Not relying on bug detection the audio Jammer protects room conversations where sensitive information may be exchanged by generating a random masking sound that desensitizes any nearby microphone. The first place you want to check is under the hood.  If you see a set of alligator clips attached to your vehicles battery, you've probably got bugs.

Is your radio fuzzy?  Try to find a cable going from the car's antenna to the radio.  If you find another wire attached, bingo! That's probably it.

Look into each air vent with a flashlight to see if you can locate any hidden microphone which may be hidden inside.  You may need a magnifying glass to help you get a good view.

Look down beside the seats, on the back of the seats, under the visors and any other place that a microphone could be hiding.  This is important because a bug detector cannot find a signal if the transmitter isn't on.  The good news is that a microphone has to be exposed for it to pick up sound, so you can probably find it with a visual search if you are thorough enough. Don't forget under the seats and under the Dash!