(2003 S80 T6) Recently had cyl no.s 4 and 6 ignition coils quit. Unwisely drove it home about 10 miles. Replaced coils, no problem there, but then got a p 430 error code (cat threshold efficiency bank 2). Started simple, looking for vacuum leaks as suggested by local Volvo independents and discovered a small crack in the charge air pipe. Glued that closed even though I believe that would not cause the code. Still got code after a few driving cycles.
I assume the unburnt fuel that may have been fed into the cats could have ovheated them. I say may have because I would think the system would have shut those injectors down when it detected the misfire.
Anyone know if it can do this?

Pulled off the cats (as an experiment to see how much trouble) and found no big rattles but there is a fair amount of sand like material that will shake out and looking in the end of the last big cat it's grid appears about 30% filled.
Is that enough to say it is done?

I will probably get new o2 sensors while I'm at it but one big snag: I can not find the connectors for the upstream O2 sensors. If they are where I think they I can not see them or reach them.
What is the trick to locating these darn connectors and then getting at them? (I have access to a lift.)

Thanks for any help.

 

To get better access, take off the front driver tire. They clip together very oddly. Be sure you know which connector corresponds to the O2 you're replacing because all four are in the same area.

 

Thanks 537, I'll give that a try.

 

Tried removing wheel to gain access to o2 connectors. At least I can see them, but still can not reach them and separate the connectors. This should be simple, what am I missing?
Does anyone have first hand experience with this who can describe how to access and disconnect these, please?


Also just to keep this current, when I put the exhaust back on I swapped the bank one and two rear sensors to see if the code would follow the bank two sensor or stay with the cat. I am trying to conclusively determine the cat is bad before dropping 1300 bucks on a new one.

Well now after a few driving cycles I get codes that the front sensors are bad as well. I guess just taking them out and handling them was enough to upset the system, or my swap trick is flawed somehow. Of course their cables were twisted as I unscrewed the sensors, which could have damaged the cables. Way too sensitive. No wonder these cars are such a mess.

I guess Now I have to swap the rear sensors back and see if I get back to just the p 430 code, and will try to measure back pressure to conclude if the cat is clogged. I did try vacuum test to look for back pressure but I can't tell what normal should be like on this car so that is inconclusive at least for me. Anyone have a good vacuum test procedure for this car? I know it can tell a lot but need to know what normal looks like. Would probably be a good first test for many issues I see in these forums.

Thanks, hope my frustrations are at least somewhat subdued here.

 

Okay, thanks for the tip, got the connectors apart. Found a lot of debris in one of the connectors. It was a very fine sand like material. Cleaned and put back together to test if that makes any difference.
I realize I failed to mention in the original post that along with the codes for cat threshold efficiency the car has been running fine but with no boost from turbos. I suspected the plugged cat was the cause of this lack of power but have now tested backpressure and found it to be pretty normal: <1 psi. So I now suspect the compressor bypass may be faulty.
Does anyone know where that device is located on this engine? It is not mounted on the compressor housing as in most applications, at least mine has no such unit on the housing.

Thanks

 

Just Ohm out the O2 sensor and see if it is broken down in side and how much it had.

Those connectors on these cars are very easy compared to the other models.

$1300 is way too much to pay for an o2 sensor.