Intermittent Gearbox Fault

[ianfullick434]

My 1999 XK8 will not start (engine will crank over) occasionally after a short run with Gearbox Fault on the dash. I have changed the gear shifter complete with micro switches. Is there a relay which controls the gearbox and or ancillaries? Any help would be greatly appreciated.

[mike020150]

The car might have more than one fault so it's good practice to gather as much information as possible before diving in to replace components which might or might not be the guilty parties. If you haven't already done so, download any stored ECU codes using a code reader. They might give some extra clues. Since the gear selector has been changed, do the leds alongside each gear position light up when that gear is selected? If not, it's possible that the linear switch is out of adjustment. Mike.

[ianfullick434]

Hi Mike,

Thanks for the response, yes the LEDS do light up, it does only seem to have this problem when the car is hot (not sure if this has any bearing) when left for a while say half an hour it will start.
I have had a relay problem recently which begs me to ask the question is there a relay associated with the transmission? I am reluctant to use the car in its present state but will visit my local garage next week to get the fault code readings.

Thanks again

Ian

[Astromorg]

As an alternative to getting a garage to read the codes, why not equip yourself with the means to do it yourself? Perhaps the simplest and cheapest is to purchase one of these from Ebay
https://www.ebay.co.uk/itm/153070323028 ... %3A2334524
Then download the app Torquepro to your mobile phone from either the Apple Store or Google Play Store as appropriate to your phone for about a fiver. Plug the Viecar into the diagnostic socket in your car, turn on ignition and pair the reader to your phone. Then you can read the codes for engine and transmission and much more besides. It's easier to do than it is to explain it and it's probably cheaper than one set of readings from a garage!

[ianfullick434]

Thanks for that I will look into the reader, although my local mechanic doesn't charge me as i use the garage for both our cars.

[Andy P]

Why not equip yourself with the means to do it yourself? Perhaps the simplest and cheapest is to purchase one of these from Ebay
https://www.ebay.co.uk/itm/153070323028 ... %3A2334524

Totally agree with Astromorg,it is one of the best "tools" to have with these cars.
I have three altogether as I keep them plugged in all the time and check them regularly(about once a month).
You should have the P1111 code at all times which means all 'readiness' tests are completed.
If you clear a P1111 you will get a P1000. Then you drive until you get all 'readiness' tests are completed again and you get P1111 which in short means the car is happy.
Could not live without mine
Good luck on chasing down your gearbox fault.
Take care.
Andy

[ianfullick434]

Thought I had it fixed but alas no. Have had the gear shifter replaced with a 2nd hand one (the original Neutral micro switch was broken), but this afternoon having parked when I tried to restart the dash readout read Traction control Failure then Gearbox Fault then Engine Failsafe mode and engine would not start. The car did start in Neutral . When I reached home the car started with no problems several times and there were no faults on my cheap OBD reader. Does anyone have any suggestions?

[JimMann]

Hi Ian, I am afraid the obvious next question is what age and condition is the battery? On these cars it is advisable to change a battery at 5 years, as an aged battery can throw up any number of spurious fault lights, i.e. dash lights up but there is nothing actually wrong. If it is more than 5 years old, then I would definitely recommend a change to a proper battery fit for the car.
Jim

[ianfullick434]

Thanks Jim I will test battery again.

[ianfullick434]

Well, after much investigation my local garage seems to have cracked my intermittent gearbox fault at last. The only fault code related to the cars security system, and on investigation the associated relay was found to be very hot it was replaced and hey presto all seems well.
Thanks all for your responses.

[mike020150]

You can't beat seeing a car in the flesh when making a diagnosis! Mike.

[Astromorg]

That's really interesting (to me anyway!)

I don't think I hold any fault codes for the security system, so I'd certainly be grateful to know this one for possible future use. Similarly, can the offending relay be identified by any chance. I know garages can be a bit reluctant to give up this sort of info sometimes, but I thought it worth asking on the off-chance

[Andy P]

Hi Astromorg.
I have one code relating to the security system in DTC Summaries AJ27 Engine Management – 1999 MY which is as follows:
P1260 Security input malfunction.
Ignition ON > 10 seconds.
OBDll: N.
CK EGN: N.
OTHER: N
DEFAULT ACTION: None
POSSIBLE CAUSES: KTM to ECM circuit short circuit,high resistance or open circuit.
Loss of ignition switched power supply to the ECM PIN EM82-09 for greater than 16 milliseconds.
KTM failure.
Security system incorrectly configured (KTM / ECM).

If you haven't got the DTC Summaries AJ27 Engine Management – 1999 MY PDF
I can send it to you.
Take care.
Andy

[Astromorg]

Now you've given me the number Andy I have found it in my own list. My oversight. Thank you for taking the trouble; appreciated.

The odd thing about that code is that it doesn't have a dash warning light or message associated with it. Perhaps a positive ID of the overheating relay would give a lead as to what was causing Ian's problem?

[ianfullick434]

I will ask my garage next week.
Used the car yesterday still ok .