Volvo

The firt thing I recommend is having the computer scanned. If the check engine light is on, the computer has a trouble code stored in it that should lead you to the problem. Many parts stores will scan it for free. Have that done and let me know what you find.

Joe

Sounds like a few possibilities, let me know the following;

The vibraton under load, is that when the brakes are applied or load on the motor?

The Diagnostic Warning lights on the Dash Diplay are the brakes/ABS system?
The Check Engine light?
Did any of the vibration preceed the odometer failure, etc. Give me a chonollagy of the sequence of events or the abrupt onset of symptoms,

I will check for your reply to this post and get back ASAP.

Sounds like you could have 2 different problems. The ABS light could also trigger a check engine light. Most probable cause of the failure for the ABS light giving the fact that it is affecting the trip mileage, will be a defective ABS module. On this model year it looks like it is still a plug and play unit, meaning there is no software required to download but you would need to calibrate if this has Dynamic Stability Traction Control (DSTC). It still will be a good idea to check with the parts department? For your vibration under load, does the check engine light flash when it vibrates? If it does then you have a misfire. Usually the coils go bad but you would need to verify that by having the ECM scanned for fault codes to see where the misfire is at, and while running gently lift up on the suspected coil but do not pull out completely, to see if you can feel it igniting and you should here it popping each time. If there is no misfire codes, have the axles checked, when the joint starts to fail they will cause a vibration under load as well.