1996 Lexus ES 300 Long Term Road Test

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1996 Lexus ES 300: Checking Fault Codes with CarMD

August 22, 2012

1996 Lexus ES 300

Before we bought our 1996 Lexus ES300 a mechanic looked things over physically and ran a full diagnostic that uncovered no fault codes. Later on we lost a MAF sensor, but at the time we were shopping it hadn't yet started to fail and spit codes.

In those early days I confirmed the mechanic's findings with this CarMD code checker. On the one hand I was curious about this device and on the other I wanted to see what it would say about our new Lexus.

Confirming what the mechanic had said, the CarMD came back with a green light, which means no OBD-II fault codes. But the CarMD goes beyond other retail fault-code checkers, mainly because the company that makes this device also makes a lot of the professional diagnostic equipment used by mechanics, and has been doing so for many years. Snap-on is one of the brands they supply, for example.

And so a green light here means a lot more because this device looks beyond to items that fall outside the narrow emissions mandate of the OBD-II rule. And a green light here means no stored historical codes, no ABS codes, no air bag codes.

In other words, a green light here says a lot more than the absence of a fault code with other readers, such as the Scan Gauge II we've used previously. In the event any of those non-standard codes are found the CarMD turns on its yellow light. A Scan Gauge II in the same circumstances won't say a peep. 

If you do get a yellow or red light, this device is made to plug into your computer for more information. And you can do this hours later, away from the car, because the data stays in the device's memory until the next scan. 

If you have a code it will present the definition in plain language and will list likely causes and possible repair costs based on a statistical analysis of what has previously been the trouble that triggered that particular fault code in your year/make/model of car. The analysis is derived from root-cause repair reports from participating mechanics around the country that have been using the company's pro-level diagnostic tools for years.

Is it perfect? Probability and statistics deals with likelihoods, not certainties, so the answer you get is never to be treated as gospel. Any number of root causes could turn out the culprit, and this device can only make its estimate based on what past history says is most likely.

Any scan tool is just a way to narrow down the possible causes. Someone still needs to look at the car and rule out the possibilities until the real cause is found. But al least here you get a little more than some incomprehensible code without context.

On the other hand, a green light from the CarMD is no bad thing...

1996 Lexus ES 300

This CarMD screen confirms there's nothing to worry about -- nothing related to a sensor connected to the ECU, in any case. I must say that's a reassuring bit of feedback when you're shopping for used cars.

What the CarMD can't do is predict the future, it can't tell me that the MAF sensor is going to go bad in 6 weeks. That would really be something.

Dan Edmunds, Director of Vehicle Testing

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