Our 3yr old Bosch dishwasher model SHX46A06UC/46 use to run +/- 105 minutes on the regular wash cycle. As of last week it runs 3-4 hours. What would your diagnosis be or what steps can I take to pinpoint the problem?

Check for water supply to the valve. Check for 120vac at the valve during fill cycle. If you have both, the water inlet valve is bad, part number 00425458.

Here is an excerpt from "Bosch Dishwasher Troublesoooting".

Running a Test Cycle
Bosch dishwashers have a test cycle which can be run as a troubleshooting measure. The method to run this test cycle is similar across the Bosch dishwasher range so if your dishwasher features seems different from those described below then try experimenting, as the process is fairly straight forward and will be very similar. Bosch dishwasher model numbers are usually found around the top or lip of the door. One of the most common differences between dishwasher models is simply the names of the buttons. For example in the first example below, POWER SCRUB PLUS and REGULAR WASH may be called WASH and ECO depending on your dishwasher model and the country you are in. The other key difference is whether your dishwasher has a display panel (which can display error codes) or not (in which case a program light will illuminate to tell you the fault.
To run the test cycle hold down the POWER SCRUB PLUS and REGULAR WASH buttons. Whilst held down press the ON/OFF button. The lights above them should flash. Now you can check the status of each dishwasher program by pressing its button. Now you can run the full test cycle = Press the POWER SCRUB PLUS and REGULAR WASH buttons again. The dishwasher will start up and when the cycle has ended one, if you have no display panel on your dishwasher model the indicator lights will illuminate if a malfunction was detected as follows -
CLEAN - A temperature sensor fault. If this is the case then the test cycle will be very short as the dishwasher will terminate the test once it's been detected.
RINSE/DRY - A water sensor/filling fault. If this is the problem then the test cycle will not complete as the dishwasher cannot detect the right level of water, the dishwasher will just keep filling and draining again.
WASH - A heating fault. Check your heating element.
If you do have a display panel on your Bosch dishwasher then after the cycle is complete an error code will be shown if a fault has been detected. The error codes are as follows -
0 - No errors have been detected.
1 - A water sensor/filling fault.
2 - A heating fault.
4 - A water filling fault. This can also appear as F on the display during a normal cycle.
8 - A temperature sensor fault.
When troubleshooting your Bosch dishwasher, running the above test cycle is a good start in diagnosing the problem and should give you an idea of where the problem lies with your Bosch dishwasher and what fixes and repair are in order. Our general troubleshooting page will give you some ideas on other things to check on your dishwasher. Good luck!

Elements Could be faulty, or timer on pcb could be sticking. I'd check elements first. Make sure they are clean and not scaled up and check for resistances

what is happenig i believe and has happened to me 2 times is that the water level float that is on the left side of dishwasher is stuck.

Either remove side panel and flick lever or pull dishwasher out and tap lower portion of panel and this will cause the level to move and then see hat happens

try running the test cycle or running delicate economy in that cycle it gets up to 150 degrees in the very first cycle let it run 15 or 20 min see if the water is screaming hot it is not and Luke warm it is not heating it is most likely a control board heaters very rarely go out

Try this link, http://www.applianceaid.com/boschDW.html for procedures for running self-tests on various Bosch models using the front door switches. Find your model and read and follow the procedure.
This remaining at '1' problem invariably relates to a 'heater fault' which has usually been traced to an open solder joint on the control board located behind the switches/indicator lights on front door. See pic here of open solder joint http://www.flickr.com/photos/zenzoidman/145089572/ In most cases, the heating element has not been at fault.
I got mine going again by resoldering the joint and saved ~$300 in parts & labour. If this is beyond your skill set, then replace the control board assembly, 266746, which is used on multiple Bosch models. See this page for more information if you want to try to DIY. http://www.appliancejournal.com/appliance-parts/bosch-appliance-parts/bosch-dishwasher-control-module-266746-37/

If this is still beyond your skill set, then call a tech & supply the Bosch model, serial number, and the results of the self-tests.

what is the model #?... there are 2 buttons when pushed together it will drain the water out..try the button to the left next to power scrub... and economy...hold the 2 buttons for 3 sec. you will hear you drain pump running.. if you don't hear any water draining out into your sink, you might have a clog d/w drain line.

I don't think you'll find it's the control board.
I think you'll find it's the heater box.
Not an easy job to do yourself unless of course you know what you are doing.
I would suggest you contact Bosch. One other possiblity is that the water inlet is blocked, although to be honest this is very rare.
Deep Diver

drain pump is running all time. cause is a leak. remove bottom front panel and mop out water or can also tilt at 45deg and water shud run out. machine shud then run but you then hav to find leak