New here and need help with codes.

[98Quattro]

Hi there. I'm a newb on this site and wanted to say hello.
I own a 98 A6 Quattro 2.8L.

I just replaced my pre-cat O2 sensors about a week ago and the check engine light came on. With my buddy's VAG-COM I received these codes:

Address 01: Engine Labels: 078-907-551-AHA.lbl
Part No: 4D0 907 551 AH
Component: 2.8L V6/5V MOTR AT D01
Coding: 06252
Shop #: WSC 23261
5 Faults Found:
16795 - Secondary Air Injection System: Incorrect Flow Detected
P0411 - 35-10 - - - Intermittent
16535 - Oxygen (Lambda) Sensor B2 S1: Signal too Low
P0151 - 35-00 - -
16515 - Oxygen (Lambda) Sensor B1 S1: Signal too Low
P0131 - 35-00 - -
17604 - Oxygen (Lambda) Sensor Heater Circuit: B1 S1: Electrical Malfunction
P1196 - 35-00 - -
17605 - Oxygen (Lambda) Sensor Heater Circuit: B2 S1: Electrical Malfunction
P1197 - 35-00 - -
Readiness: 0000 0000

And

Address 08: Auto HVAC Labels: 4B0-820-043-MY1.lbl
Part No: 4B0 820 043 G
Component: A6-Klimavollautomat D61
Coding: 00160
Shop #: WSC 42006
1 Fault Found:
01273 - Fresh Air Blower (V2)
17-10 - Control Difference - Intermittent

We reset the codes and last night the CEL came back on. I know my secondary air Injection pump is bad since last year but the CEL has always gone off. This one stays on.
What could it be? What is the fresh air blower?

Thanks in advance.
Al

 

[Flying Spanner]

Hi, you need to check the circuit for voltage supply to the O2 heater elements. As it shows bank 1 AND bank 2 sensor 1 (pre cat) start with the fuse and work down the wiring diag to earth.
Your secondary pump being faulty wont help the low flow. If its bad, it can blow the Ebox fuse. Also check the rubber vac hoses down the back of the heads going to the combi valves, they always perish on the early V6 engines and cause a fault log but it would say bank 1 or 2 (cyl 1-3 or 4-6).
The O2 sensors pick up when the secondary air is working so as they are showing signal too low you would be best trying to sort this issue first.
Why did you replace the sensors? was it due to these fault codes or did these codes appear after replacing the sensors?
Did you use genuine parts/second hand or pattern parts when they were replaced?