B8 A4 BCM2 Swap - Tech Experiencing Issues

[DanielHamilton]

So I'm attempting to retrofit a "highline" BCM2 (J393) to my '11 A4 Avant P+ so that I can get things like side assist and power tailgate working. Recall that the 05 Acc/Start (immobilizer) lives on the same physical circuit board as the BCM2, so swapping that requires swapping the immo.

Original BCM2 was 8K0907064CF. Replacement is 8K0907064CS with the extra connections for the blue T32e connector. Both are 315 Mhz.

I installed the new -CS module and it communicates with the CAN controller fine; I was able to do the VCDS coding and even talk to the J605 (tailgate motor) I had retrofitted (and which plugs into the J393).

However, the -CS obviously won't start the car because it has CP/immobilizer active. So I took it to a shop with ODIS Online who assured me they did immo swaps and could do it.

After two days, the tech has given up, saying he's completely unable to get the 05 Acc/Start immobilizer to "stay awake" and talk to his programmer. It's working and getting power, it just doesn't recognize the key, so it goes to sleep a few seconds after inserting the key. He's telling me the problem is probably that my key is not an "advanced key" and that he'll try it again if I can source a blank advanced key.

From what I understand, the key itself isn't advanced or not - the part number is the same. It's just a question of whether the highline BCM2 is installed and the keyless antennas and start/stop switch are installed. The plug in the dash to start the car the old-fashioned way is the same too. Is that not correct?

Assume I take this to the dealer - what do they do differently for a BCM2 swap that this tech appears not to understand?

[Smac770]

Can't be sure. When I needed to replace my J393 with a used replacement off eBay, I took it to the dealership and they swapped and programmed the new one for one hour labor. But I was replacing like with like (well, updated rev, but same function level, replaced AH with AN).

The key could be not RFID enabled if your original vehicle config was not Advanced Key. There are with and without RFID keys.

What's the specific p/n on the key? It needs to be a "TKE" to be RFID enabled. Do you have an 8T0 959 754 A, 8T0 959 754 G TKE, or 8K0 959 754 B TKE? These are the 5D2 (315MHz) not-S/RS marked fobs for B8. My MY09 Advanced Key keys are marked 8T0...G (TKE).

[DanielHamilton]

My key is an 8T0 959 754 A.

Doing more research and yeah there are two different circuit boards, one with a very obvious transceiver coil for keyless. Mine doesn't have that.

Putting the old key into the dash slot with the new BCM gave a "Please remove key." So in some sense the car knows the key exists, even with the new BCM2. Can keyless cars start non-keylessly with a non-keyless key? Isn't that why they retain the dash slot?

[Smac770]

RFID is not used in the dash slot. RFID is used for the keyless operations. The dash slot is probably better referred to as NFC.

As for the guy's issue trying to run the immobilizer adaptation, no idea what the issue is there. Not something I've done. But as for simply swapping the CF with CS, and cloning the old identity to the new J393, I would expect it should be easy enough. Afterwards, you can change up the coding in the J393 to flips bits and such. But the immobilizer and keys should already be good. But you won't be doing any keyless entry / keyless go with that key fob.

I'd start with the old module in the car, everything as it came from the factory. Then simply take the replacement unit to a dealership and ask them to replace the current J393 with the replacement J393, immobilizer master replacement. Should be a one hour bill. After that, you'll have the CS working exactly like the CF did. Then you can play with the long coding to mess with the tail gate motors.

No point bothering with the keyless stuff until you work out getting a new key. At which time, you'll need to do the immobilizer adaptation again to adapt the new key to the immobilizer.

But, from a thread on mhhauto, "During all programming stay pushing a lot of time on the break pedal and hazard light on!", to keep the car modules awake. Maybe that would be enough for the guy to work your car.