Emissions code PO430 - Bank 2 Catalytic Converter Efficiency

[AlexDC]

About a month ago, I got a P0420 code and a mechanic talked me into changing Bank 1 cat, which I did with OEM parts. Check engine light went back on in a day after the change. Then the mechanic said that he had overlooked changing the two O2 sensors in bank 1, and did so. Check engine light stayed off for 2 weeks, but now I have a P0430 code (bank 2 cat).

Something is fishy here. I'm doubting cat 1 was bad at all. could it be just all the sensors being bad, given that changing bank 1 sensors seemed to last longer than changing Cat Bank 1? Could it be a leak? a dirty MAF sensor? More sensors gone bad? By the way, the car runs absolutely perfect with all the power, despite having 115,000 miles. Any help appreciated.

Thanks - Alex
2007 XC90 V8

[AlexDC]

I got myself a OBDII tool ... The only codes I get are PO430 (in fact I always get them twice, for some reason).

I clear the PO430 codes and they come back after about 30 miles of driving. The OBDII tool gives me the following FREEZE data:

Trouble code: PO430
Fuel Sys Sta B1: CL, using HO2S
Fuel Sys Sta B2: CL, using HO2S
Calculated Load: 40.39%
Coolant Temp: 90C
S.T fuel trim B1: 0.77%
L.T fuel trim B1: 9.36%
S.T fuel trim B2: 0.77%
L.T fuel trim B2: 7.8%
fuel pres. gauge: 483kPa
Intake M.A.P.: 57kPA
Engine speed: 1806rpm
Vehicle speed: 106k
Ignition Timing: 37.5o
Intake air temp: 22C
Mass air flow; 26.59g/S
Throttle pos.: 30.58%

Can you make anything of this data? B1 and B2 seem to be about the same in terms of fuel trimming. What is going on? Thanks a lot!! Alex

[jimmy57]

The fuel trims aren't what causes 0430 but they can be a contributor. The rear O2 sensor should be stable at steady load and be .65-.75 volts. Can you monitor rear O2's with your tool?

Make sure the intake damper system is working and the hoses are OK

[boosted5cyl]

Hmmm. I'll throw some thoughts at this and you can make of them what you will.
First thing, more of an FYI is that the threshold for cat efficiency is very low, something like 5% I think. Ie if your cat is at 94% efficiency, you can throw a code for it.

So did you end up replacing both of the sensors and the cat on bank 1 to "fix" it?

Since the banks share a MAF so I think we can rule that out for now. Same with a vacuum leak, its a possibility but I think right now that's further down the line.
Has the pre cat O2 on the offending bank been replaced? If not that might be my next port of call, the sensor might just be out of spec enough to cause the mixture on that bank to be out therefore causing the post cat O2 sensor as a result of the actual gasses passing by it, or the cat getting slowly coked up.

My recommendation would be to replace the pre-cat O2 sensor on bank 2 and attempt to clean the cats by adding laquer thinner to your fuel tank..

One last thought is that a leak in the exhaust, from the manifold down to and including the cat could also throw an efficiency code.

[AlexDC]

Boosted5cyl and Jimmy, thanks very much for very helpful leads!! I'll try changing both O2 sensors in Bank 2, as well as adding thinner to the fuel ... I understand it is about a gallon to a half empty tank and then running the car for about 150 miles at highway speed. By the way, bank 2 in a XC90 V8 is on the passenger's side?

Has anybody been successful removing a PO430 or PO420 code in an XC90 with these or any other methods?

Thanks and I'll keep you posted on results.
Best regards - AlexDC - 2007 XC90 V8 with 113,000 miles on it

[boosted5cyl]

Do the thinner first for the heck of it. At least that way you dont have to worry about gunking up a brand new downstream O2 sensor. I'm not 100% sure which bank is which on the V8...

[jimmy57]

bank 1 is frt 4 and bank 2 is back 4 on Yamaha V8.

[AlexDC]

Quick update: I took the equivalent of your paint thinner advise by adding catacleaner to the fuel tank. Check light was off significantly longer - instead of every 30 miles, it come back after 120 miles. I followed up with a can of BG44k and the light is still off after 160 miles. Please tell me if this means something to you? Just luck or we might be on the right track with the need for some cleaning? Thanks!

[boosted5cyl]

Its hard to say for sure but it's encouraging....

[aholt]

I know this is an old post, but just trying to see what ended up happening. I did a round of cataclean in fuel, seafoam in fuel & in vacuum line, and the code won't go away. Also replaced two O2 sensors on bank 2. Thanks