, I'm seeing the funny side too!

 

I got "Transmission Fault" with the yellow light, plus the Check Engine symbol lit up. On one ocasion, it went into Limp Home mode. Change from 2-3 is rough when hot. Can drives perfectly OK otherwise and no funny noises anywhere.

Well, last week the local main agents went through the diagnosis and the stored faults on my 2003 X350 and have told me it needs a revised program for the transmission control. It has to be done when car is cold so I have to leave car overnight. Transmission is the 6-speed ZF

 

there is another msg somewhere in the Jag For that tells where you can get just the part in question - don't remember just where...

 

Just yesterday, the 4th, I came off the hiway, top down, air on (oh, so green am I) near home and at a corner and I felt a big puff of hot engine air drift by and the RESTRICTED code came on - this happened the last time, too - thern upon rolling again the code went off; could this be a clue? "Le Chat Rouge" just farted and was all better?

Driving has not been restricted or altered with the coming and going of these codes. I will say the car would occasionally cut power on acceleration until I gat a new gas cap. So confusing! Jaguar desperately needs to issue an update of some sort achieved by some meaningful exchange between the programmers and the engineers, in order to sort this all out.

Rick

 

Rick, from what you say, I would check the engine coolant temperature sensor which is an NTC thermistor (NTC=negative temp. co-efficient). Use a common ohm-meter when engine is fully hot. I cant give you a figure for yours (you'll have to research it) but mine is 3K5 (3,500ohm) hot. NTC thermistors are known to collapse internally now and again, they break up into little cracked pieces.

Explanation: The coolant temp. sensor has a small current put through it by the micro. This results in a voltage across it, (usually in the 0 to 5v. region) which varies with coolant temp. The analog variable voltage is then a/d converted so the micro can use it. The look-up table has various strategies which are applied according to the indicated temperature. Eg., when engine is cold the A/F ratio is enrichened, the acceleration enrichment is increased. The strategies for petrol and diesel engines are different, diesel involving injection timing.

Testing the sensor is very simple and easy, anyone can do it. The cold resistance will be about 25 times the hot. Just tap the sensor gently while measuring to see if the reading jumps about. An analog meter is best, but digital will do.

Leedsman.

 

Check the wires at the connector for the throttle position sensor. It's completely unreasonable how the computer sends such catastrophic warnings to such a seemingly small issue, but it was 100% the problem. One wire was loose and soldering it solved the exact same symptoms that are being described here.

 

CousinDan has put his finger on the fault-finding/troubleshooting difference between analog and digital/microprocessor based equipment.
Because the control philosophy for microprocessor control is not like analog, "faults" can hide in the memory of the micro, showing up later as an inhibition of a control demand from the user. So it's quite possible the micro has 'noticed' an error from throttle position sensor, has obeyed its program instruction from the original programmer, and inhibited the execution of some later command from the user.
This is why "analog" thinking, so common among older engineers, will not work for troubleshooting microprocessor controllers. New and different thinking is required for both understanding and fixing just about all complex devices nowadays, simply because even your washing machine has a microprocessor.
"Built-in" troubleshooting as a feature of the micro's design and programming can itself be "faulty"! So even that can't always be trusted.
Leedsman.

 

I had the same fault on my 1997 XK8 (UK) last month; in my case there was a lot of moisture in the sealed box that holds the ECU and TCM.(under bonnet on passengers side next to the bulk head). I removed the 80way connector from the TCM and removed the unit, then dried the inside of the box. Reconnected the TCM and the transmission has been working fine.

 

Hi I have an 09 xf and the gearbox light came on while the vehicle was parked but it was on but no limp mode, not sure whats going on.

 

Jaguar XJ v8 drives good but stay in 4th gear or 3rd reverse is ok just when u put it in drive jerk off then it feels like it's in limp mode the gearbox fault comes up on dash

can eny 1 help plz

 

so when i hit 80 kms car goes to 40 kms and high RPM's Turn car off helps to reset. Seems like going to SPORT MODE helps, maybe. What about going to manual transmission? will that help ? any other useful tips?

i dont think there is any transmission fuel for the gearbox, correct?

thanks Sam

 

Answer: I have been experiencing the same problem, and like many said on this forum, I checked the air filter and found that it was very dirty; I then bought one and changed it, and the problem disappeared and it has been some many days now without experiencing that problem; and it is worth mentioning that it took me less than 5 minutes to replace the air filter.