Need a new upstream o2 sensor for my 2001 A4 1.8t.

- There are several Bosch sensors that claim to be the correct one for my car, does anyone have a specific one to recommend?

- Since I'll need to splice the new sensor onto the current connector, does anyone have a pinout? I'd also like to put an AF ratio gauge on there while I'm at it. Am I correct that there should be two heater wires, two lambda current wires, and one signal wire?

Thanks!

 

My dear advice to you is to find the 02 Sensor dummies online and plug them up instead of removing your 02 Sensor. There are two reasons. I've replaced a couple 02 Sensors before on other cars (sisters, friends), but when I replaced my 02 Sensor, specifically the B1S2 (passenger side, rear sensor), I stripped the thread. Being that I had replaced the passenger side CAT a while ago, the 02 sensor was in a different position than the B2S2 02 Sensor which had the original CAT behind it. That's the reason I couldn't just use a tap and die to get a new thread. So I had to resort to cold weld and heat wrap with some clamps to hold the damned sensor in place.

Reason #2: The dummies are a lot cheaper. They go for like 50 bucks I hear. Bosch 02's go for like 120+. 70 bucks is 70 bucks.

 

For the 2001 model 1.8T, I found this on AutoHaus AZ's website:
Your Parts Search Returned 4 Part(s)
Also on ECS Tuning's site:
OEM / Performance Parts for Audi, BMW, Mercedes Benz, Mini, Porsche & Volkswagen - ECS Tuning

If you input the OEM part number 1K0998262D into Autohaus AZ search, you get the Bosch 17351. Notice it's $13 cheaper than ECS Tuning, plus free shipping.
And it's even cheaper on Amazon:

This Bosch O2 sensor has the correct plug already.

About tapping into the existing wideband O2 sensor:
air/fuel gauge
AWM wideband o2 Question

What you're describing is installing a wideband controller, which controls the sensor's heater to keep it operating optimally. Your ECU also needs to control the O2 sensor heater, otherwise it will throw a CEL. Basically there is no good way to do this. You really should use a separate wideband sensor/controller.

Unfortunately he can't replace the upstream sensor (front, pre-cat) with anything other than another sensor. This is the one that is used by the ECU to control fueling.

 

Why not? As long as the dummie is reporting optimal riding conditions?

Then again... I do understand that those conditions may not always be optimal as the weather changes.

 

That's almost like blindfolding a person to walk down a familiar sidewalk, and telling them to start walking - they'll know their way down the sidewalk, but they won't be able to avoid any obstacles.

In turbocharged engines, particularly when a different turbo and tuning is installed, AFR is very important. It would be silly to give the ECU false information (for fueling purposes).

 

MetalMan, sounds right about the 2nd sensor needed for an AF gauge.

And no, I won't be putting dummies in ;-) At the very least, the upstream o2 is very important to closed loop fuel control.

Thanks!

 

this cannot be done on the upstream O2 sensor, if you do this the ecu will think the engine is running lean thus dump fuel and cause cel to occur.

to avoid stripping, start car and let idle, spray some pb blaster on the O2 sensor where it meets the bung. shut car off let let sit til its cooled to the touch. then put the socket on. you can also try tightening the sensor first( very little amount) then loosen it. <-- this would also break any corrosion weld.

 

Good call, hadn't thought to quench it like that. Thanks.

 

I was born in 94 so I wasn't able to experience the good ol days when there were no 02 sensors and cheap gas.