Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - can a code reader help in buying a used car?

olds455 · 03-24-2013, 09:15 PM

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.

03-24-2013, 09:15 PM	#4 (permalink)
olds455 EcoModding Lurker Join Date: Jun 2011 Location: Maryland Posts: 13 Century - '03 Buick Century 90 day: 35.41 mpg (US) Thanks: 6 Thanked 4 Times in 4 Posts	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.