The gearbox fault code is displayed ,cold start heater lamp illuminates engine goes into limp mode. Switch off ignition and on again fault clears and car runs normally.
This fault happens intermittently usually when accelerating.
I would appreciate any help in tracing this fault

 

You need to get the codes read to pull up any errors; most garages have a code reader.

 

I had a similar situation recently - intermittent "Gearbox Fault" warning on my '03 gasoline engine X-Type. Code P1643.

Car went into limp mode, but after shut-down and re-start operated normally, until next gearbox fault.

Had the transmission fluid changed. All normal until "Gearbox Fault" recurred about a week later.

Searched this forum for "Gearbox Fault" and found other threads that suggested the Transmission Control Module (TCM) may have gone bad - or gotten wet. Jag wants $1,000 for a new TCM. Found a used one on Fleabay for $85. Taped it all up per the waterproof your TCM video posted here, and had it installed. That was over a month ago, and problem seems to be solved.

The new "Used" TCM I put in was from a car with over 120,000mi on it, and looked rougher than the one that was causing problems, but you can't argue with success.

Definitely get the codes read- but keep in mind those are often "indicators" of what the problem might be, and not necessarily an ironclad or definitive diagnosis.

 

So a new tcm ultimately fixed the gearbox fault code? How hard is that part to replace yourself ? I may need to look into that myself