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Unread 02-02-2012, 09:32 AM   #1
kbrown
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What does a dealership diagnostic machine/tool tell me?

Let me start by saying sorry if this is in the wrong section if it is feel free to move it, secondly i apologize if this has been covered a million times or once i couldnt find anything on google.

with that being said im fumbling with the idea of finally bringing my wj grand cherokee to the dealer paying them the fee of $85 and having them hook up their diagnostic machine/tool whatever you call it to my jeep and see if they can get more info about my check engine light than i can. i have one of the autozone readers so i get a cylinder 4 misfire detected which is also the same thing i get when i cycle the keep for the on board reader. so i guess my question is, will their machine/tool pick up something else or will i pay $85 to find out i have a cylinder 4 misfire?
will it detect low voltage somewhere, wire short, timing, and all of that sweet wonderful stuff i never know?
the $85 isnt a big deal im not trying to cheap out but this is free and if it saves me $85 ill be happy.

any further question about the jeep condition/what has been done to it see here: http://www.jeepforum.com/forum/f310/...-help-1301012/

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Unread 02-02-2012, 01:09 PM   #2
SnowdogMarc
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A dealers OBD2 reader can do live scans and run some tests on it which most of the ones you buy at AutoZone don't. But as far as it telling you to replace this wire and it's fixed...no it won't do that. Pick up a factory service manual and you can do just about any test and check they will do to find the problem.
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Unread 02-02-2012, 02:12 PM   #3
streetglideok
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The OE scan tools can read the codes, reflash the PCM as needed, as well as display live data readings from the sensors, fuel trims, misfires, etc, record the data, as well as allow it to perform a variety of tests. It wont tell anyone what to fix, or how to fix a vehicle, but it will give a slew of info to the technician, and allow them to find the problem. With just a misfire, it could be a matter of a bad coil, or spark plug, or something else. Scan tool wont always help with that, but the diagnostic time you are paying for should cover them to check the coil, etc. A popular misconception is, you bring it to me at work, I charge you $96, or whatever the going rate is in your area, and I hook up the scan tool, and presto I have the answer. Sadly, some mechanics think like that too. Reality is, it comes in, I hook up to it, and drive it, and watch the various readings. From there, depending on the problem, I do whatever tests are needed to find the problem. You can buy the factory service manual, and it will usually get you thru problems, but the factory test procedures are based on unaltered vehicles, in near new condition, and far from the reality of a car thats 5 years old or more. Lots of years of experience will teach you where you need to go with the problem at hand, and save time and money. GM is well known for "replace with known good part" for test procedures. Yeah, right,lol.
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Unread 02-02-2012, 02:26 PM   #4
streetglideok
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Here is an example of a car that came in just a few days ago, to show you what I mean. Audi A6 comes in, engine light flashing, runs poorly. Some mechanic(be afraid) said it probably needs cats. With the steep price of those babies for that car, the owner lets me verify the problem. Hook up to it, it has codes for misfires on each of six cylinders, and a multi cylinder misfire, as well as a cat efficiency code, and O2 sensor code. I drive it, and it runs horrible. I can see on the scan tool, its showing high misfire counts on cylinders 1 and 2, but no others at this time. Those two are side by side on bank 1. Knowing how bad the ignition coils are on VWs, I swap those two over to cylinders 4 and 5, and recheck. Misfires followed the coils. New plugs, as they were fouled, and new coils, it runs good. Go back and recheck the O2 sensor, its fine now that it doesnt have 2 dead holes blowing across it, and the cat, well, shes contaminated and lost function. Scan tool let me see which cylinders were misfiring live, see if the misfire moved when I swapped the coils, and with VW/Audi's, perform the O2 sensor and cat performance tests right there.
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Unread 02-02-2012, 05:26 PM   #5
Dickpalmer
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Autozone will read your codes for free if that's all you need.
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Unread 02-02-2012, 05:56 PM   #6
streetglideok
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Quote:
Originally Posted by Dickpalmer View Post
Autozone will read your codes for free if that's all you need.
He already owns, or has used a code reader, and pulled the codes thru the key cycle method. He's looking to learn what the difference would be in taking it to a shop vs using a code reader/sell more parts via shotgunning tool.
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Unread 02-03-2012, 06:14 AM   #7
zooby
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I love the Audi story. That is so typical at my work. You haven't lived until you get a customer who says "just plug that computer thing in and tell me whats wrong". Like steetglideok and snowdog said, reading codes only gives you an idea where to start.
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Unread 02-03-2012, 07:38 AM   #8
streetglideok
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Fords and autozone are another infamous couple. Fords setting P0171, and P0174 is real common, and every time, the zoneheads will con the customers into buying their junk bosch O2 sensors and injector cleaner. If it dont fix it, well it must be the ethanol in the gas of course. The scan tool wont come out and tell me whats wrong, but watching the fuel trims, when they go lean, and not go lean, I can quickly say, yeah its got a massive vacuum leak(pretty normal), or yeah, he is probably got a cold air intake and/or K&N filter and the MAF sensor is way off now. No code reader will ever tell you that kind of info. Here is an example right off my solus pro scanner:
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Unread 02-03-2012, 09:41 AM   #9
kbrown
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Thank you for the responses, I want under the impression it would give me step by step directions on how to fix it but based on what I'm seeing in the responses it will point me in the right direction. If I can find out if it is a fuel problem or a spark problem that's one step closer for me. Again thank you and I will head to a shop next week. Hopefully have this thing fixed and sold before tax season is over
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Unread 02-04-2012, 12:11 AM   #10
SnowdogMarc
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Having my own live scan tool and factory serv manual was a huge help in my engine swap. Was throwing codes for MAF and a few others having low voltage, Looking in the serv manual I discovered they all shared the same power feed wire. Took the harness apart and discovered I had a bad wire. replaced it and cleared the codes and everything was happy after that.
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Unread 02-05-2012, 12:05 AM   #11
kbrown
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My dads friends fiend owns a shop with one of these live scan machine things so $60 gets it read and he's trust worthy. Pretty great how convenient
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