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XC90 T6 4801 catalytic converter problem

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XC90 T6 4801 catalytic converter problem


Old 10-22-2014, 12:16 AM
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Join Date: Jul 2012
Posts: 1
Default XC90 T6 4801 catalytic converter problem

I would like to start by saying I have done research on this code but it typically seems to coincide with other codes. All I'm getting is the 4801 code. The car is a 2004 xc90 t6 with 170k. Earlier this year my ETM became intermittent on a road trip. Through much problematic driving I was able to get home. I replaced the throttle body and gasket. Shortly after the replacement I began getting the 4801 code. I figured my front bank o2 sensors must have been ruined by the rich fuel mix from the bad throttle body so I replaced both front o2 sensors with oem Bosch sensors. After using my European specific scan tool (cant remember the name off hand but its not a run of the mill generic scanner) to clear the code, it popped back up after about 30 or so miles of driving. I am probably going to go to the shop some time this week and have my guy take a look. Do you gents have any ideas what it might be and where I should recommend my mechanic start. Just don't want to go to deep in the hole if I can help it. Also wondering If maybe it could be as simple as a new software update

Thanks for any help

Additional Info
synthetic Rotella
new coils and spark plugs less than 10k
new throttle body less than 10k
new O2 sensors
cleaned MAF
plastic turbo hoses that run over top of engine 10K
average fuel economy 17mpg on only premium
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Old 10-23-2014, 10:34 PM
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Join Date: Sep 2014
Location: Vancouver, BC
Posts: 17

Hey nstrom91, I just cleared up this same issue on my 1999 V70 XC.

Mine is a few years older but all the research I did seemed to point in the same direction.

2.4L 5cyl turbo with 352,700 kilometers (approx 220,000 miles). Check engine light was on and code was read as "ECM-4801 Three-way catalytic converter (TWC) efficiency, bank 1.

Searching all the Volvo sites seemed to indicate this could be a few things:
- pre & post o2 sensors faulty
- catalytic converter could be toast
- Fuel injectors
- vacuum leak on intake side or exhaust leak

All of these could be an issue for me based upon mileage plus my cat rattled like it was broken inside when I pounded on it with my fist...

I knew I had an exhaust leak so I started there.
Re & re'ed exhaust manifold from the top. Not fun... Plus my turbo was worn out - the vanes were scraping the housings on both sides! Got a low mileage turbo with reasonably tight bearings and in it went.

This fixed up my exhaust manifold leaks at a couple of the ports but still had exhaust leak. The downpipe flange was difficult to bolt up and after checking this w/o the heat shield on was not sealing at all!

The down pipes on this model is a diabolically designed piece of &%$T! The engineer should be shot with a ball of his own ****! This thing should be two pieces!
You need a hoist to take it out plus need to drop the subframe.

With this much work I was going to replace the cat too! A 1-piece bolt-in was far too many CDN$'s so I elected to have an after market welded in plus replace BOTH the pre & post O2 sensors at same time. With the DP out it was evident that my leak was a broken weld around the flange from the turbo side (flange is tacked in a few places on the backside).
I figure this broken weld is likely due to my son putting this car in a ditch a few years ago...

I had the cat guys weld the flange on too and back together it all went. Code has been clear for 3 days now PLUS mileage is approximately 25% better. The exhaust even smells way less rich at the tailpipe at idle and the exhaust fumes in the car are GONE and it is QUIET! VERY happy!

Not a cheap fix, tho. Welded in cat plus 2x O2 sensors plus some shop time on a hoist to wrestle that pig out was just over CDN$1K with our brutal taxes!
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