What is an EMP Weapon:

The Electromagnetic Pulse (EMP) Emitter was a weapon disguised as a camera used by the Lemons to sabotage the World Grand Prix and discredit its use of Allinol in Cars 2.

"This camera is actually an electromagnetic pulse emitter."
—Professor Zündapp

While on the large oil field owned by the Lemons, Agent Leland Turbo first discovered the device and passed his findings to Agent Finn McMissile before being captured and killed by the Lemons. McMissile went to the oil field, where he saw the camera from a distance and snapped photos for analysis.

The camera, described by Professor Zündapp to be an Electromagnetic Pulse Emitter, was used to kill Rod "Torque" Redline when he was filled up with Allinol. During the first leg of the World Grand Prix in Tokyo, Lemon lieutenants Grem and Acer used the camera to explode WGP racer Miguel Camino's engine before spotting Mater in Lightning McQueen's pit, recognizing him from the bathroom as the one who interacted with Redline. The camera was used to blow up the engines of two additional racers: Rip Clutchgoneski and Max Schnell

Grem and Acer used the camera during the second leg of the WGP in Porto Corsa, Italy, to explode the engines of racers Carla Veloso and Nigel Gearsley, causing them both to spin out. Agent Holley Shiftwell, from replaying the crash, detected a strong electromagnetic pulse and tracked it to the camera she found to be the same one McMissile had found earlier. After McMissile's attempt to stop Grem and Acer from damaging any more racers resulted in McMissile's capture, the two lieutenants continued their usage of the camera, which they utilized to blow up another racer Shu Todoroki's engine, leading to a huge pileup involving five racers.

During the third and final leg of the WGP in London, Grem and Acer, from inside Big Bentley, used the camera on Lightning McQueen, but nothing happened as McQueen had switched from Allinol to Fillmore's organic fuel prior to the race, prompting the lieutenants to switch to the backup plan, which involved a bomb that was planted in Mater's air filter. The weaponized camera was presumably disused following the arrests of the Lemons and their boss, Miles Axlerod.

Source:Pixar Wiki

Note

It's not a weapon. It's just decorative.
Also, it didn't have blueprints or detailed pictures so it doesn't look like the real thing.