It varies on vehicle make and models. It does work on many cars (in the trunk, under the hood) but you should always test with your vehicle. Use the locations in the picture at the bottom of this page as reference. Your car may vary.

Because the phone picks up GPS signals from the satellites like other satellite systems (DirectTV for instance), it won't be able to get GPS positions while being indoors, underground or in tunnels. However, when used in car/truck, you can put it inside the glove box, it should have no problem getting positions. Keep in mind, your phone GPS chipset needs to "see" the satellites to work.

In downtown areas with high-rises around, due to poor sky view and signal reflection on the buildings, you may not get a GPS fix or get it with big margin of errors.

Cell Tower Fix

Beginning v3.1, there is an option "Cell Tower Fix" in the phone software (Motorola iDEN i### series phones only. Not available on BlackBerry and Windows Mobile). When this option is enabled and the phone cannot get a GPS fix from the satellites (because the phone is indoors or has poor sky view), it will then report the location of the cell tower it uses. When you view the tracking data online, these "cell tower fix" records will appear as red text on tracking history page.

Note: The location reported by cell tower fix is the location of the cell tower, NOT the location of the phone. It can be miles away from the actual location of the phone. Don't rely on it for the actual position of the phone because it only tells you the cell tower the phone is using at that moment. The phone can alternatively use different towers from time to time even it is staying in one place.

How does it work with geofence and speed alerts

Cell tower locations are not considered as your phone locations and are ignored when comparing with your preset geofences. Otherwise, it would trigger false alarms of your geofences, because the difference between the locations of your phone and the cell tower.

There is no speed data associated with cell tower locations so cell tower locations  are ignored by speed alerts. 

How does it work in reports

Cell tower locations are not considered as your phone locations and are ignored in tracking reports.

Tips:

"Cell tower fix" option is recommended to be set unchecked unless you would like to know the rough area the phone resides (for instance, you want to know roughly which town the stolen car is in order to file a police report, when the car is hidden inside the garage hence not able to get a satellite GPS fix).

To change the "Cell tower fix" option on the phone, from the AccuTracking main screen, press "menu key" on the keypad, then select "Setup..." > "Cell tower fix".

Car installation considerations:

Reference locations for car installation