Some useful info that can broaden your understanding about GPS working methodology :

1. satellite acquiring speed is slower when vehicle is moving, in the other hand mean u wan boost up the locking speed.. stop the vehicle at 1 spot rather than driving and waiting for searching

2. tinted problem.. some kind of Metal ingredient compounded tinted like " Vkool elite" will block the GPS signal significantly. signal will decrease 50%

3. running out of lane issue.. this is due to when switching destination.. did not click stop and write off completely..
(to overcome this, just simply off the wait for 10 secs jz restart)

4. when nearby high rise building like condo, satellite reception will be affected too. so prevent stay near to tall building when GPS is acquiring for satellite.
Some self check u may conduct for diagnose whether gps is working properly.

A. Keep your GPS in OFF mode, find a place with WIDE open air of sky ( maybe garden or playground). switch ON your gps, click the signal bar when enter main menu, user only TWO fingers to hold the gps up part & down part. DO NOT block the gps backsite antenna receiver (the black color part) see how long it takes time to acquire signal.

this method enable u to diagnose whether is the gps is faulty or other reason like tinted or moving that slow down your speed.

B. remember to "deactivate" (untick) other unused maps like thailand / indo/ taiwan (tools > setting > maps > info ) keep only malaysia map is active.

C. update the Map to the latest version
here : http://www.garmin.com.sg/mapupdate/

D. update the GPS software to latest
here : http://www.garmin.com.sg/softwareupdate/

hope this helps.. cheers