Best way to use scanner during test drive

Question

So hopefully this weekend I’ll be checking out a used 04 Highlander v6 (100k) from a private party. I do have a “cheap” obd scanner and it does do live streaming data. Though the UI is kind of clunky and messy so I can’t live scan everything and be able to read it all. (Mostly because you can either select what you want to stream or stream all but it doesn’t give names for data, it just gives you placeholder values. So you’d have to click throw each thing just to see what each item is). Just wondering if you guys had suggestions of what was most important to scan live, that way I only have to deal with a handful of data. And secondary question if that’s cool, how many readiness items can fail/inc/na to pass an inspection? Does Inc always mean there’s been a reset or do certain things need to run for a second before completing? (Only ask because this scanner does not say when last clear was done).

scottykilmer · Accepted Answer

Well look at fuel trims short-term and long term that gives a really good idea of what's going on they shouldn't be a few percentages plus or minus from zero. And of course look for any codes

jack62 · Answer

Don't forget to cover the basics. Stick your finger in the tailpipe. Is it black and oily? If it is then its burning oil so walk away. Smell the exhaust for hints of coolant in the exhaust. Observe if it's smoking

The test drive is really important. Don't just take it for a spin around the block. Get it on the highway and see how it behaves at higher speeds as well. Feel for engine misses or any vibrations in the suspension/steering. Feel for transmission shifting/slipping issues.

For me, the most important thing right up there with transmission problems is Compression problems including head gasket leaks.

If they're not too bad yet you might not see them in the fuel trims but they're going to get worse, not better if they exist.

Most people selling a car aren't going to let you pull the spark plugs and do a compression test. (I wouldn't let buyers do that with a car I was selling either).

But you can do a relative compression test to give you an idea of the health of the engine. Maybe watch Scotty's video on how to do that. You'll have to invest a little bit of money (maybe $175 between the meter/scope and the amp clamp) but buying a car with a bad engine will cost a lot more.

You can check for combustion gasses in the coolant with a combustion leak test kit to see if there's a bad head gasket. (around $30). Scotty has a video on that too and a recommendation for a kit in the Tools link in the upper right of this page.

Investing around $200 so you don't buy a clunker is well worth the money.

https://youtu.be/RLOpo71JtIU?t=199

yaser · Answer

An important thing to keep in mind for this car is the service for the timing belt. Considering the age and mileage and being an interference engine, make sure it has been taken care of. If not, it can cost you a lot.