Occasionally get a flashing a red light below a warning symbol (and beeping sound). I assumed I needed to empty water from the drain tube. But, after pulling the plug and even tipping the unit backwards, no water comes out. Don't know if there is anything I can do.

https://removeandreplace.com/2015/12/21/dishwasher-has-beeping-sounds-blinking-lights-how-to-reset/
Dishwasher lights flashing or blinking. The heating element heats up the water to operating temperature. If the water doesn't reach the proper temperature after a set amount of time, a light on the control panel might start flashing. ... If the drain pump is not working, a light on the control panel might start flashing. https://www.repairclinic.com/RepairHelp/How-To-Fix-A-Dishwasher/28---/Dishwasher-Lights-Flashing-Or-Blinking
Flashing lights and or beep sounds can mean the dishwasher problem was from a power surge or power outage. You can unplug the dishwasher from power or shut off the breaker to the dishwasher for 1 minute. This may reset the dishwasher and get it back to working order.
https://removeandreplace.com/2015/12/21/dishwasher-has-beeping-sounds-blinking-lights-how-to-reset/

sounds like the drain is plugged and wont drain all the way check the drain line and see if it is clogeed with something

Have you emptied the filter recently. If it's clogged, the machine can't drain or spin.

Is the water draining from the unit? It sounds to me like that symbol is telling you the water that has accumulated from removing the moisture in the conditioned air is full and needs to be drained.

Three main causes for water not draining are listed below:

1. Clogged drain tube - exhaust or relief tube the hose empties into (does not apply if hose empties into a sink)
2. Clogged drain hose - occasionally, debris from the wash will find it's way into the hose and clog, backing water up into the machine
3. Clogged drain pump - like the drain hose, debris gets jammed into the pump. It may take a while for the pump to accumulate enough debris before it clogs. Disconnecting the hose under the washer will occasionally leave enough room to dig out any clogs in the pump. If not, the pump may need to be removed to clear the obstruction.
   

Power light indicators on flashing red as warning that battery is almost depleted of functionality. ascertain that devices with extension cables deriving power from elsewhere are plugged in to reattain power to acheive regular functionality. For example, devices with red light indication as power warning would also flash yellow or green when in full power charge from another source. refer with devices user guide or manual for refering, diagnostics.

This is what the manual says:

When the internal water container is full, the back light on the LCD display flashes. The unit will shut off automatically, beep 15 times, and must be drained before it will restart.

To Drain the Unit: switch off the unit and remove the plug from the wall socket.

• DO NOT MOVE THE UNIT. Doing this can result in water

leakage, damaging your floor or carpet.

• Place the drain pan on the floor under the drain cap.

• Remove the drain cap and the rubber stopper from the

drain, and let the water run out. Partially fill the drain pan,

replace the rubber stopper, and empty the drain pan.

This procedure must be repeated until the unit is empty.

• Replace the rubber stopper and drain cap.

Put plug into the wall socket, and switch the unit on.

The warning signal should be off.

For Continuous Drainage: • Switch off the unit and remove the plug from the electrical outlet.

• Remove the Drain Cap and Rubber Stopper. Drain if necessary.

• Connect a Drain Tube (not included) (20mm / 3/4" inner dimension) on to the water outlet.

• Place the other end in a drain. Make sure the tube is free from twists and bends.

The tube must decline over its entire length.

check your fiklter is clean but drain machine first

hiya susand from what you are describing i assume your engine is diesel ? if so ? the symbol that is on is informing you that the diesel fuel filter is part fullof water do not panic? this is normal and there is a drain **** on the bottom of filter to facilitate drainage of water HOWEVER may i suggest you renew the fuel filter at this stage instead of just draining as winter is nigh and if filter has not been renewed for some time?? now would be good ? it is not expensive and if you know someone with mech knowledge /a friend? male or partner will save £££s on garage charge ? hope this helps and inspires you ?

I have the same warning light (and beeping) on my M6P09D2A. However, I could not get any water to come out of the drain tube. How did you get the water out??