RNS-D unlock code fault fix
Posted: Sat May 23, 2020 11:36 pm
This is a potential problem that involves the RNS-D head unit not accepting the correct anti theft unlock code and how it may be fixed.
I’ll start at the beginning. I had a known correct code for the above head unit however the unit would not accept this code.
If you’re suffering this issue then you’ve probably now locked your headunit, trying in vain to input what you know is the correct code. You’ll have found that your selector nob isn’t doing anything.
You need to leave you headunit on for an hour or so to resolve this issue.
One you’re able to play with your nob again don’t try to re-enter the code.
Now remove the head unit. You now need to test the voltage between the earth and the SAFE pin, you should be getting 12v however I was only getting 3v. You can also check the voltage at UB+ as this to should be getting 12v.
Now with a low voltage there you’ll have to find where the issue is.
After a lot of research I found that there was a connection under the passenger seat by the transmission tunnel. Knowing this and the fact that this area can get damp with scuttle drain hole issues I thought it best to check this area out. I moved the seat as far forward as I could, pulled the carpet by the tunnel and the seat runner out and took a picture of the cable run. As you can see there is copper oxidation, a sure sign that copper cable insulation has failed.
Unfortunately from this position I couldn’t really see what was going on let alone fix the problem so I set about removing the seat.
Remove both side end caps from the seat runners, they just popped off.
Then, with the electric seat adjuster, move the seat to near it’s furthest most position. Now remove the two 13mm bolts from the front of the seat under the plastic trim.
Unfortunately to be able to really get to the issue I had to cut the carpet a little from the front end of the seat runner cut toward the under seat vent. The cut is around 6” and is totally hidden when the seat is refitted.
Once you’ve gained access to work now would be the time to isolate the battery. Remove the black cable first, then the red, making sure that the battery won’t become live whilst you make the repair.
Now you’ll find that the all the red and orange strip cables are joined together in this one connector (there were seven lines in my connector). Gently twist the connector and the cable will come away.
Peel back some of the insulation and join the cables together. I used a wago block but use your preferred method.
Now reconnect the battery and check the voltage at the headunit connection block. You should now be getting 12v across the SAFE pin. You can now plug your RNS-D back in and enter your code.
If you have 12v reassemble your car. If not you can add to this post when you find you fault. 
I hope you’ve found this helpful. Thank you to other members on this forum who helped me piece together all the information that resulted in the solving of this issue.
I’ll start at the beginning. I had a known correct code for the above head unit however the unit would not accept this code.
If you’re suffering this issue then you’ve probably now locked your headunit, trying in vain to input what you know is the correct code. You’ll have found that your selector nob isn’t doing anything.
You need to leave you headunit on for an hour or so to resolve this issue.
After a lot of research I found that there was a connection under the passenger seat by the transmission tunnel. Knowing this and the fact that this area can get damp with scuttle drain hole issues I thought it best to check this area out. I moved the seat as far forward as I could, pulled the carpet by the tunnel and the seat runner out and took a picture of the cable run. As you can see there is copper oxidation, a sure sign that copper cable insulation has failed.
Remove both side end caps from the seat runners, they just popped off.
Now you’ll find that the all the red and orange strip cables are joined together in this one connector (there were seven lines in my connector). Gently twist the connector and the cable will come away.
Now reconnect the battery and check the voltage at the headunit connection block. You should now be getting 12v across the SAFE pin. You can now plug your RNS-D back in and enter your code.
I hope you’ve found this helpful. Thank you to other members on this forum who helped me piece together all the information that resulted in the solving of this issue.