"RDS-TMC connection fault"

[rs4-sson]

Guys

Following annoying error message comes up within 5 seconds of turning on Sat Nav:

"RDS-TMC connection: RDS-TMC connection is faulty or could not be established"

The only way to clear (accept) the message is to press the right hand selection nob. This has been posted before but for that lucky chap, the issue righted itself. Mine has been going for a week now and wondering if a "hard reset" of the system is required or if I need to replace some element of the hardware (hope not to the latter).

Any ideas gents?

Cheers[/url]

[peterb]

Well, I guess it means that the Nav+ can't find the TMC unit, so either the CAN bus wires between Nav+ and TMC are broken, the TMC module itself is broken, or isn't receiving power (or the Nav+ has got confused).

Vag Com disgnostics should be able to provide a little more information - such as the health of the link between instrument cluster and TMC.

Are you still getting Navigation and/or Radio information displayed in the Instrument cluster?

I might be inclined to disconnect power from the Nav+ and TMC units to see whether a power cycle fixes it.

[rs4-sson]

Thanks for the suggestions peterb

I haven't got around to getting a VAG-COM yet so I'll just try and disconnect the power from the NAV+ units in the boot (and the reconnect)and hope that clears the error.

I'll post again with any results.

Thanks again

[shineydave]

the TMC unit on mine is to the left of the steering column, dead easy to get to, think it's just 5 8mm bolts holding the panel under the wheel on

[rs4-sson]

Update: Answering one of peterb's queries actually but it turns out (didn't notice before) that none of the info from radio, nav, CD player is being displayed in on the DIS. The top third of the middle column is where you see track info, radio station, nav directions etc but it's completely blank.

Error message still comes (twice). Once after the system starts and again about 3 seconds after you clear the first one! Then it doesn't come back again until you re-start the system.

Will take to Audi tomorrow so they can do some diags on it for good measure. Maybe that will shed some light.

Cheers

[peterb]

Update: Answering one of peterb's queries actually but it turns out (didn't notice before) that none of the info from radio, nav, CD player is being displayed in on the DIS. The top third of the middle column is where you see track info, radio station, nav directions etc but it's completely blank.

Okay - so the entire CAN bus communication between Nav+ and the rest of the car has gone awol.

Dumping fault codes should indicate whether there is communication between cluster and TMC module. If not, suspect dead TMC module, or lack of power to it. If the TMC module is still visible to the cluster, then there's some problem on the Bosch CAN bus side - could be wiring or a fault in either unit.

[MK4ASH]

This problem is really common, originally on the S8 but now the devil is spreading!!! Disconnect the battery and leave it for a couple of hours, ideally over night and the fault should clear.

Good luck

Ash

[Dippy]

Okay - so the entire CAN bus communication between Nav+ and the rest of the car has gone awol.

Might not be quite that bad. Not sure about the newer cars, but certainly on mine the TMC unit is actually a TMC/CAN gateway, so it enables the SatNav and radio to display on the DIS. Without it, the DIS goes blank as described.

So either your TMC/CANG has bust, or maybe a connector has come loose. Either way you'll need to check it (if you need a new one you'll need to check the revision code).

Depending on the car, you should be able to find it quite easily by taking off some trim. On the A4 chassis, you just have to lower the knee bolster (3 or 4 hexhead bolts) and it's there on a bracket just to the left at the front (if an OEM fit).

[rs4-sson]

Thanks guys for your replies.

The Audi tech only had 20 mins to look at the problem and sure enough, the Audi diagnostic machine found the fault. The only issue is that the fault report did not specify where the issue was.

I will try disconnecting the battery and then looking at the TMC/CAN gateway to see if there is a loose connection.

Does anybody know where in the RS4 this little doo-daa is (pics would be great) since I don't actually know what a "knee bolster" is.

In the event that I need a new TMC/CAN gateway, where would I find the revision code to which Dippy refers?

Cheers

[rs4-sson]

OK - found the knee bolster.

Unscrewed the two 8mm hex screws on the bottom. Removed the fuse cover on the left side of the dash to reveal 2 more 8mm screws. Unscrewed them and then the bolster just fell away.

The TMC/CAN gateway I think is a silver box with 2 metal connectors and one bigger, black plastic connector. None of them loose unfortunately, no tell tales of anything amiss at all. Replaced bolster and have disconnected the battery as per Ash's advice.

Will leave off for a couple of hours and then turn on NAV. Otherwise back to Audi on Friday for a full diagnosis of where the fault is. Already been warned that Nav system might need replacing (worst case). bl00dy hope not......

Anyway, thanks for the pearls gents and please all pray along with me that it isn't the Nav unit that's kaputt. Will of course let you know the verdict.

Cheers

[rs4-sson]

Update:

As per Ash's suggestion, disconnected the battery overnight and this seems to have fixed the problem. Certianly a cheaper solution than replacing the NAV+ system!

Thanks again for your help

[Dippy]

Good news. Yes that was the TMC box you described. In the event that the problem isn't permanently fixed, you'll find the part number on the side of the box itself. They are available on ebay.de

[MK4ASH]

Fingers crossed!!