Just to add to what others have said, there is nothing on the Volvo that will tell you when to change the transmission fluid, codes or other wise. The yellow dip stick is a nice back drop to monitor color change in the fluid. When the fluid turns brown it's because it has oxidized, and should be changed. Your milage may varry but 20-30K is about it. I have seen lower milage transmissions that needed flushing and higher milage transmissions that still had nice pink fluid, so monitor your own and take action as needed.

Ken,

Even though your owner's manual does not list changing the transmission fluid on the maintenance chart, follow Charles' input on this issue. Volvo has issued a TSB on the subject and will flush the fluid on cars within warranty if they exhibit a rough disengagement of overdrive (apparently a sure sign that your tranny fluid has been 'stressed'). This started to show up on my car at about 46K.

If the records don't show that the transmission fluid has been changed, I'd do it ASAP. Good idea to have it all flushed. Then, if you are using non-synthetic, change what is in the pan every 15,000 miles. If you change it all to synthetic, then change what is in the pan about every 50,000 miles.

Ideally, the fluid should be changed often enough so it never shows signs of breaking down. Fluid is a LOT cheaper than a transmission.

I always have mine changed every 20-30k miles. Its probably overkill but hey. Whenever I get a new car I always have all fluids flushed and replaced. Its cheap insurance and then you know for sure when it was done last. You should flush your tranny fluid once every 50k. Do not wait till it smells burnt or gets smokey.