sgoff61

Please bear with me as I am trying to get information for my brother and don't have first-hand knowledge, but I will try to provide as much detail as possible.

First of all, we're talking about an '05 xB with high mileage due to a long daily commute (probably about 170K, mostly highway) and no modifications.

His problems started about 3.5 years ago when the serpentine belt broke and the CEL, VSC and Trac Off lights came on. (As we understood it, the VSC and Trac Off lights came on only because the CEL was on, so we assumed that the main problem was the CEL.) The first code he got (through Autozone) was for one specific coil pack, so he replaced that. Lights went off for a few hours (if I remember correctly) and came back on. Took it back to Autozone and got a code for a different coil pack, so he replaced the other 3. Lights went out and came right back on, and the code this time was for the first coil pack that he had replaced, so he gave up for some time, but cleared the lights several times by disconnecting the battery and every time they came right back on.

Back in March of this year, he started trying more aggressively to correct the problem because he knew that he couldn't get the emissions inspection with the CEL on, but nothing worked. Plugs and wires were replaced, air filters....everything maintenance-wise. Eventually he was told that Autozone's scanning was limited, so he finally found someone else to scan it and wasn't given the specific codes but was told that it was either the camshaft position sensor or the crankshaft position sensor. Considering the location of the crankshaft position sensor in relation to the broken serpentine belt, we decided it was the most likely culprit so he replaced that one first. Lights went out, but came right back on within a few minutes. Disconnected the battery to clear the lights, but again they came right back on before he could even get to the inspection station a couple miles away. Then he replaced the camshaft position sensor and had the same result.

By this time, his tags had expired and he couldn't get the emissions inspection, so I borrowed money to help him get it fixed and we put it in the shop. I have no idea what was done that time, but I do remember that they said that there was no code for the catalytic converter, but that it may be "hidden" behind the other codes and could show up after the other codes were cleared. Once the work was done, they said that there was still no code for the catalytic converter but if it was bad, the code would show up after he had driven it a while. He managed to get the emissions inspection and renewed his tags but, sure enough, the lights came back on within a couple of weeks so we took it back to the same shop. This time, they said that the catalytic converter needed to be replaced, so I borrowed money again and we had it done.

Before long, the lights were back on again and he was getting misfiring codes (I don't know what they were), but he didn't want to go back to the same shop and I was hesitant to offer anymore suggestions because I felt responsible for suggesting that shop in the first place so he just dealt with it for the next few months. I'm not sure, but he may have replaced the MAF sensor during this time. Then, a couple weeks ago, his transmission went out so he took it to AAMCO. Initially, the plan was to rebuild it, but it turned out that they couldn't (something about internal gears) so they ended up replacing it with a reconditioned one, although I don't think that makes any difference regarding the lights. Anyway, they pulled the codes for him and, without giving him the numbers, told him that it was misfiring on cylinders 1 and 3.

Ever since the lights came back on after the catalytic converter was replaced, people had been telling him that it was probably the O2 sensors. He has never been given any codes specific to the 02 sensors, but he finally decided to replace both of them so we ordered them and they came today. Now people are telling him that, since the O2 sensors were not replaced along with the catalytic converter, that the sensors may have ruined the new catalytic converter and that, if he replaces just the sensors and the catalytic converter is bad, that it will then ruin the new sensors. In other words, they're saying that the catalytic converter and O2 sensors always have to be replaced together and that either one being bad will cause the other to go bad, so now he is afraid to change the sensors without making sure that the catalytic converter doesn't have to be replaced also.

So, now that you have the whole story, at least as I remember it and understand it, here are my questions:

1. Is it true that bad O2 sensors can ruin a new catalytic converter and vice versa so that both always need to be replaced together?

2. If not, is it safe to replace just the O2 sensors and see if that solves the problem, or would he be better off to wait and have the catalytic converter checked again?

3. I read somewhere that catalytic converters are usually under warranty for 8 years or 80k miles. Would that likely include replacements, or just the original? (He was going to check the paperwork from when it was replaced when he got home tonight, but I haven't heard back from him yet.)

4. If the catalytic converter is still under warranty, could it be voided if the O2 sensors were bad when it was replaced (although there's no way we could prove that)?

5. And finally (I think), if the catalytic converter is still under warranty, would he have to take it back to the shop that replaced it, or could he take it somewhere else based on the possibility that they may have caused the problem by not replacing the O2 sensors at the same time? (If that turns out to be the case, I know he would not be comfortable letting them work on the car again.) Or, as another alternative, is there any way he could get a new catalytic converter under the warranty and replace it himself?

Thanks in advance for any help or insight, and please accept my apologies for such a long post.

Reactor

First of all it is true that you'll never have a code for bad Cat if you have some of the other fault codes active. Like for bad ignition coils, misfire, bad O2 sensor, MAF etc., because ECU doesn't even try to check the Cat if it knows that something else is wrong. So when everything is fixed and codes are cleared you start driving it and soon the P0420 pops up for the bad converter. Totally possible.
Only the front O2 sensor has any effect on anything. The rear one is only for verifying the Cat operation. But i'd expect the bad O2 sensor to set the CEL on long before it can become bad enough to damage the converter.
Factory Cat is warrantied for 8/80. Aftermarket depends on the place that installed it. They'll usually try to decline free replacement if they didn't diagnose it and it was only done on your request, if there are other engine related issues present, etc. Did you install OBD2 approved converter BTW?
List exact fault codes you had. Sometimes people get them mixed up: bad coils mistaken for misfire, VVT solenoid for the camshaft sensor, etc.
Hope the engine didn't get overheated when the belt broke.

sgoff61

Thank you!

We didn't doubt that the code for the cat wasn't showing up until after the other work was done, we were just concerned about the fact that the O2 sensors were not replaced along with the cat based on what others are telling him now. As for whether or not the new cat is OBD2 approved, I have no idea as I only payed the bill and my brother took the paperwork home with him. I do know that the cost for just the cat and labor was a little more than $700, if that is any indication. I wish I could remember exactly what was done the first time (before the cat was replaced), because that bill was just under $2000. And by the way, they did diagnose the cat. Looking back over my records for the loan, it was just 6 days between the first repair and replacing the cat, and we assumed that the cat was the problem when we took it back since they had told us that the code might show up later, but they did pull the codes and verified that the cat was definitely bad.

Unfortunately, I don't have any of the codes now. I know that he was given the actual codes each time he took it to Autozone, but those little printouts can be confusing to someone who doesn't really know what they're doing and the employees can sometimes be quick to offer their opinions without really understanding it themselves, so I was also concerned that the codes had been mixed up at some point, especially when we replaced the coils. And the last time the codes were pulled (at AAMCO), he said they didn't give him the codes but just told him it was misfiring and, since so many people have mentioned the O2 sensors, he decided to give that a shot. If it were me, I think I would have considered dynamite by now, but since that's really not my call, I think I might have to get him a code reader for Christmas. LOL

And the car definitely did not overheat when the belt broke as he knew it the moment it happened. He basically pulled it off the road and into a parking lot and called me, I picked him up and took him to get the new belt and he replaced it right there, so the car really wasn't driven at all until it was replaced.

In any event, spoke to him a few minutes ago, and I think he has decided to go ahead and replace the sensors and see what happens. I may be naive (scratch that... I KNOW I am), but I can't imagine that there could be too many other things he could still need to replace. I just wish one of us had the money to take it to the dealer and tell them to call us when everything is fixed. I really miss the days of being able to jump the starter with a screwdriver, testing the thermostat in a pot of boiling water, etc. In other words....no electronics! LOL