Some times, the speedometer is at 20mph - codes P1330 and P1550

P1330 varible valve timming unit common problem to this vehicle and the P1550 is Vehicle Speed Sensor is produced by the ABS electronic control unit by averaging wheel speed sensor inputs and sending a digital signal via CAN bus to other modules that use the VSS. To test the ABS, a Volvo-compatible scan tool is necessary. If one is not available, the car should be sent to a Volvo dealer for ABS diagnosis. I can tell you however that most of the cars are fixed by replacing the ABS Control Module.

Code P1550 is a " by product" of some other code like an ABS code issue? You would need to scan the ABS module for codes to see what is going on? One problem I have seen is the left front ABS wheel sensor harness split open but is intermittant. You need to look at the harness really close especially at the bend. It splits open but you need to "bend" the wire at the curve to see if it split or not? Other then that you would need to post the brake control module code on here to see what is going on? If this is your vehicle Volvo will give you a free scan and diagnostic here is the link for more info

http://www.volvocars.com/us/top/yourvolvo/volvoserviceforlife/pages/default.aspx

Call Volvo to see if they are participating in the program and if you need to post the codes on here post them to get an idea as to what is going on with the ABS?

I am sorry I meant the right front sensor. But the left will also split once in a while. So check both fronts sensors at the front to be sure. For P1330 check the timing belt to see if it jump a tooth or two? If it is ok check the oil level. If low then that is your problem. If ok let it idle for about 30 minutes and pull the oil dipstick out while running and check the oil for oil bubbles. If the oil on dipstick is foamy with bubbles then the oil pickup tube seals are bad and you need to remove the oil pan and replace all the seals in the pan and pick up tube. If that is ok then the camshaft reset valve is bad. Try cleaning it out but most likely you will need to replace. Order it from the dealer and the new gasket will come with a screen to filter out the oil. Let us know what you find.