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Lemur BlueDriver OBD-II scan tool review: BlueDriver diagnoses engine problems, shows smog check readiness

OBD-II diagnostic device BlueDriver interprets engine error codes to suggest what might need fixing, and lets you know if your car is ready for a smog check.

Wayne Cunningham Managing Editor / Roadshow
Wayne Cunningham reviews cars and writes about automotive technology for CNET's Roadshow. Prior to the automotive beat, he covered spyware, Web building technologies, and computer hardware. He began covering technology and the Web in 1994 as an editor of The Net magazine.
Wayne Cunningham
5 min read

The complexity of modern cars, with their computer-controlled fuel injection systems, spelled the end of the shade-tree mechanic. Unless, of course, the diagnostic tools used by professional mechanics become inexpensive enough and easy to understand for the average Joe.

LemurMonitors BlueDriver

Lemur BlueDriver OBD-II scan tool

The Good

Repair Reports generated by the Lemur BlueDriver not only interpret error codes, but suggest causes and fixes. The Smog Check feature can let you know if your car is likely to fail a smog test.

The Bad

The BlueDriver app offers no help in understanding your engine's running data. A built-in VIN scanner would be a helpful addition.

The Bottom Line

For its price, the BlueDriver is a convenient tool for those who want some ability to work on and understand modern engines.

That's the idea behind Lemur Monitors' BlueDriver OBD-II scan tool, which lets you check your car's engine performance, examine error codes, turn off a check engine light, and even get an idea if your car will pass its smog check.

Affordable OBD-II scan tools have been around for a while, but BlueDriver allows for deeper data and more portability. Instead of an integrated scan tool with a small, monochrome LCD, like the majority of models available, BlueDriver consists of an OBD-II dongle connecting to a smartphone through Bluetooth. The BlueDriver app allows for a large number of features and takes advantage of a smartphone's computing power and connectivity.

BlueDriver turns your smartphone into an engine scan tool (pictures)

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Some of the data shown by BlueDriver will be incomprehensible to the average car owner without the help of a site like OBD-Codes.com. Lemur Monitors includes features that make BlueDriver more generally useful, however, such as smog-check readiness and repair reports.

OBD-II plug

BlueDriver's black plastic casing measures 2.25 inches long and 1.75 inches wide (57 by 45 mm), large enough to accommodate the OBD-II plug on one end. This dongle will plug into a car's OBD-II port, which is usually placed under the dashboard on the driver's side. On my own 1999 BMW Z3 Coupe, however, the port sticks out in the passenger-side footwell. Lemur Monitors molds a convenient finger grip into the top of the BlueDriver, making it easy to insert and remove.

Note that OBD-II ports were mandated for 1996 model year cars and later, so the BlueDriver won't be much help on that '86 Plymouth Reliant in your driveway.

LemurMonitors BlueDriver
The BlueDriver app's Live view shows real-time diagnostics from your engine. Wayne Cunningham/CNET

The free BlueDriver app runs on iOS and Android devices. The home screen includes icons for the main functions, while a strip along the bottom offers a shortcut, labeled Live, to view the data stream from your engine. A secondary menu screen includes icons for the BlueDriver manual, customer service, and ordering the BlueDriver dongle.

To get started, I plugged the dongle into my car's OBD-II port, then opened my phone's settings and accepted the Bluetooth pairing. Launching the app, I chose the Vehicle Info icon and entered my car's VIN, which brought up detailed information about my car. The app also let me choose year, model, and make -- useful if I didn't have the VIN handy. It would be handy if the app offered a VIN scanner, using the phone's camera to recognize the VIN on the car.

Firing up my car, I went to the app's Live function and was able to see which OBD-II data points my car generated, and could choose which of those data points appeared in the app. These data points include such things as engine load, intake air temperature, and oxygen content of the fuel mix. With my data points chosen, I could watch the data stream in real time on my phone.

The app shows colored graphs for each data point, which look cool but are not particularly useful. More to the point are the numbers generated in the Live view, but the most useful feature is the ability to upload the data as a spreadsheet. The resulting report isn't pretty, but formatted as comma-separated values, most spreadsheet programs can parse it.

The values shown in the Live view and report will only prove meaningful if you have some expertise in OBD-II diagnostics. As a helper, the app has a Freeze Frame function, which captures the running data when the engine throws an error code.

Code interpretation

For the novice, the app has a Read Codes function, which interprets error codes from the OBD-II port. You can also use the Clear Codes function to reset a check-engine light, but if the underlying problem is not fixed, the engine will just throw the code up again.

LemurMonitors BlueDriver
BlueDriver's Repair Reports interpret error codes, and show possible causes and fixes. Wayne Cunningham/CNET

Based on any error codes received, the app can generate a Repair Report which interprets the code, shows what might have caused it, and offers potential fixes. These Repair Reports are a highlight of the app -- they're like having an experienced mechanic at your shoulder. My car was not throwing any errors, so it didn't generate any reports, but the app showed an example. Lemur Monitors gives five Repair Reports for free with the app, and only charges 99 cents for each five additional reports.

The most broadly useful feature of BlueDriver is Smog Check. No, this is not a full smog test of your car. Rather, the app looks at engine data which might cause a car to fail a smog test. Not only does it look for the Check Engine light and error codes, but also examines engine compression and spark data. BlueDriver cannot tell you if your car is going to pass, but it can give you a pretty good idea if it won't. My car got a green light from the app, suggesting I could take it in for a smog test with little worry.

And as a handy extra, the BlueDriver app even includes a flashlight feature, making use of your phone's LED flash, for when you are digging around the engine or looking for that elusive OBD-II port under the dashboard.


At $100 (which converts to around £59 or AU$106 -- and Lemur Monitors ships internationally), the BlueDriver offers a lot of insight into how well your car is running for a cheap price. Using an app interface rather than the fixed electronics of most OBD-II scanners lets Lemur offer more features and make reading the resulting data easier. Better yet, the app can take advantage of a phone's connectivity to interpret error codes and get the latest fixes from Lemur.

As BlueDriver is focused on automotive repair, it does not offer any fuel economy information or driving coach, like the Automatic driving monitor. Instead, it will give people who want to tackle their own engine maintenance a means of tracking trouble. Some of the data goes deep, but that can give novices an entry to learning much more about how modern engines operate.