How to Change the O2 Sensor

[Crystalgolem]

Hey all. I got a CEL yesterday and its P0172, System Running Too Rich, BANK 1. Called the Stealership for a quote on the O2 replacement...$240. $80 (part) + $160 (labor). Methinks thats a RIPOFF! If anyone can give me some how to's on this I would be much appreciative.

[paultakeda]

Which O2 sensor? Bank 1 has two sensors (the banks make sense for a V6, which has two banks, ours have but the one bank), the front and the rear.

Both are easy to replace if you can get under the car. You can simply unbolt the sensor from the exhaust and detach the wires connected to it. $160 for labor is a huge ripoff.

[Scarab 1]

Sounds to me like they are only replacing the front for you as well. For that total price you can order the Front and Rear and install them yourself. I only had to jack up the front passenger side a ways to get to them.....

[Crystalgolem]

Wow, so its not that bad? Should I go ahead and do both Front and Rear?

[Oyveychris]

That quote is for 2 hours labor. There's no way that there's 2 hours involved. Even if I had never turned a wrench, I could do both in under an hour.

[Scarab 1]

Yea, there is no way I would pay for the 2 hours....once you get the car up in the front passenger side you will be able to get to BOTH Front/Rear and once you get through one the second one will be even easier!

[Too Cold NB1.8T]

There is only one bank on a four cylinder.

This is a fuel trim fault and it may not be a bad O2 sensor causing this DTC, also, that $240 quote is probably for a replacing the sensor and resetting the ECU.

Before spending any cash on a new O2, I would make sure that this isn't being cause by an engine mod(s) or a bad FPR MAF sensor etc.

[Crystalgolem]

The CEL is off now...no reason why, I dont have any mods and havent done anything to it...i had $$ set aside for sensors, should i get a Forge DV now? or should I wait a while and see if the CEL comes back?

[Too Cold NB1.8T]

Replacing the stock DV is a good idea, I would recommend a Baileys DV for the best direct replacement style but either way you should be OK to replace the stock one with a quality DV of your choice.

[Too Cold NB1.8T]

FYI, when it comes to service or labor, the dealer usually goes by "book time" and includes time for everything involved with that particular service, this is normally only an estimate.

The actual charge is normally less than the estimate because the time it takes the technician to perform the service is usually less than that listed in the book, this is something that the vehicle owner needs to clarify with the service writer and not assume.

[Crystalgolem]

Ok so I installed the new DV, and a couple Hoses (all looked fine). Cleaned the MAF really good and replaced the spark plugs. I though the problem was solved. Once I get running things are smooth. But it has a really rough idle immediately after the crank, if I dont give it a quick rev it will die every time. Does this point to a bad O2?

[Too Cold NB1.8T]

Once the car has been driven through enough cycles for the Readiness codes to pass, it would be helpful to know what the Idle and Run adapt numbers are in group 032 (fuel trim).

It is possible that one or both Oxygen sensors have failed but as I mentioned in an earlier post, P0172 is a DTC that reflects a fuel trim problem, this could be the result of a cause other than a bad oxygen sensor.

Replacing the plugs and carefully cleaning the MAF sensor with at least 90% Isopropyl or MAF sensor cleaner are great things to do, however, it is possible that the MAF sensor isn't just dirty, it might have just failed and this cannot be determined by simply unplugging it.

If you're going to try and diagnose/repair the problem(s) at hand as well as any future issues that may arise, you will need a vagcom.

[Scarab 1]

Yea I agree...I am sure there are new codes. Get those and go from there! This is a helpfull link sometimes:
http://www.elitedubs.com/text/index.php?topic=988

[Crystalgolem]

I have the Shareware VAG-COM software and an Ebay cable. What other info do I need to diagnose this problem besides the codes it has already pulled? Random Missfires in all 4 cyl. and Bank 1 Lean.

What are Readiness Codes, and how do I scan for the Idle and Run Adapt numbers you speak of?

[Scarab 1]

I am very new to the Vag-com software. I will let someone else field that question. Have you chipped the car?

[Crystalgolem]

Originally Posted by Scarab 1

I am very new to the Vag-com software. I will let someone else field that question. Have you chipped the car?

Same here, I just got everything running yesterday, although its not the Full Version, its still VAG-COM Software, so it should be able to pull all the info...

The car has no mods at all. Stock everything, except my new DV.

[Crystalgolem]

I forgot to mention P0172 is gone and I now have P1127, (too Rich)... Possible Fuel Pump Relay problem.

[Scarab 1]

Well, if I have to put a guess out there you have a vacuum leak or the MAF is shot...
Does the car idle higher than normal now?

Can you log with what you have?
see this -
http://www.ross-tech.com/vag-com/cars/fuel-trim.html

[Crystalgolem]

Originally Posted by Scarab 1

Well, if I have to put a guess out there you have a vacuum leak or the MAF is shot...
Does the car idle higher than normal now?

Can you log with what you have?
see this -
http://www.ross-tech.com/vag-com/cars/fuel-trim.html

Good Link. I'll check bank 032 when I get home and report bad tonight. ;D

[Too Cold NB1.8T]

Both P0172 and P1127 relate to a fuel trim "Too Rich" condition so it wouldn't be a bad FP relay, you can't guess here because this problem could be caused by a number of things.

You should have the complete Ross-Tech vagcom software & cable in order to begin a proper diagnosis on these cars, the Readiness codes are what set letting you know that the ECU has gone through enough cycles to be dialed in, it takes approximately a few days of multiple driving cycles for it to set and if things are right here, all areas will show as "Passed".

Group 032 is fuel trim data, this tells what the percentage of ECU fuel adjustment is for both the Idle adapt and Run adapt (off Idle), the numbers in this block will tell you how much the ECU is having to adjust for a lean or rich condition, this is very very important information.