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Thread: Gearbox fault light.

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    Member Pretator's Avatar
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    Gearbox fault light.

    Hi, I have been enjoying the good weather with trouble free motoring until today. After a 15 mile cruise down the A5 to a meeting, parked up forwards, reverse etc no problems. Car left for approx 45 minutes upon starting to leave engaged drive and gearbox fault light showed. Selected neutral switched off and re started after 10 seconds and all ok. Another 15 mile drive and then some stop and start trips no problems changes smooth, kick down, sports mode at redlines - perfect. Another 15 mile drive to pick up grandkids parked UPC for kfc. After about an hour started up engaged drive and fault re appeared. This time it didn't go off. Limped back to their place about 2 miles. Switched off and checked fuse, removed and replaced and fault light is off with normal driving re enabled. So has anyone got any ideas please?
    Am I looking for an electrical connection anomily. Gearbox oil and filter changed approximately 25 - 30000 miles ago. Also mechanically seems to function correctly. Also definitely not gearbox overheating fault light. Thanks in advance.
    1997 XK8 convertible, anthracite/cream. Normally aspirated 4l vvt. 100k chassis, 70k Jag replacement steel liner engine & zf 5 speed box. 18" alloys full spec optional extras. Refurbished rack,wheel bearings, brakes,front suspension+top arm polybush, IRS unit, ally thermostat upgrade, abs unit & associate electrics. Replaced head liner.

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    Senior Member DevonDavid's Avatar
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    I think this is one of those strange electrical faults that afflict our cars - particularly as they get older. My guess - and that's all it is at the moment - is that if you connected up a code reader, it might well show up a CAN fault - probably ECM to TCM or TCM to INST malfunction. Worth getting one if you haven't already - "Torque" for Android phone and a cheapo Bluetooth adapter can be had for a total of around £10.00 !!

    One fairly easy thing to check is the microswitches in the J Gate. I had a similar issue except I got lots of other warnings and lights as well. I unplugged, cleaned and reconnected all the connectors on the CAN circuit and, because the little metal tabs had broken off - I replaced the microswitch "unit" in the J Gate - picture shows the new one with metal "levers" intact. That was six months ago, and all has been good since then.

    The other question always to be asked with this sort of problem .................... are you 100% sure the battery is good. It may crank the engine OK bit if the volts fall below a critical level, it will throw up all sorts of strange issues.


    David.
    XK8 Convertible 4.0 - 1997. Aerial switch, boot lid switch, remote key-fob operated hood, & tensioners replaced.

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    Member Pretator's Avatar
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    David thanks for your input, the battery is definitely ok 12.78 volts measured today. It's a Bosch unit and I keep t trickle charger if I don't use the car for more than a week. That's not likely with this weather. I have to agree with your conclusion in this case as I removed and cleaned the gearbox plug and refitted with some vasaline and a rubber boot which I fashioned from an old headlamp bulb cover for protection. Also waggled the connectors to the module box bolted on top of the gearbox. Been for lots of drives today long short slow fast manuvers etc and it's not re appeared. If it does I'll check out these j gate switches you pointed out. One question concerning the j gate - is it meant to be illuminated when lights are on, apart from the red indication of drive mode?
    Also I note our cars are similar beasts.
    Thanks again.
    1997 XK8 convertible, anthracite/cream. Normally aspirated 4l vvt. 100k chassis, 70k Jag replacement steel liner engine & zf 5 speed box. 18" alloys full spec optional extras. Refurbished rack,wheel bearings, brakes,front suspension+top arm polybush, IRS unit, ally thermostat upgrade, abs unit & associate electrics. Replaced head liner.

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    Senior Member DevonDavid's Avatar
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    Yes - it is illuminated but ... the bulbs are soldered on to a small printed circuit board. Not difficult to do, but good eyesight and a very small soldering iron are essential. From memory, I think there are two bulbs - maybe three (?) - I got mine from RadioSpares I think. Can dig out the correct part number if you decide to do the job.

    Edit - I got mine here I think :

    http://cpc.farnell.com/sli-ebt/526-9...-0v/dp/LP00859

    but only one in stock at the moment. Plenty from RadioShack in the US - 272-1154 12v 50mA Bi-Pin bulb but ........ higher postage costs from US.
    Last edited by DevonDavid; 18-06-17 at 09:28.
    David.
    XK8 Convertible 4.0 - 1997. Aerial switch, boot lid switch, remote key-fob operated hood, & tensioners replaced.

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    Senior Member astromorg's Avatar
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    RS Components (That's UK, not to be confused with Radio Shack US) offer them in packs of 5 for £1.92 + VAT, free delivery. RS Part No 655-9491. 875 in stock!!
    2005 XK8 4.2-S Coupe and 2005 Auto SE 2.5 X Type Saloon

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    Thanks guys l will be doing this job and at the same time replacing the micro switches. Unfortunately after a great drive this morning, I went out this evening to the local shop (only 25 miles - honestly​ ) and it reared its gearbox fault. A quick remove and refit of the fuse and it's all ok. I did notice when the fault was illuminated there was a jolt selecting reverse and slippage moving forward. Once removing the fuse and reciting it functions normally. Could it be solenoids?. I'll​ replace the micro switches​ first and I guess it's the code reader if no joy. Could it be oil level ? Sorry to keep requesting help but while I'm ok with all the mechanical work and assembly of circuits and wiring etc the actual function of the circuitry is black magic to me. How does this code reader ap work?
    Thanks again.
    1997 XK8 convertible, anthracite/cream. Normally aspirated 4l vvt. 100k chassis, 70k Jag replacement steel liner engine & zf 5 speed box. 18" alloys full spec optional extras. Refurbished rack,wheel bearings, brakes,front suspension+top arm polybush, IRS unit, ally thermostat upgrade, abs unit & associate electrics. Replaced head liner.

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    Senior Member DevonDavid's Avatar
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    Others will probably give a better and more comprehensive summary but ............. pretty much all cars made during the past 25 years or so have the "ability" to be connected to a computer for fault diagnosis. There are manufacturer specific diagnostics machines which are very expensive, but very sophisticated, and allow the operator to interrogate, test, and in certain cases, re-programme all the various electronic modules in the vehicle. The Jaguar specific kit is WDS/SDD (Worldwide Diagnostics System / Symptom Driven Diagnosis ??) and is available in various hardware and software configurations from around £75.00 or so upwards.

    But - all manufacturers are obliged to provide a basic level of fault diagnosis called OBD (on board diagnosis) relating primarily to stuff which affects emissions but does include some other stuff. This is basically so that non-dealership type garages can diagnose and fix many faults on many different cars without the necessity for lots of different bits of kit. All cars have a DLC (Data Link Connector) somewhere near the driver's seat into which a diagnostics cable can be connected. In the XK8/XKR it is down in the plastic moulding by the driver's right knee. You have two options - a laptop with a wire connector to the car or, and much more convenient and easier, a Bluetooth adapter which plugs into the car, and an app for your PC or Phone to read the data. Many of us use "Torque" which is brilliant for Android phones - won't work on iPhones.
    This will allow you to read and erase "generic" codes, see live data (like engine temperature, fuel trims, engine revs etc., and also - in connection with the GPS function, show you how fast you were going, and where you were doing it !
    "Torque" is either free (with ads I think) or £2.95, and the adapters are available from China for les than £10.00. Just look on Ebay.I had problems with a very cheap adapter, and eventually spent a bit more on a PLX Adapter but others have had no problems with the basic kit.

    That's a very brief and superficial summary, but the ability to read the basic fault codes is essential for any diagnostics work on these cars, and a garage or dealer will charge a minimum of around £35.00 or so to give you that service.
    David.
    XK8 Convertible 4.0 - 1997. Aerial switch, boot lid switch, remote key-fob operated hood, & tensioners replaced.

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    David thanks for a comprehensive reply. I will instigate this as I am sure it will be a valuable asset for this car. In the meantime I was offered a code read from my friendly transmission expert who knows the cat from mot and other work in the past. He assures me it's not a mechanical fault due to its normal operation. He believes it to be the selector switch as they tend to wear and at 20 years old likely to be dirty inside a minute signal blip and up pops a fault. Anyway we will find out Friday. Also the lights arrived so something to do over the weekend.
    Again many thanks.
    1997 XK8 convertible, anthracite/cream. Normally aspirated 4l vvt. 100k chassis, 70k Jag replacement steel liner engine & zf 5 speed box. 18" alloys full spec optional extras. Refurbished rack,wheel bearings, brakes,front suspension+top arm polybush, IRS unit, ally thermostat upgrade, abs unit & associate electrics. Replaced head liner.

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    David apologies I didn't get back to you on the gearbox fault light. First up a garage mate put his code reader on it, it was the selector switch with a fault so easily fixed - thank you. Second I replaced the j gate illumination bulbs looks much better so thanks for info.
    Third I'll set up the blue tooth ap and reader as it's obvious it's invaluable to collect data. I read in a more recent post from you that you added headlamp vent. Did you purchase a kit or make them?
    1997 XK8 convertible, anthracite/cream. Normally aspirated 4l vvt. 100k chassis, 70k Jag replacement steel liner engine & zf 5 speed box. 18" alloys full spec optional extras. Refurbished rack,wheel bearings, brakes,front suspension+top arm polybush, IRS unit, ally thermostat upgrade, abs unit & associate electrics. Replaced head liner.

  11. #10
    Senior Member DevonDavid's Avatar
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    Not sure what thread that would have been. I used to get condensation in the headlight but cured it by cutting a small hole in the transparent removable section and using silicone sealant to hold one of these in place. Would post a photograph but as we all know, Photobucket has chucked it's toys out of the pram and I refuse to pay silly money when I only use it to post photographs on forums (fora ?) to help other people if I can.

    https://www.easy-irrigation.co.uk/wa...ppi4u53q3bgil4

    Got them for a local plumbing shop - cheap and easy fix. Had to buy a small hole saw the correct size, but that was only £1.00 or so.
    David.
    XK8 Convertible 4.0 - 1997. Aerial switch, boot lid switch, remote key-fob operated hood, & tensioners replaced.

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