Idiot lights. Hate them, hate them, hate them! Especially the &^%$*# “Check Engine Light”. Did you know that the Check Engine Light can come on just because the gas cap is loose? Who’s brilliant idea was it to put a light on the dashboard that can come on for everything from a major engine emergency to a loose gas cap?

Enter CarMD. This is a small, easy to use device that can do quick or in-depth readings of why that light is on.CarMD comes with the reader, a USB cable, the CD, quick start guide, and a nice embroidered nylon pouch. (Do you tend to judge a product by things like the quality of the pouch or CD label? I sure do. Not always a fair thing to do, but this is one nice pouch!)

Using the tool and the software is truly ‘easy peasy’. Plug the device into your 1996 or newer car (and the website tells you exactly where the port is for your car), turn you car’s electrical system on within 10 seconds of plugging the unit it, and wait for it to chirp four times.

The CarMD Reader

The ‘red/yellow/green’ LEDs on the front of the reader will light up to tell you if your car would likely pass, possibly pass, or probably fail an emissions test.

Create an on-line account (CD or downloaded software) and plug the reader into a USB port with the included cable to get a detailed account of what the codes mean, even to estimated repair costs in some cases.

CarMD on-line

I tried it on one of our cars, and a car in a company fleet. My car got a green light and the company cars got a yellow. The report was quite detailed for the two codes listed under the yellow light issue- it did not pinpoint ONE cause, but rather gave an unweighted list of what it could be.  For example, one code, P0135, had this name: “HO2S-11 (Bank 1 Sensor 1) Heater Circuit Malfunction”, gave us these conditions: “DTC P0101-P0103, P0106-P0108, P0112, P0113, P0116-P0118, P0121-P0123, P0125, P0128, P0201-P0206, P0410, P0440, P0442, P0443, P0446, P0449 and P1441 not set, IAT and ECT sensors with 11ºF of each other at startup, MAF sensor less than 17-20 g/sec, HO2S signal within 100 mv of bias voltage at startup, and the PCM detected the HO2S signal remained within 150 mv of bias voltage (450 mv) for 50-80 seconds (depends on ECT and MAF at startup).” and these possible causes:

• HO2S heater ground circuit is open or has high resistance
• HO2S heater power circuit is open (test O2S fuse in fuse block)
• HO2S heater element is damaged or has failed
• PCM has failed

The fleet manager said this was consistent with a bad O2 sensor (or O2S), which was a suspected problem with this vehicle. It is important to note that the CarMD does not even claim to find everything that might be wrong with your car. I know my car has problems with a couple of the electrical systems, but there was no indication of that on the report. CarMD, like most of the ‘plug-in diagnostic tools’, mostly focuses on emissions-related issues.

CarMD comments that the tool would be useful when buying or selling cars, preparing for trips, etc. It would also be useful for a small fleet manager, etc. except that it only manages three vehicles and up to six reports a month per CarMD tool (in other words, they do not offer extensions, etc.)

As a potential car buyer you need to remember the limitations of the tool- it does not check everything, or replace the usefulness of things like CarFAX reports or good mechanical look-overs, or tell you to do routine maintenance, or offer advice on improving mileage.  It also does not reset any codes or clear the idiot light itself- you still need the mechanic for that.

The company itself helps overcome some of these things- they offer useful forms and checklists, advice, phone support if you cannot plug into a computer (such as in a car lot), and more. I am quite impressed with their on-line and other support. They do not charge for looking up codes, there is not a subscription fee or anything, and they seriously seem to be trying to be helpful to us plain consumers. Very refreshing!

Bottom line- for under $100, this is a well-made, easy-to-use, user friendly device that does just what it is supposed to and does it nicely.

Filed in categories: Car Gear

Tagged: auto, Car, diagnostics, emissions

CarMD Vehicle Code Reader Review originally appeared on The Gadgeteer on June 1, 2009 at 3:00 am.