[isaiahgrose]

Hey guys,

I had a clogged catalytic converter on my 2005 GLS wagon, so I removed it and put in a delete pipe. Now it drives alright, but I'm getting the P1176 code. I put in a bent spacer on the back 02 sensor, but the code came back after driving for an hour. I'm wondering now if I just need to replace the back 02 sensor. Anyone have insight on this?

Also, it's been running a little loudly since I took the cat out. I know that's too be expected a little bit, but it sounds like there may be something else going on. Could that be related to the 02 sensor too? I'm wondering if it will affect gas mileage as well. Thanks!

 

[AndreasPassat]

Check your flex joints on the exhaust. Common cause of louder than normal exhaust. The back O2 sensor has nothing to do with how the car runs. It is merely there to check to see if the cats and are doing there job.

 

[Iowegian]

Fuel mixture is (partially) regulated by the front 02 sensor which I assume you retained. Rear O2 sensor just checks catalytic converter performance as mentioned above. Not surprised you are getting a P1176 with no cat but I have no experience with cat delete. You may need to re-program the ECU to ignore this error or just live with it.

 

[PZ]

Since it sounds too loud to you, I suspect the test pipe is leaking at either end. Fix that and see if the codes can be cleared. If not, the O2 sensor may be faulty. The flex pipe is far enough past the rear sensor that it should not affect the sensor unless it is torn wide open. On the V6, the flex pipe is in front of the rear sensor, so that is often the issue.

 

[isaiahgrose]

I replaced the upper half of the exhaust pipe (before the muffler) when I took the cat out because they were corroded together, so the flex joint should be okay. Do you know of anyone else who has experience with a cat delete?

How can I check if the test pipe is leaking? I have the 4cyl, so I don't think that's the issue, since I also changed the exhaust. Is it worth replacing the O2 sensor if I don't have a cat? If it doesn't affect the running at all I might just leave it, although I'd rather not have a CEL all the time.

 

[Iowegian]

The one and only function of the rear O2 sensor is to turn on the CEL to indicate your cat isn't working. It has no effect on the engine's performance.

I don't know of a way to 'fool' the ECM to not turn on the CEL so I think you would need to have that function programmed out of the ECM by someone who does that sort of thing. Or you could just open your cluster and remove the CEL light from the PC board inside but then you would lose all CEL's indications in the future.

 

[PZ]

On a cold, just started engine, run your hand around the outside of the exhaust connections. You only have a short time before it gets too hot. If you can do it without touching the surfaces, you may have 1-2 minutes, otherwise about 30 seconds. You will feel the exhaust blowing out. When the car heats up, there is less chance of it leaking.

You can try spraying bubble mix on the exhaust, but it might evaporate too fast.

 

[isaiahgrose]

Iowegian - I thought a spacer was supposed to fool it, but it hasn't worked yet. Would it work if it was just completely blocked off from the delete pipe, or does it need airflow?

PZ - I'll try that and let you know, thanks!

 

[Iowegian]

I have no idea how the ECM is programmed but I think the spacer is supposed to move the readings by some amount, not compensate for a missing cat. I could be wrong but unless you have access to the code inside the ECM we're all just guessing.

For example, the SAIP is only on for about 90 seconds and only after a cold start. Then later at some specified time, it is turned on briefly to test its functionality. Something as simple as a spacer is unlikely to fool the ECM into thinking everything is working correctly for that.

The downstream O2 sensor may be more simple or it may have multiple criteria that need to be met in order to prevent a CEL. It all depends on what the ECM program is looking for and having the cat completely missing could be enough that something like a spacer will not be enough. But as I mentioned before, I have no experience with a cat delete so I am just guessing. However, my gut instinct says that the ECM will probably detect that there is no cat in place and trigger a CEL unless that code is disabled by changing the ECM programming via a re-flash. Or you could just ignore the CEL as it will have no effect on how the engine runs.