can a code reader help in buying a used car?

[kalifornia]

Im planning on buying a used car soon. Can an ultra gauge (preferebly) or similiar obII reader determine if any codes have ever been sent, vehicle history so to speak? I would hate to buy a car with a problem that a code reader could easily alert me to. Any tips on buying a used car and error codes would be most appreciated. thanks friends!

[Smurf]

UltraGauge does display CEL codes, you have to Google what the code means.

[Ryland]

It will only show stored codes, not codes that have been reset, it will allow you to see what the engine is doing of course, how fast it is warming up and going in to closed loop, battery voltage and all that other info, including gas mileage! I always take mine along when looking at used cars, I bought a OBDII book that lists off all of the engine codes and common problems that go with them.

[olds455]

My scan tool only shows whether the car has not had enough time to see and evaluate every system after any codes have been reset.

It will indicate with a yellow light that codes(s) were just reset and the car has not had enough time to evaluate all systems for good or bad function. The CEL won't be on, but the tool will show a yellow light that says that codes were recently reset. I have an Equus 3140. If the toll read a car with active codes, it will give you a red light and the codes. If the car has had enough time to evaluate itself, it gives me a green light.

I don't know a way to get historical info with the tools I have. I have never tried to use the UG for code reading. I have noticed that it will indicate a code is pending before the CEL comes on. I have not looked to see if it will tell me what code(s) is (are) pending though.

General idea for used car inspection:

It runs and drives well. Smooth at idle, while driving and shifts well.
Watch temps and oil pressure while on the test drive.

I prefer to test a car when it has been sitting overnight and is not already warmed up. A warm engine will mask some problems. On the flip side, make sure you run and drive it long enough for everything to warm completely to evaluate behavior when warm. Shut down and restart both cold and warm

I'm keen on looking for body damage that was poorly repaired. Look for seams where panels would have been replaced to be sure they are right. I saw a Neon recently that looked good on the outside with some small signs of a repaint. However the trunk linin was wet that pointed me to a bad qtr panel repair that leaked from the wheel well A Lot.

I always look under the oil fill cap and give it sniff. Bad, nasty oil has a distinct, gross smell that will linger after a "fresh" oil change that makes the dip stick oil look good.

I also look at the coolant to check color and cleanliness. A cold car is needed for this one. Check the overflow jug and the radiator if possible, not all cars let you see into the radiator.

Funny tire wear patterns are indication of bad alignment, damage or worn parts. BRAND NEW tires can be a hint of the same problems. (Brand new tires are not always good for that reason) They can easily hide the problems above.

Make sure EVERY accessory works or doesn't. Defroster, heat, AC, radio: presets CD, Aux, Reception.....EVERYTHING! Check the things you don't need to use this season. It is easy to forget something.

Note the dash lights with the key in the ON position with the engine not running. Sneaky people have been known to remove light bulbs for problem indicators. ABS, Airbag and CEL bulbs are easy to remove and lead you to believe the systems are 100% good, when they are really 100% BROKEN.

.....I'm a skeptic at best with used cars and I typically stay away from dealers only based on the purchase prices. Private parties have the less expensive cars available; dealer markup is how they make money. But I like my money too.

Best advice after the above is to remember there are more cars out there; you don't need to buy the one in front of you. The last one I bought took 1.5 months and probably 10 cars before I found the right one....and it still had a hidden airbag problem that showed itself only after I got it home. (I got to learn how to fix airbags though)


Yikes, I wrote a book. There is More to it than I thought before I started writing.

[allenh318]

If you have a code scanner, you can check a lot of engine components quickly. Engine temp and thermostat working, open/closed loop, oxygen sensor working, along with any codes stored. it can be very helpful determining whether or not more money will have to be put into it. Plus the seller may decide to tell you any problems he has since he knows you are a smart buyer.

[kamesama980]

In just the right situation maybe. 99% of the time, no. Depends on the scanner and what's wrong with the car.

Simply knowing the code isn't hard, just stop by autozone on the test drive and have them scan it.

No scanner can find a code that's been cleared. If the battery cables are removed or the codes are cleared, it's all gone. If the battery goes flat sitting on the lot, codes are gone. It cannot tell you the "history" of the car.

All the really useful data (fuel trims, live data, etc) won't be accessible unless you have a moderately expensive scanner...$200+ for a basic handheld one.

99% of the time, you won't find anything conclusive. Even if you do notice something like the fuel trims being high you can't do much about it since it isn't your car. you *may* be able to get some negotiation room but it's doubtful it'll offset the cost of a scanner to get fuel trims. The seller also might just give you the finger.