Push to start not working

[09A6]

2009 A6. Push to start isn't working. I installed a new battery in the key fob thinking that was the problem, it wasn't. Also noticed the fob won't lock/unlock the doors. I took the fob to the auto parts store to verify it was transmitting a signal on their RF tester and it was. Anyone run into this problem?

[Avantly]

The RF transmitter for lock/unlock and the proximity RF for push to start are two separate circuits. Is the key in good condition? Has any water gotten into it? Any chance you have a VCDS scan of the J518 module available?

[G-Can]

let me join on the question, mine has been acting up as well latelly.

I will get random Key not found, or key is in the car, and I will press start button, yet nothing happens, and I will watch the key flashing in my hand, ca does nothing, then randomly just starts on its own.
Battery replaced and good, multiple times.

Also, often wont unlcok the car when put my hand un the handle. Regardless which door.

no codes.

[Avantly]

let me join on the question, mine has been acting up as well latelly.

I will get random Key not found, or key is in the car, and I will press start button, yet nothing happens, and I will watch the key flashing in my hand, ca does nothing, then randomly just starts on its own.
Battery replaced and good, multiple times.

Also, often wont unlcok the car when put my hand un the handle. Regardless which door.

no codes.

Is there any chance that water has ever gotten in the key, or the battery contacts have lost their tension or are showing mild oxidation?


The prox circuit uses more current (very short bursts) than the typical wireless circuit for the remote lock/unlock. If you have any resistance in the power path the voltage may be collapsing too far during signalling causing a signal to noise ratio issue or outright failure to finish transmitting each burst.

The contact for the side of the battery also has spring tabs on the bottom of it which touch the circuit board and I've seen some of these circuit board pads look pretty bad on older keys. Before deciding it's not the fob I'd be tempted to disassemble the whole key (need two different sizes of teeny tiny torx bits) to clean it all up and check for any corrosion or other damage.