Sherlock Investigations is often called to sweep vehicles.
Eavesdropping devices placed in vehicles are often dormant. A hidden cell phone is hard to detect unless it is active, or transmitting.
There are two types of GPS trackers, active and passive. An active GPS device signals where the car is at all times. It has a built-in cell phone that calls the person who placed it about every two minutes and can be tracked via a computer.
One has to actually retrieve a passive GPS unit. When it is connected to a computer it shows where the car has travelled.
Usually, GPS units only operate when the car is moving. This is meant to save the life of a battery. So, if you’re looking for a GPS on a vehicle and it is parked, there is no movement, and so the GPS unit is dormant.
The best way to sweep a car is physically. A hand-held mirror is a good tool to use. (Be sure to get a plastic one, in case you touch any wires.)
The search should be done everywhere. Under the seats, in the glove compartment, under the dash, under the fabric in the back window etc.
Under the dash there are many wires and devices you have probably never noticed before. Check for wires that are sloppily installed and do not seem to be installed by the factory. Look for extra wires going to the antenna.
Sit in the driver’s seat and look around. Check the overhead map light, and the air vents. What you are looking for is a tiny microphone.
Next, check the undercarriage of the car. A GPS unit is usually attached by a magnet, or several magnets. It will be in a black plastic box, perhaps the size of a pack of cigarettes. (Google "GPS units" so you know what to look for.) Move around the exterior of the car carefully looking in every spot of the undercarriage.
This is best done if you have a mechanic put the car up on a lift. The mechanic can then help since he knows what belongs there.
Make sure to inspect the grill and the bumpers. Remember, GPS devices can be very small.
If you have questions, or need a professional sweep, contact me.