RDU repair leads to 4WD Fault message

[Caro]

My 2021 Outer Banks was shuttering when turning at slow speeds. I took it to the dealer for repair and they determined the RDU needed to be replaced in addition to the PTU. After the repair alerts were showing up on the screen so they recommended the AWD control was needed. The AWD control is not covered under the powertrain warranty so had to pay for that repair. After the new control was put in the dashboard messages continued. They then said the RDU actuator motor had an internal fault on the new RDU and that needed replacement. The tech notes say he cleared the codes and road tested and messages are no longer on the screen. I was called and told the car is ready.

I went to the dealer, paid for the AWD control module and was happy to have my car back after 2.5 weeks. After pressing the power button, 4WD Fault Service Required, See Manual, Park Aid Fault flashed on the screen. Prior to taking it in for the RDU repair there was never a message on the screen. They are now re diagnosing the issue and think it is a wire harness. Part alone is over $1000. Per the dealer, labor they won't be able to tell me for a few days because the whole car has to be taken apart and need time to figure it out.

Has anyone had a similar issue happen to their BS or know what could be wrong? Suggestions I could have the dealer check? It's been there three weeks and I am unsure if they know what really is the issue. I appreciate any recommendations you all might have.

Edit to add the mileage is 56K so under the powertrain warranty. The RDU & PTU were covered

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[Dude]

Sounds very much like the dealership service department caused more issues than they fixed but now are putting you on the hook to cover their mistakes

very sorry to hear that

and to answer your question, a number of owners reported their RDU needed to be repaired/replaced and most were under warranty

there are also a handful of posts regarding the AWD control module needing replacement but virtually all of those are unrelated to the RDU failure - it really sounds like based on the info you provided the AWD control module likely was replaced unnecessarily but only the tech knows for sure and even then the tech may not have realized the module was good

 

[Dude]

And there are various reports of rodents chewing up wires - but I’d have the dealership show you the bad wire harness while it’s still on the vehicle before they remove a wire harness (assuming that becomes their proposed repair)

 

[Uncle Brad]

Did you change a tire recently? Do you have dissimilar tire vendors or sizes? These are AWD systems (not a true 4WD with mechanical diffs and a transfer case) and some can even be sensitive to varying tread depths. The sensors and firmware are constantly evaluating the attributes of all four wheels and trying to accommodate accordingly.

 

[Caro]

Did you change a tire recently? Do you have dissimilar tire vendors or sizes? These are AWD systems (not a true 4WD with mechanical diffs and a transfer case) and some can even be sensitive to varying tread depths. The sensors and firmware are constantly evaluating the attributes of all four wheels and trying to accommodate accordingly.

Thanks for the idea. All four tires were new in March of this year. They are the same brand & size.

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