Pending Trouble Code Reader Question

I just bought a CAN OBDII trouble code reader along with a CD containing 7000 codes including brand specific codes. How useful would a pending trouble code reader be for home use?

So far I haven’t needed to use mine on any of my vehicles but I have checked codes for some friends.

What is a “pending trouble code reader”?

i had NO idea that OBDII was updated to not just tell of codes thrown, but of potential codes which are about to be thrown.

upon reflection, i am not sure it is important either way, since most codes aren’t life threatening, but i guess since you bought it, you will probably have less actual codes (as long as you use it once in a while.)

i use mine about three or four times a year, either on one of my cars, or on friends. since i have one, and my friends know about it it does get used. i am glad that mine doesn’t have the “pending” ability, because one of my friends would probably be over every week (he is sorta a car hypochondriac.)

A pending trouble code occurs during one drive cycle. If it doesn’t occur during any proceeding drive cycles it remains a pending trouble code. If the code occurs again during a proceeding drive cycle it becomes a mature code, and the Check Engine light comes on.


A pending code reader would be practically useless. The reason the engineer’s added this step was to filter out gremlins that happen with sophisticated systems. In other words, a ‘one time has no case’ filter. If it happens again within so many cycles, then it will determine there is a problem, and post the code.

Thanks for the replies and interest. It’s not the one that I bought but an Innova 3030 for about $70 at a local discount farm supply store here can read pending codes. Web site is

I’d have to say it’s all pretty useless if you’re not a knowledgable technician that knows what codes mean… One example I deal with sometimes at my shop is the dreaded code P0420. This code says catalytic convertor efficiency below threshhold. 9 times out of 10 you need a convertor, so if your inexperience leads you to replace a $1000 cat, you PROBABLY did right. BUT, the rear oxygen sensor after the cat is used to monitor the cat, and a bad or defective rear sensor can’t monitor the cat. So it sets P0420. Maybe the light is going to come back on cause you really needed a $150 oxygen sensor instead… I’m just saying to be careful how you use it. It CAN cost you a whole lot more money than paying someone qualified to check it out for you…