siegen

My CEL came on with code 17524, which is B1 S1 oxygen sensor (front/upstream, right side). The sensor is not accessible from the engine bay, but is readily visible from beneath the car with the belly cover off. Problem is, I can't fit a socket on the oxygen sensor because of the catalyst's heat shield, which sits very close to the hex on the O2 sensor. I purchased this tool from Autozone, but it won't fit over the hex due to the heat shield. Even if I were to grind the outside of the socket down, it wouldn't fit.

The way I see it, the only way to do this is to remove the catalyst completely (with both O2 sensors in the catalyst) and then use an end wrench on the O2 sensor when it's all out of the car. Before I do this, does anyone have any other ideas that I could try?

The A4 3.0L O2 sensor seems to be one of the most difficult O2 sensors in the automotive world. If I do end up having to remove the catalyst to replace it, I'll try to do a write-up with pictures. I read a guide with pictures on replacing the upstream O2 sensor on the A6 3.0L, but it isn't the same.

siegen

For those curious, it did require the near removal of the catalytic converter. Took 5.5 hours, including time driving to the store to get the correct tools and some lunch. Could probably do it in 3 hours now that I know what to do and what tools to use. Having access to a better vehicle lift would speed things up further.

The airbox and some surrounding parts had to be removed to access the upper nut that attaches the catalytic converter to the exhaust manifold. This was the single most difficult part (the two lower nuts are easily accessible from beneath the car -- all 13mm). After unbolting the catalytic converter from the exhaust manifold, removing the bolt that attaches the cat to the chassis, removing the clamp on the exhaust pipe, and then routing both O2 sensor wires down, we were able to pull the catalytic converter out a ways and get an end wrench on the O2 sensor to replace it. The CV joint shield also had to be removed to give more room to move the cat around.

I'm not sure if all catalytic converters are the same, but the reason I couldn't replace the O2 sensor with the cat still bolted up is because the heat shield, which is attached to the cat, makes it impossible to get any sort of socket around the hex on the O2 sensor.

Unfortunately I didn't get any pictures, though everything is pretty easy to see through the whole process.

The good news is that replacing the right upstream O2 sensor did alleviate the problem (no more check engine light). The dealer wanted $700+ to do it. Including the cost of a 13mm flex socket, I spent $96 total (O2 sensor from AutoHausAZ).

2003 Audi A4 3.0L Quattro 6MT 65k miles

CEL Survivor

2004 Audi A4 (B6) V6 3.0 Quattro 150,000 miles

Code 17524 Bank 1 Sensor 1 oxygen sensor precat driver side O2

I did it this way too in a very similar process and it took about 5 and a half hours. Did everything for just above $100 to include socket set. Here are some pics.

paul85

I need to do this same repair this week. I get the P135, heater malfunction on B1S1 which will necessitate removing the sensor. I am going to try an open end wrench after soaking the threads in pb blaster and maybe I'll get lucky.


Looks like I can get the sensor for just under $100 from amazon.com.

paul85

Actually, I'm going to try the cheaper alternative. Was reading this up on the 1.8T guys O2 sensor thread and it's said that the cheaper alternative should work for our sensor also. I ordered the 17014 part and Powerbuilt 648691 Oxygen Sensor Offset Puller.




From the thread @ Cheap: $40 O2 Sensor - DIY
"Any chance you can find a similar replacement for the Bosch 17353 O2 sensor? Those are what is used for the front 3.0 sensors. I'd like to replace mine at some point, but the $100/each price tag and needing two of them is a real downer to getting them done.

But if I was a betting man, which I am, then I would say the 17014 sensor should work on the 3.0 as well. The 17353 shows to be a compatible replacement part with the 1.8L beetle and the 2004-2006 TT Quattro. Coincidentally the Bosch 17014 also shows to be compatible with those too models. Try it at your own risk, but IMO I could take the chance..."

paul85

FYI, the cheaper sensor works fine on the 3.0 for B1S1. I swapped out the defective one for this generic wideband (swapped over the connector as well), and the engine light is gone. Wiring harnesses are the same length so there's no need to lengthen it like the 1.8T guys do.

Saii94

how do u take off the y pipe next to the coolant temperature sensor

turbo510

Maybe there are easier ways to do this, but I changed those front sensors while the intake manifold was off. I had a coolant leak under the manifold, which was due to a bad O-ring. While that was off, I changed the two heater hoses, thermostat, and all four O2 sensors. Even with the plastic coolant distribution manifold removed, it was still a chore to change those front sensors. You can look right at them, but they are still difficult to get a socket on. But they are installed, and no more CAT codes, plus the car gets better mileage.

Fahrvergnugen

Sorry for the thread revival, but I saw one picture that I can not find now from underneath, RF axle removed... Looked like the 02 was more easily reachable from that angle? I'm hoping someone has tried that before and can report back. TIA