Ok my nav system would sometimes read the disk and sometimes show error reading disk. So I took the Nav player out and cleaned the Lazer eye

1/ Undo the rear light cover inside the trunk/boot two butter fly nuts.
2/ Remove the battery cover.
3/ Pull the carpet cover surround from around the dvd/cd players. Be careful not to damage the shape to much and look for the white root release pull cable.
4/ Turn ignition ON, open the Nav DVD front and press the green eject button to remove the nav dvd.
5/ Undo the right side brass 2 10mm bolts holding the Nav/power amp/CD frame in place. This helps when removing the stack unit.
6/ On the left side remove the two white wire harnesses (press top and pull) and the single grey plug. These plugs have a little arrow on them that should face up when re inserting.
7/ Remove the 3 8mm bolts one on top 2 on each side near the top. Now pull forward the 3 units from the frame and remove the harnesses from the back. 2 in the back of the nav dvd + a plug and a grey connector.
8/ Undo the 4 screws each side of the nav and cd player. Then slide the NAV player out.
9/ On a work bench with good light remove the 6 screws from the nav unit 2 back 2 sides and 2 holding plastic tabs each side. Lift case of unit.
10/ You can see the dvd unit. There are 4 small screws holding the black plate on top. Before removing these on the left side there is a leaver that connects to the top plate and is
held on with a small pink tab that has a slit. Use a thin knife/razor blade to gently slide this off.
11/ I recommend taking pictures of the front and side of the player there are springs and leavers on the cd loading edge (front) that my pop out of place during the next stage.
12/ Now undo the 4 small screws holding the black plate in place and gently leaver the plate up. Start at the front. DONT yank it off gently remove!!
13/ At the back under the spring loaded plate the holds the center of the dvd you will see the lazer eye. This needs to be cleaned.
14/ The lazer eye is on a worm screw and will need to be pulled back along the runners. Gentlty pull on the housing to move it back towards the back of the player.
15/ With the eye in view use Acetone on a quetip to clean the eye. I applied the acetone and used compressed air to dry if off. DO not rub with a cloth!! If you
do not have compressed air let it air dry. It should look clean as whisle under a magnifying glass!! Note there is no potentiometer adjustment on these players.
16/ Also clean the two disks at the center that hold the disk these are coated in a black grippy paint. DO not use acetone to clean these as it will remove the paint.
17/ Installation is the reverse i.e black plate (insert back screws first then firmly press the front it should click into place insert screws), side leaver blah blah.
18/ When its all back together and with the ignition ON press the eject button before inserting the nav dvd. Mine did not worth the first time and I had to re-clean as above before it started working.

Good luck.

 

Also I needed to burn a new DVD as they oxidize middle layer after a few years.