Liftgate does not stay up,why?

Something has likely fallen between the top of the liftgate and the cab. It will be the space above the seal. Use a clothes hanger or something similar to remove the obstruction.

there are two hydraulic cylinders that normally hold the gate up. likely the gate was pushed open hard in cold weather, popping the seals in the cylinders. you will need to replace the cylinders. then, do not push the lift gate up to open it. it should be able to rise by itself. if it does not, you can gently ease it open slowly.

REPLACE THERMOSTAT IF TOP COOLANT COOLANT HOSE GOING TO RADIATOR IS HOT TO TOUCH THERMOSTAT OPEN. TO BLEED COOLANT SYSTEM FIRST YOU NEED TO ADD COOLANT TO THE COOLANT OVER FLOW JUG UNTIL COOLANT LEVEL STOP DROPPING AND STAY AT FULL COLD MARK.WAIT 3 MINUTES IF COOLANT DROPS ADD MORE COOLANT UNTIL COOLANT STAY AT FULL COLD MARK.WITH RADIATOR OVER CAP OFF CRANK ENGINE FOR MINUTE WATCH COOLANT LEVEL AT OVERFLOW JUG.IF COOLANT DROPS ADD MORE COOLANT IN THE OVERFLOW JUG.WHEN COOLANT LEVEL STOP DROPPING IN OVERFLOW JUG.SCREW BACK ON THE RADIATOR CAP TO OVERFLOW JUG.WHILE ENGINE IDLING WATCH TEMPERATURE GAUGE WHEN TEMPERATURE START CLIMBING TURN OFF ENGINE WAIT A WHILE KEEP FROM GETTING SCALDED.WHEN COOLANT COOL DOWN SOME. PLACE A LARGE RAG OVER THE COOLANT OVERFLOW JUG OPEN CAP LITTLE AT A TIME UNTIL PRESSURE RELEASED, THEN REMOVE CAP ADD MORE COOLANT IN THE OVERFLOW JUG TO THE FULL COLD MARK.THEN REPEAT THE PROCESS SCREW BACK ON THE COOLANT OVERFLOW RADIATOR PRESSURE CAP.THEN START ENGINE WATCH TEMPERATURE GAUGE WATCH COOLANT TEMPERATURE GAUGE WHEN COOLANT TEMPERATURE START RISING TURN OFF ENGINE AGAIN WAIT UNTIL ENGINE COOL DOWN ENOUGH TO KEEP FROM GETTING SCALDED TAKE PLACE LARGE RAG OVER RADIATOR CAP WHICH IS THE COOLANT OVERFLOW JUG CAP OPEN CAP LITTLE AT A TIME UNTIL PRESSURE RELEASED ADD COOLANT UNTIL AT FULL COLD MARK. WHEN YOUR COOLANT LEVEL STOP DROPPING.AND TOP RADIATOR HOSE VERY HOT THERMOSTAT OPEN AND AIR IS OUT THE COOLANT SYSTEM. MAKE SURE YOUR COOLANT OVERFLOW JUG HAS COOLANT IN IT,WHEN ENGINE COOL DOWN CHECK COOLANT OVERFLOW JUG KEEP COOLANT LEVEL AT FULL COLD MARK.BECAUSE IF OVERFLOW JUG IS EMPTY THATS A SIGN RADIATOR COOLANT LEVEL LOW.WHEN OVERFLOW JUG EMPTY IT WILL ALLOW AIR GET IN THE COOLANT SYSTEM AND CAUSE CAR TO OVERHEAT.WHEN REPLACING THERMOSTAT ALSO REPLACE THE RADIATOR CAP ON THE COOLANT OVERFLOW JUG.

FILL COOLANT SYSTEM UP BY POURING COOLANT IN THE EXPANSION TANK UNTIL COOLANT LEVEL STOP DROPPING IN THE EXPANSION.WHEN YOU POUR COOLANT IN EXPANSION TANK AIR BLEED OFF THROUGH THE SMALL COOLANT LINES GOING TO EXPANSION TANK.WITH PRESSURE CAP OFF RADIATOR COOLANT LEVEL IN EXPANSION IS AT FULL COLD MARK.WHAT YOU TO DO CRANK ENGINE UP LET IDLE WARM UP UNTIL COOLANT DROPS IN EXPANSION TANK KEEP ADDING COOLANT UNTIL STOP DROPPING STAY AT FULL COLD MARK.WHEN COOLANT LEVEL START RISING IN EXPANSION TANK.PUT PRESSURE CAP BACK ON RADIATOR.WHILE ENGINE IDLING WATCH TEMPERATURE GAUGE.IF START CLIMBING TURN OFF ENGINE LET IT SIT FOR LITTLE WHILE TAKE A LARGE RAG OPEN RADIATOR PRESSURE CAP A LITTLE AT A TIME TO KEEP FROM GETTING SCALDING TO RELEASE AIR IN COOLANT SYSTEM.WHEN PRESSURE IS RELEASED OPEN PRESSURE CAP ADD MORE COOLANT IN THE EXPANSION TANK.CRANK ENGINE AGAIN LET IDLE WHEN TEMPERATURE GAUGE START CLIMBING. TURN OFF ENGINE WAIT FOR WHILE BEFORE OPEN RADIATOR PRESSURE CAP.WHEN YOUR THERMOSTAT OPENS WHEN TOP RADIATOR HOSE IS HOT AND ENGINE COOLANT TEMPERATURE GAUGE STOP CLIMBING AND COOLANT LEVEL STOP DROPPING IN THE EXPANSION TANK.ALL AIR IS EXPELLED FROM COOLANT SYSTEM TO KEEP ENGINE FROM OVERHEATING.

Hi Code P 0217 does point to the thermostat but it also points to the wiring, cooling system, and the temperature sensor, to check the thermostat start engine then once the temperature gauge in the car reaches normal the thermostat should open and the top hose that goes into the radiator will warm up quickly as the thermostat opens, if the thermostat is stuck in it's open position the top hose will start warming up before the engine reaches it's working temperature, hopefully i have explained it clearly,

needs new lift gate struts

It sounds like the inner latch that is bolted onto the gate itself is either off centered or the spring is gone. You can replace it easily. You can pick one up in a junk yard for a couple of bucks. To replace just open the hatch and remove all screws from the panel. Then pull the panel toward you to pull the clips from the body. once the panel is loose, push the panel in an upward motion toward the roof of the vehicle. This will expose the latch itself at the top of the opening between the glass and the gate. remove the latch wiht a 10 millimeter socket and replacew it with the one you just purchased. Try closing the glass very slowly before tightening fully. Replace the panel.

The thermostat is starting to stick .
Replace the thermostat.

Check to make sure your thermostat works right by monitoring the warming up of your engine. With a completely cold engine, start and run the engine for a few minutes, then put your hand on the top radiator hose to monitor if and when it gets warm as the thermostat opens more and more and note the gauge reading( if it works) the top radiator hose should be unbearably hot within 5-8 minutes. If the therm. opens right it should close right aswell, staying open a little while eventhough the radiator may have cooled may be what you are experiencing causing the rapid cooling and is nothing to worry about. The Hose should not get warm very soon after starting the engine. Regarding you gauge, lets take one step at a time, verify proper op. or the therm.

coil spring:
buy/rent a spring compressor.
hook it upside down over the second last coils of the spring(second last coil of the unbroken part) (bolt heads down and accessible) so that the compressor clears the spring seats.
Use all parts of the compressor.
Do up the spring compressor till it is just tight.

Put the car up on a 2 post, as the load comes off the suspension the spring will tighten in the compressor and flop around loose on the strut. Unbolt the top strut mounts. lower the axle until there is clearance and lift the spring off the strut.
Slowly take the tension off the spring compressor
Put the new spring in the spring compressor, (second last coils to clear the spring seats when reinstalling).
tighten the spring compressor, evenly and compress the spring, till it fits over the strut.
lift the axle, bolt on the top strut mounts, slowly release spring compressor, ensure top n bottom spring coils seat in the spring seats.
lower two post hoist
test drive

Always replace springs together as a pair