Here is my problem....

In MAY '09 my '95 850T set codes of 2-3-2 and 4-4-3. I knew that the first code was from vaccum leaks and old rubber elbows. The second code is for low cat converter effciency. I remember getting this code when the front O2 sensor was dying. That was back in '04 when the car had 100,000 miles.

I live in California and needed a smog check and had a plan to replace the rear O2 sensor since it was the original. Replaced the elbows and the sensor and it passed smog...no problem. Neither code returned and the performance was smoother and more responsive.

Made a trip to the desert and stayed for 4 months where I did a major tune-up, tranny flush and replaced the heater core. She ran like new and I made several trips through-out New Mexico in 100+ degree heat. It never missed a beat.

On my return to Northern California in SEPT. '09, I made a stop in Los Angeles and the check engine light came on. I wasn't worried that I would be left stranded as the car was running just fine and I felt no difference in performance.

After arriving in NOCAL, I checked the codes and the 4-4-3 returned.

HAS ANYONE EVER HAD TO REPLACE A CAT CONVERTER ON AN 850? Is that really the problem for a car that has 165,000 miles?

If it is the problem can the cat converter be cut out and a new one welded in place or should I have to replace the WHOLE exhaust system? I've seen the muffler and pipes and it's still very solid with no holes or rust of any kind.

Has anyone had this kind of issue(s) and is something else to blame for the cat converter code.

Thanks,

Dan
'95 850T Wagon
165,000 miles
ALL Stock

Take it to your mechanic and (s)he should be able to use a pyrometer and probe the 'inlet' and 'outlet' temperature of your catalytic converter. Based on the probed temperature difference, (s)he could tell you whether the converter if fine or not (it is simple chemical engineering reasoning, and I happen to be a chemical engineer). My mechanic did exactly that (it takes a couple of minutes or so) ~2.5 years ago when I had the same code, and indeed it turned out that my cat converter was fine, while the O2 sensor was the suspect. After having the O2 sensor replaced, I have had no codes or related issues ever since.

BTW, the dealer was getting ready to replace my cat converter, since they 'were not sure whether it was dead or not'.

Good luck!

'95 850 turbo sedan (180k miles, bought it new 15+ years ago,and it still flies like new)
'06 S60 (29k miles, bought it new, and my other half drives it happily)

Clear your code and remember how long it takes to come back. You could have gotten some high sulphur gasoline which coats the sensors a little(?). Did you ever replace the rear O2 sensor? Were the Sensors after market or OEM, it does make a difference.

Klaus
--
Proud owner of a 1967 220S. If I had more room, I would have more Volvos.

Both sensors were purchased thru IPD and were/are BOSCH. Doesn't this company make O2 sensors for every car on the planet?

Correct, but not everyone buys Bosh.
The DTC points to the cat because the difference of what the forward O2 sensor detects and the rear O2 sensor detects. The only way to definitively answer the CAT question is to hook the car up to a monitor and watch the O2 sensors do their thing.
Because your car is running good, the CAT is not blocked, it could be just a dirty front O2 sensor. Or it could be a bad CAT, which does happen depending on the fuel supplied. Any amount of lead will kill it at this age - I know, there isn't supposed to be any leaded gasoline in the USA. But large amounts of sulphur will also coat it badly.

Klaus
--
Proud owner of a 1967 220S. If I had more room, I would have more Volvos.

Klaus,

Just this week, I actually cleared the code and it ran like shit. Seemed to be gasping for air at times, especially when you are slowing down and come to a stop. The code came back within two days.

The front OS sensor was replaced at 100,000 miles in 2004 and the rear is just a year old when the car had about 160,000.

I won't clear the code again (until the problem is found) because it runs better. I guess the ECU is doing it's job!

Thanks,

Dan

Did you read the other thread where someone else is having an O2 problem? Clear the code and disconnect the battery for 10-15 minutes. That causes the ECU to relearn and should improve drivability a lot.

Klaus
--
Proud owner of a 1967 220S. If I had more room, I would have more Volvos.