On a previous post, I told about the $1300 we spent to replace the mass airflow sensor and electronic throttle module. Then two days later, the right turn signal would not turn off, then both turn signals quit working altogether as well as the sound system and cruise control buttons on the steering wheel. So THANKS to a response telling me to pull fuse #22 & replace it after a few minutes, for the steering wheel module, the signals and steering wheel controls now work, for a whole week now, did that repair last Sunday, a week ago. Since then, the warning lights "ABS Brake Service Required" "Brake Failure Stop Safely ASAP" + "Check Engine" "ABS" and the icon showing a car in a skid have come up. Then a day after that it says "Emission System Service Required" + "Check Engine". The dealership is scheduled to look it over under the supervision of Volvo Corp. after we pleaded for some assistance with this car and they responded with the offer to help us. But NOW, since Friday, NO warning codes are coming up at all! I drove the car Friday, Saturday and today, Sunday, and not a single warning code is coming up. Does anyone think that there's really NOTHING wrong with the car and it's just a malfunctioning computer? I now wonder if the computer caused our mass airflow sensor and electronic throttle module to not work and we paid 1300 for nothing... With no codes coming up right now, I wonder if the dealership can find anything tomorrow. We know that car though, our luck won't last for long, warning messages will return, it's just a matter of time.

Also, we're almost due for the 60,000 mile maintenance and they charge over $600 for this!! Is it REALLY necessary? What more can be wrong with this car after they do that check??

Thanks!

Yup sounds like an ABS Controller problem.

As others have stated these cars are overly complex in the electronics dept (16 seperate computers talking over a CAN lo/hi speed network).

This model is the first Volvo have tried all this new technology in (Complex CAN networks, transverse mounted engine+autobox etc); in other words the earlier S80's were in my opinion essentially mass produced test vehicles; hence all the nightmares people have suffered with the gearbox, electronics etc.

This may have improved in later models but I suggest you do what im doing; get rid of the car asap or be prepared for some serious spending if something fails out of warranty (more a question of WHEN than IF really IMO).

Dont get me wrong these are brilliant to drive etc. but full of potentially expensive gremlins.

I agree that you need to perform the maintenace that is recommended in the manual. Way too expensive to gamble.
You are right on suspecting a computer to be at fault. But I'm not sure if you suspected the ABS/STC Control Unit. This Unit has the inherent design flaws from the 850 and 70 series.
It has a life span of about 5 years or 60,000 miles. When it fails, it triggers a problem code in the other computers since the wheel speed signals are routed through the ABS unit first.
Here's the information I have collected on this subject.
Vitor's ABS Web page
Click on the ABS / TRACS Repair link.

My volvo is suffering the same error messages/lights. I think the electronic failures are cuased by inferior computer boards/parts and/or bad QC. How could Volvo accept such parts from their supplier? The Japs do have a better QC.

Believe it or not, your problems are typical of many '99, '00 S80s and there isn't just "a computer" but several and too many actually. The car's an overly complex, networked "beasty" (being as nice as I can be realistically).

"Also, we're almost due for the 60,000 mile maintenance and they charge over $600 for this!! Is it REALLY necessary?"

The 60K service is a good idea and it's essential that your serpentine drive belt (NOT timing belt) be replaced at that mileage because if it breaks, it often burns through the t-belt cover, takes out the t-belt too and valves hit pistons (will run over $3,500 to repair). The 60K service isn't even close to $600 at our dealership, more like less than $400 complete but maybe they have a higher labor rate that us? It's 4.5 hours for a T6 S80 by us, 4.0 for a NA 2.9 model plus parts as listed in your maintenance manual check guide.

The ABS problem is probably a bad ABS control unit (common) which then triggers both a check engine light and trans error codes too because they don't see a signal from an ABS wheel speed sensor. For an S80, that control unit costs about $650 now plus labor.

"What more can go wrong?"
Unfortunately LOTS of things, the trans can fail (not unusual), many suspension problems (typical), more electrical problems, I could go on........