TXcajunman

98 A8q

17606(P1198)-Oxygen (Lambda) Sensor Heater Circuit: B1 S2: Electrical Malfunction
17607(P1199)-Oxygen (Lambda) Sensor Heater Circuit: B2 S2: Electrical Malfunction
i am having some prbs added with 16538--b2 s1 o2 sensor no activity
where do i start to look at the wiring? i looked under the passenger floor mat looked clean no water damage didn't see any wiring thank you for any help

twentysevenlitres

You won't find the O2 sensors under the carpet...
The codes you have are mainly for the secondary O2 sensors behind the catalytic converters in the exhaust system.
They serve the purpose of monitoring catalytic converter function, and don't have much to do with how the engine runs.

That last code is for one of the primary O2 sensors (Bank 2 Sensor 1 which should be the right hand sensor (correct me if I'm wrong Sam!)).
You will find it under the bonnet behind the engine at the top of the right hand exhaust pipe. It can be accessed with the right tools.

The wiring for all the O2 sensors will be found on the firewall under the bonnet (hood) where the plugs are located. Left hand side ones are right next to the heater hoses. You'll find the right hand ones in a similar position on the right hand side.

You'll need to replace that Bank 2 Sensor 1 at least. They fail quite often and are generally past their best at 80-100,000 miles.

TXcajunman

i was going off a post to QW about some connectors that are underneath the floor mat. would both bank 1 o2 sensors malfunction cause stalling and takes about 5-10 to start after a stall? i am looking at replacing them both and hoping this would fix my newest prb thank you again for the help

twentysevenlitres

The primary (S1) O2 sensors are only used for fuel trim. Faulty or worn (S1) O2 sensors will give you high fuel consumption and maybe some knocking, but that's about it. They only work in closed loop, which is when the engine has warmed up.
The secondary (S2) sensors are only there to check the catalytic converter is doing its thing. They do not affect fuel trims.
Individually or together, they will not make your engine hard to start.

Hard start (lots of cranks, or two or more attempts) is most often caused by poor fuel pressure in the rail. This can be caused by a failing check valve on the fuel pump, failing fuel pump, a blocked fuel filter or fuel line, injector leak down, failing fuel pressure regulator.
In these cases, it is usually recommended to replace the fuel filter (you'll find it behind a plastic cover under the right hand rear door in front of the rear tyre). Most common fault on these cars once a few miles is up is a failing fuel pump. That's a job in itself but can be DIY'd. Mine had a similar issue and turned out to be a cracked hose on the fuel pump assembly.


If you're talking about the plugs under the carpet (under the MDF panel), that's the relay panel. Most relays are there including the fuel pump relay.