1999 V70XC 2.4L 5cyl turbo with 352,700 kilometers (approx 220,000 miles) Canada car.
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
- MAF
- 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 about this!

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!

I'll give this a few more weeks to really see if this has fixed this 4801 code. This car still has the original MAF and the ETM is the original white label part, too. I am hoping I do not have to get into these for what would be yet another grand...

 

we are considering buying a well kept 1999 xc70 with only a error code showing up froma the engine light diagnosis; dealer suspects needs a new ECM soon , but this is way too costly for the point of having small budget to buy a 99' vehicle; so can you
suggest any thoughts on ignoring the engine light, the idea of replacing ECM, or a place that sells them less costly and who to install software download- besides dealer ?

 

I would suggest posting this as its own thread as you may catch the attention of someone who has experienced the exact same situation.

My 2 cents?
Get the error codes read by an independent specialist that can tell you exactly what the code(s) are.
In my experience an ECU either works or it does not - they do not show serviceable wear like something mechanical and "be on their way out".

Be nice to your indy specialist and they will likely help you out to determine if your is a fatal (expensive) situation or not.

 

Oh, and post the code!