I have and 01 a6 with the 2.7 t was looking for some help and advice. Has the common issue upon lite acceleration i get the abs and esp light coming on at the same time for about 5-10 seconds than goes off. Brought to my mechanic just to have him narrow it down some heres what he gave me.

Code p1857

he said wrong ecu or wrong trans ecu or bad wiring between the main ecu and trans ecu

when i got the title from the dealership it said rebuilt from flood which i did not know when i bought.

I took a look at the ecu and tcm they seem to be original and the lights dont always come on just some times and it seems like more of and intermitt problem leaning me towards the wiring obviously.

Was wondering where to start or what to check for from here. I dont plan on bringing it to the audi dealer to get raped. Thanks in advance

 

I would start by cleaning the Mass Air Flow sensor.

 

check the brake lights. I had that same on and all my brake lights are not working. Others said their brake lights all ON without pressing the brake pedal. It is due to bad brake pedal light switch. A cheap fix $12.00
Yours may be just started and the switch is not completely failed.