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O2 Sensor replacement gone bad

So my O2 sensor went bad on my car. I took it to the dealership thinking it was covered under my emissions warranty, but they said it wasn’t. The cost was around $400. I said I was going to challenge the warranty coverage but go ahead on the repair. They called me the next day and said that the threads on the catalytic converter had gone bad due to heating repeatedly and when the mechanics tried to remove the sensor, they stripped the threads on it. Suddenly my bill jumps to $1400 because they have to replace all these other parts. I asked if anything was covered under warranty and they said the catalytic converter was covered. The next day the warranty manager said it wasn’t covered because the O2 sensor is what caused the damage. My questions are: why isn’t that sensor covered under an emissions warranty? Who is responsible for replacing the damaged parts? By the way, while I was in there a mechanic came up the guy helping me and told him he broke clips on something and the car was going to need time to get new clips. Which makes me wonder if they screwed up the fix and are putting the charges on me.

Emission control sensors are only covered for 2 years/24,000 miles.

Catalytic converters/computers are covered for 8 years/80,000 miles.

Ask the dealership why they haven’t tried an O2 sensor thread chaser.

This tool was created to restore the threads when they’re damaged when removing an O2 sensor.


take your car to another shop asap…

Stripping the thread due to repeated heating and cooling is simply BS !!! As everything around the exhaust expands and contracts, the sensor’s threads will also. $400 for an O2 sensor installed is robbery.

The catalytic converter is a completely separate part. Why would it need replacing?

It sounds to me that someone messed up and they are trying to place the blame on the O2 sensor.

Read your warranty information carefully and see what is and is not covered. Sounds to me the car is relatively new.

$400 for a replacement O2 sensor sounds perfectly reasonable. Remember, dealerships (and most other quality shops) charge hours by the labor guide. 1 hour to diagnose, anywhere from .6 to 1.0 to replace the part (at $100-$140/hour), and $150 or so for an OEM Ford or Motorcraft sensor, you’re at $400.

If the threads in the catalyst are stripped I would try to repair the threads for a modest charge first. There are a number of tools out there that the shop should have to do so.

For some it is, for some it isn’t.

If your toilet is plugged and you don’t own a plunger or know how to use one, you will pay the plumber his $140 service call for him or her to clear your toilet. Would I pay that? No, but then I have a plunger and know how to use it.

I know this is water under the bridge . . .

Even if the threads are completely gone, I’m almost positive there are inserts available.

The oxygen sensor bung can also be replaced, in other words, a new one welded on

A competent exhaust shop would have been able to repair/replace the threads, without replacing the catalytic converter. Remember, the catalytic converter itself wasn’t bad, it was the threads, where the oxygen sensor screws in. They probably see this all the time.

Probably, the dealership wasn’t permitted to perform this kind of repair

Worst case scenario . . . the exhaust shop might have to remove the catalytic converter and do their repairs on the bench, if access is extremely limited. Still a lot cheaper than buying a new catalytic converter from the dealership.

Maybe the dealership guy didn’t use penetrant, before attempting to remove the oxygen sensor. Perhaps the threads can be chased and restored, perhaps it needs an insert or a bung

I’m with @asemaster on this . . . the dealership’s price is reasonable. No dealership is going to charge the same as an independent, with aftermarket parts and lower labor rates

I’m with the others and I don’t fault the dealer. Age, heat, and corrosion causes problems and many times the mechanic has no control over those problems.

The other day I changed the engine oil on a GMC Sonoma 4.3. No big deal, right? Almost 4 hours removing the oil filter involving 2 broken strap wrenches, 1 broken end cap wrench, filter pliers worthless, and useless 16" Channel Locks. Finally a 20" screwdriver, hammer, and cheater bar later it came off after holding on tight to the last turn of thread.

I was starting to think this was going to turn into a Dremel tool piece at a time job.

I think you may have just run into some bad luck there OP. It’s very possible everything the dealer shop told you happened, did happen. And while it may be possible to repair the cat problem with the threads bunged up like that, doing so may be illegal, or illegal if done at that location; i.e. it may have to be done by a state certified exhaust system repair shop, b/c the repair is emissions related as posted above. So the cost to repair may end up being more than just buying a new cat.

hmmm … if all that turns out to be the case, and checking with another shop for a second opinion is a good idea, probably best just to have it all done, and pay up. Grin and bear it in other words. You’ll end up w/a new cat and a new O2 sensor and should be good to go. If your Focus is more than 4 years old, suggest to find a well recommended inde shop to service it going forward. Dealerships tend to be geared up and specialize in servicing new cars under warranty. Older cars not under full warranty, that’s often not their priority.

The shop who installed it may have had a problem with an oil filter coming loose before, and grumpy customer asking for a new engine. So the shop owner would naturally at that point order their techs that whatever else may happen, oil filters must be installed so tight they will never come loose … lol …

Not so, definitely not illegal

So what year is your Ford Escape and how many miles does it have on it?
I’ve spent enough hours over the years struggling to remove corroded exhaust parts to appreciate that what the shop described may well be accurate. Heat and exposure to environmental factors often causes exhaust parts to fuse together for all eternity. Once that happens, the job can expand to needing to replace the “head pipe” that comes from the exhaust manifold to the cat converter and wherein most upstream oxygen sensors used to be mounted, and that can be a major PITA. Removing the pipe’s flange from the studs found on most applications after the nuts have welded themselves to the studs can cause the creation of entirely new swear words.

And cat converters are expensive. The platinum-palladium that the inner honeycomb is coated with is and alloy of very expensive rare elements, and the sputter-coating process used to apply it to the ceramic honeycomb surfaces of the cat-converter’s core is an expensive process. If Ford mounted the upstream senor into the entry flange of the cat converter, it may be impossible now to separate the two.

A second opinion is always prudent with an expensive repair quote, but if it were me I’d have the shop show me the problems they ran into and if it all looked reasonable, and they were using OEM replacement parts, I’d just let them do the work.

hmmm, maybe OP should call a plumber…cheaper :grin: