OBD Fuel Saver—Even the Scams Are Getting Tacky

For several years, scammers have been selling gadgets you plug into the on-board diagnostics (OBD-II) connector now installed in most automobiles which claim to save fuel, increase performance, stop hair loss, or other benefits. Here are three such devices presently for sale on Amazon.com:

How can a little dongle that plugs into what is a mostly read-only data port possibly save fuel (or “fule”)? Well, of course, it can’t. This is a total scam. All the thing does is draw power from the car (even when the ignition is off, for most) and blink LEDs which are suppose to make you think it’s doing something. Some monitored pins on the OBD-II port and blinked with packet traffic to make it look more persuasive.

The material that comes with the scam plugs warns motorists not to expect an immediate increase in fuel economy, as the device takes some time to “learn your driving habits and optimise itself for your particular vehicle”. Presumably the owner will have forgotten entirely about the gadget by then and not realise they’ve been fleeced.

Now, Big Clive has taken apart one of the latest generation of these devices. Gone is the microcontroller which used to make the LEDs blink semi-randomly. Gone is the connection to the data pins on the connector. All that remains is a two-transistor astable multivibrator making an LED blink and a button that makes it stop blinking when pressed, which is supposed to make the mark think it’s resetting and re-establishing communication with the car.

It’s a race to the bottom, even among scammers!

A commenter on YouTube suggests that they should also make one that claims to improve the sound quality of your car stereo system and market it to audiophile rubes who pay hundreds of dollars for special HDMI cables.


P T Barnum……


Here is a competitor to the do-nothing box in the original post where the “creators" went to some effort to obfuscate what is going on. This one has one of those eight pin penny a pop microcontrollers driving the LED light show with something that looks like data flowing on the CAN bus and an utterly bizarre three transistor circuit that implements a push button on-off toggle for the microprocessor. When you take it apart, you discover that the circuit board includes connections to the SAE and CAN bus pins, but if you follow the traces (including some obfuscated by through-holes beneath the switch mounted on the top), you find they don’t connect to anything. The designers even included a polarity protection diode, presumably because the target market for devices like this includes a substantial number of people likely to install their car batteries backwards.