BodybyFisher Posted December 29, 2005 Report Share Posted December 29, 2005 We have had a few members ask what they should look at when buying a new used car lately. While I know we all don't have Autotap, I thought this article that I received from Autotap was good information when buying a used car and another reason why I can't wait to buy Autotap, Mike Dear Michael, Here's a topic that's been brewing in the back of my mind for awhile now - How to use the OBDII system to buy a used car. First, a quick experience that I had. About a year ago we had another addition to the family that pushed us into minivan territory. That, and an occasional trailer-towing requirement, led us to shop for a late-model Chevy Astro van. There's a local used car lot that I've been happy with in the past. This low-overhead operation buys from overstocked dealerships and consistently sells close to wholesale prices. But, they have pretty much no history with any vehicles they get other than driving them home and washing them. After taking the van for a drive, things seemed pretty good. So, I took it home for the night on loan so I could crawl under and around it, as well as spend some time with AutoTap. Everyone has their own routine for "kicking the tires" so I'll skip right to what I was looking for with AutoTap. Any scantool will give you some of this info, but in my experience you'll need either AutoTap or access to a shop-level tool to get this much detail. Miles Since Code Clear - this told me exactly how many miles since someone either disconnected the battery or used a scantool to clear the Check Engine Light. I've had a number of emails from people that have worked in used-car lots. From their reports many used car lots are more likely to clear the Check Engine light than actually fix the problem. Long Term Fuel Trim (both banks) - remember a few weeks ago when I said the O2 sensors provide the feedback for the computer to fine-tune the air/fuel mixture? This reading tells you exactly what "correction factor" is being applied. If this hits +/- 25% a code will be set. In my experience, it's usually less than 10% If you see numbers over 10% I'd be suspicious that something is either out of whack, or on its way out. Note - don't worry so much about this number at idle, check it during normal driving conditions. Knock Retard (different vehicle makes have different names for this one) - check this with the engine fully warm, under a good load, usually at lower RPM - like lugging up a hill on a highway. The engine's knock sensor detects "pinging" long before your ears and retards the timing to compensate. That's a great feature, but it masks the problem from the driver. As long as the car's burning the recommended octane fuel you shouldn't see knock retard. I wouldn't be concerned about a little activity, but consistent knock is the sign of trouble and could lead to larger problems. Pending DTC's - remember, it often takes a couple driving cycles of trouble for the Check Engine light to turn on. But - the computer knows they're there and AutoTap can show them to you. This is most common when the "Miles Since Code Clear" reading is very low - it definitely indicates that someone has cleared a code without fixing the problem. Odometer - AutoTap will show the mileage on some vehicles - be sure it's a close match with the reading on the dash. We've had at least one AutoTap owner return a used car when the dealer couldn't explain the discrepancy. Misfires - Remember the OBDII system is pretty effective at detecting misfires. With AutoTap you can see misfires that are below the threshold of turning on the Check Engine light - but might just be an indicator of a pending problem. Be particularly concerned if one cylinder shows considerably more misfires than another. Those are all the items I can think of for now. Remember, if you're not sure what's "normal" for any readings you see, just plug into another car with the same engine and compare the readings. And, once you buy your new-used vehicle, be sure and use your scantool to log some "baseline" data (AutoTap's logging feature is great for this, most tools will require a pencil and paper). Those baseline logfiles will be a huge help if you have any trouble down the road. If you see anything funny, start by showing it to the dealer and see what they say - if you feel like a bit of retribution, show them your AutoTap tell them how little you paid for it! I've found most to be pretty open about known issues - if they get defensive you're probably better off going elsewhere. Happy Repairs, Mike Fahrion www.autotap.com P.S. Back to our Astro Van - I actually found a pending code and suspiciously low mileage since code clear. So, the dealer wrote me a full year warranty for that particular problem in case it should rear it's ugly head. 20,000 miles later all is well. Copyright 2004 B&B Electronics Manufacturing Co. Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 31, 2005 Author Report Share Posted December 31, 2005 You know, I have noticed that when I post these Autotap "tech papers", they generate very little discussion. Personally, I think they are very informative and helpful in understanding how the system functions and reacts. I have learned a lot about how engine management systems work and how useful tools such as this can enhance our diagnostic skills. This Autotap article for me illicits a BIT WOW.... 1) Am I just an odd SOB, that likes this stuff, and this is not a BIG WOW to anyone else? 2) is this considered OT and no one wants to post to it? and I am being treated as a TROLL? If no one finds this stuff interesting and helpful, I can stop posting it and just put it in a folder on my hard drive. What do you guys think of this program. I can hear a PIN drop in this thread. Matt, did give off a BIG wow on another Autotap reference. You guys out there with laptops, this is a very cheap solution that to ME.... would be the BEST TOOL you ever buy, we will be able to diagnose ANY OBD2 system...... I have been prowling Compusa looking at laptops for weeks WTF do you guys think.... No WOW's out there besides me? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
chazglenn3 Posted December 31, 2005 Report Share Posted December 31, 2005 I think it is cool...but I am a cheap S.O.B. and don't want to spend the $300 on the unit. I did go and read the information on the website! Charles Charles Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 31, 2005 Author Report Share Posted December 31, 2005 I think it is cool...but I am a cheap S.O.B. and don't want to spend the $300 on the unit. I did go and read the information on the website! Charles When I get it and start doing amazing things with it, I'll bet you change your mind about the price.... I am sure that I will save myself $300 with it in the first few weeks.... I have a LIST of things that are NOT working correctly, for instance my Twilight Sentinel. I'll bet that I will be able to see real time information on that system... It NAILS AC systems Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
KHE Posted December 31, 2005 Report Share Posted December 31, 2005 I think it is cool...but I am a cheap S.O.B. and don't want to spend the $300 on the unit. I did go and read the information on the website! Charles When I get it and start doing amazing things with it, I'll bet you change your mind about the price.... I am sure that I will save myself $300 with it in the first few weeks.... I have a LIST of things that are NOT working correctly, for instance my Twilight Sentinel. I'll bet that I will be able to see real time information on that system... It NAILS AC systems Don't assume that a lack of responses/posts euuates to a lack of interest in the Autotap posts. I think they are very informative even though I don't post any responses. If your Twilight Sentinel is acting up - as in not turning on or off the headlights soon enough, it is most likely the photocell in the dash. They drift in calibration over time and a new one is $25 and will cure the problem. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
chazglenn3 Posted December 31, 2005 Report Share Posted December 31, 2005 I had that problem with my 1996 STS also...new sensor from the dealer and all was well. Charles Charles Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 31, 2005 Author Report Share Posted December 31, 2005 Kevin, I was kind of tongue in cheek busting the board's chops on this, this Autotap program is amazing to me, I am surprised others have not shown as much interest in it. Thanks regarding the twilight sentinal. Let me try to explain what is happening. During the day, sometimes when I try to 'flash' someone, I have noticed that my high beams come on and stay on, meaning that my headlights are commanded on in bright sunlight, when they should not be.. I should just be able to 'flash' on and off with no high beam lock in.. I hope that is a clear enough explanation. So something is causing my lights to come on when they should not, will that sensor do that? I have the reverse of what you are saying, the lights not turning on.... Thanks, Mike Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
JimD Posted December 31, 2005 Report Share Posted December 31, 2005 You know, I have noticed that when I post these Autotap "tech papers", they generate very little discussion. Personally, I think they are very informative and helpful in understanding how the system functions and reacts. I have learned a lot about how engine management systems work and how useful tools such as this can enhance our diagnostic skills.... WTF do you guys think.... No WOW's out there besides me? At the risk of repeating myself, I have been using this interface box for more than 4 years and I love it for "P" codes and the ability to run a log file under street driving conditions. It is limited to "P" codes, but the price was right for me at the time (when I had vehicles other than a Cadillac). I looked at Autotap and could not rationalize the price difference. http://obddiagnostics.com/ Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 31, 2005 Author Report Share Posted December 31, 2005 Interesting Jim, they even have software for my Pocket PC, thanks for repeating yourself! Mike Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
epricedright Posted December 31, 2005 Report Share Posted December 31, 2005 I'd be interested in Autotap, but since it apparently doesn't work for "antiques", I'll have to wait. One day though... Link to comment Share on other sites More sharing options...
KHE Posted December 31, 2005 Report Share Posted December 31, 2005 Kevin, I was kind of tongue in cheek busting the board's chops on this, this Autotap program is amazing to me, I am surprised others have not shown as much interest in it. Thanks regarding the twilight sentinal. Let me try to explain what is happening. During the day, sometimes when I try to 'flash' someone, I have noticed that my high beams come on and stay on, meaning that my headlights are commanded on in bright sunlight, when they should not be.. I should just be able to 'flash' on and off with no high beam lock in.. I hope that is a clear enough explanation. So something is causing my lights to come on when they should not, will that sensor do that? I have the reverse of what you are saying, the lights not turning on.... Thanks, Mike It sould still be the sensor - it is the sensor that is a flat disc in the dash grille - next to the spherical ball sun load sensor. Photocells drift in calibration over time and that may be the case here. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 31, 2005 Author Report Share Posted December 31, 2005 Thanks Kevin, I'll check it out, Mike Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
cdictas Posted December 31, 2005 Report Share Posted December 31, 2005 Mike, Like the other members on the board, I took a quick look at autotap's website. They listed a whole host of items that they can detect. What I didn't see was the ability to reprogram key fabs. On 1998 and up vehicles you need a tech 2 to reprogram. It would been great if someone on the board who has used both pieces of software could give some pros and cons between the two. In other words, is this the second best software package to GM's tech 2? Chuck Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 31, 2005 Author Report Share Posted December 31, 2005 I am finding that there are a whole bunch of possibilities, I have a DELL X5, so this product interests me also, http://tools.baumtools.com/ottodiagnostic.jsp See this also, it has bi-directional control http://tools.baumtools.com/ottoscanturbo_gm.jsp How about a oscilloscope on an X5! http://tools.baumtools.com/ottoscopeturbo.jsp What I like about the autotap is their newsletter that has opened my eyes up to a new level of diagnostics and made me realize that I need to get something on this level... Mike (right now the Dell X5 is a glorified address book for me with 2,000 business addresses and it gives me the ability to play FREECELL so this diagnostic software looks VERY cool!!!) Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
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