I replaced the ABS module this evening. I received no ABS message after starting the car, but it sometimes takes several hours or days of driving to occur. I now have a check engine light, the amber triangle, and "Engine System Service Required". Does anyone have any ideas on what could be causing this? I removed the air box and disconnected one electrical plug from the airbox. Other than this I only disconnected the ABS module.

"Engine System Service Required" message and amber triangle indicator have gone away now. Only have "Check Engine" light.

A dealer needs to plug the car into their Vadis PC to read, then clear the code(s).
If you turned the ignition on with that MAF sensor plug disconnected, that's why the check engine light is on but it won't clear by itself. Disconnecting the battery, fuses etc won't work either so don't waste time trying.
Do be sure to tell the service writer that you think that you caused the check engine light so that (assuming you're out of warranty?), they won't think you have a defective MAF sensor.
BTW, as for S80s and ABS control units, S80s do not share the same control unit problem that 850s, X70 do share. It's likely that your ABS problem was caused by something else.

Thanks for the information. I did start the car with the sensor disconnected so that sounds reasonable. The dealer said that he read a code indicating that the ABS module needed to be replaced. I am holding onto the one that I removed in case the ABS light comes back. Are the codes as explicit as the dealer indicated. In other words, what type of descriptions does the VADIS system return? Thanks.