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"GEARBOX FAULTY" : what does that mean?

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Wed Jun 05 2024, 04:13am
Joined: Apr 18 2024
Member No: #5495
Location: Los Angeles
After driving for 15 minutes, SERVICE notification light came on and "GEARBOX FAULTY".

I drove another 20 minutes / 20 miles after that notification appeared without a problem.

What does that "FAULTY GEARBOX" indicate on a C6? (2.7 HDI, 2006).

I parked the car for an hour and both the SERVICE Light and GEARBOX FAULTY disappeared when I restarted C6.

Then the SERVICE and Faulty Gearbox reappeared again after 10 minutes driving. I arrived home, and 10 minutes later restarted C6 and both SERVICE and GEARBOX FAULTY had gone away again.

Transmission works perfectly as far as I can tell.

This fault had appeared once before.

(and then I changed the transmission fluid 3 times for preventive maintenance).
Has another else had this mysterious "FAULTY GEARBOX" appear and then go away?
Mon Jun 10 2024, 07:04am
Joined: Sep 20 2016
Member No: #2793
Location: West Mids
One of the 'joys' of C6 ownership is the appearance of warnings which may or may not mean something. In the absence of a diagnostic kit, providing it is working OK and with no other signs of a problem, I would carry on motoring.

Did you have the transmission fluid changed by means of a pumped out change / replace, or simply by draining what will come out of its own accord ? In the latter case, you are only changing a minority percentage of the fluid. Either way, it might just be worth checking with the car level that the fluid content is correct.

As you have been using it, all the gearbox oilways will be full, so it's just a case of undoing the small centre plug within the drain plug and seeing what happens. If a quantity runs out, it has been too full; if nothing appears, you need to add fluid until it just starts to emerge from the plug.

If topping up, check that the correct fluid is used, as I think the fluid spec altered during the course of production. I'm sure there are threads tucked away on the forum about this. OK to use older spec fluid in a later box, but not the other way round, as I recall. (Do check - don't rely on my memory !).

As with all these things, it is worth as a matter of course checking for any furry connector blocks, or low battery voltage / poor battery.

Mon Jun 10 2024, 11:17am
Joined: Jun 09 2023
Member No: #5278
Location: Annaberg-Buchholz
Got also the "FAULTY GEARBOX" message once in past. However the gearbox is working well and I have driven 3000 km after that message without any issue.

Have done a preventive fully oil flushing of the gearbox - including cleaner - with the Liqui Moly system 4000 km before this message comes up.

I think it is a temporary interruption of synchronisation between engine and gearbox. No errors are visible related to the gearbox on Diagbox/Lexia.


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