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Check engine light diagnostic

CMontoya79

Newb Le professional!
Joined
Dec 8, 2008
Messages
6,059
OK. Can a check engine light code change every time the car is plugged in to diagnostic equipment?

That’s the kind of bull I’m trying to be fed by a shop manager.

They said 2 bad 02 sensors, when the night before auto zone read bad evap solenoid vaccum stuck open rich.

They eventually fixed what my complaint was to begin with. I told them the part, they totally disregarded. Says different code and had to fix.

There is no reason why an 02 sensor should have gone bad on a properly maintained vehicle that is 6 years 61,000 miles.

Specifically, from one day to the next?

Your feedback is valued.
 
Time to use a different dealer and let the company know. Didn't you have issues with them before?
 
If AZ reset the codes, it's a possibility that something else set a code in the meantime.

It's also possible that AZ's device doesn't look as deep as the factory/shop's device.

If AZ did a KAM reset (keep alive memory) then it's possible the shop tech misinterpreted a not ready signal for a bad sensor. If they didn't know you had recently had the computer plugged into a scanner and possibly reset, this could cause the second set of eyes to give a false/bad diagnosis through no fault of their own.

Screenshot_20180202-142100.png
 
If AZ reset the codes, it's a possibility that something else set a code in the meantime.

It's also possible that AZ's device doesn't look as deep as the factory/shop's device.

If AZ did a KAM reset (keep alive memory) then it's possible the shop tech misinterpreted a not ready signal for a bad sensor. If they didn't know you had recently had the computer plugged into a scanner and possibly reset, this could cause the second set of eyes to give a false/bad diagnosis through no fault of their own.

View attachment 19549

@Scap
To my knowledge AZ didn’t reset anything, they only pulled code.

The shop would have to do further inspection and diagnostic to confirm a bad sensor, ie, voltage test, etc, right?

@tone-ny
This time I’m using a shop close to home that isn’t the dealer. Perhaps dealing with the dealer would have been better, as they KNOW, I don’t take BS.
 
@Scap
To my knowledge AZ didn’t reset anything, they only pulled code.

The shop would have to do further inspection and diagnostic to confirm a bad sensor, ie, voltage test, etc, right?

Well, 20 years ago I would have said yes.
Now, not so much. Too many parts changers anymore because no one knows how to troubleshoot.
 
Well, 20 years ago I would have said yes.
Now, not so much. Too many parts changers anymore because no one knows how to troubleshoot.
That’s just it. I’m not paying for an unnecessary part to be replaced if you didn’t check for it to be functioning properly.
 
That’s just it. I’m not paying for an unnecessary part to be replaced if you didn’t check for it to be functioning properly.

In their mind, that's how they fix it. Keep changing parts until it runs right.

Get yourself a Bluetooth OBD2 device and a phone app that will read the codes.

Most codes are able to be googled. Then you can browse vehicle specific forums for discussion and fixes.

That's how I troubleshoot my vehicles.
My truck started running like shit....the blowoff valve was wide open and dumping boost. I figured the blowoff died. Grabbed a CEL code, browsed a few forums, and read that a dirty MAP sensor could cause my issue.

Few squirts of cleaner on said sensor, and she's purring like an angry tiger again.
 
Also check if you can get the codes without an OBD2. On my truck, if I get a check engine light, I can turn my ignition on and off 3 time fast and the error code displays in the instrument panel (something like this - don't remember the exact sequence). Then I can google the code # to find the description.
 
I've been using the BlueDriver bluetooth scanner for a few years now, and I've only ever had one vehicle that it couldn't diagnose properly (a 2015 Toyota with instrument issues). Mine (and other similar scanners) will read the code, identify it for you, tell you common issues, and then common fixes -- as as a starting point. With many bluetooth scanners (and I'd have to imagine the high-end machines like the Star Scan and others that actual shops use), you can also look and see the last time codes were cleared, and what those codes were. Checking that is basic stuff in diagnosing a vehicle, to see if it's a problem that is recurring (or trying to be covered up).
 
I've been using the BlueDriver bluetooth scanner for a few years now, and I've only ever had one vehicle that it couldn't diagnose properly (a 2015 Toyota with instrument issues). Mine (and other similar scanners) will read the code, identify it for you, tell you common issues, and then common fixes -- as as a starting point. With many bluetooth scanners (and I'd have to imagine the high-end machines like the Star Scan and others that actual shops use), you can also look and see the last time codes were cleared, and what those codes were. Checking that is basic stuff in diagnosing a vehicle, to see if it's a problem that is recurring (or trying to be covered up).
Shop manager said he has a 15,000 diagnostic scanner. When I looked up prices for pro equipment 1-7 thousand.
 
Shop manager said he has a 15,000 diagnostic scanner. When I looked up prices for pro equipment 1-7 thousand.
Yeah, the pro stuff is ridiculously expensive (but necessary at shop levels). I thought about a Star Scan a few years ago when I really started getting by hands dirty on a regular basis, but at $1K... making use of my $89.00 BlueDriver and YouTube is good enough for me! :D
 
It's been my experience that very few technicians understand basic troubleshooting. This includes auto repair. My guess is about 1 in 10 or so.
 
Shop manager said he has a 15,000 diagnostic scanner. When I looked up prices for pro equipment 1-7 thousand.

Sounds like he bought a SnapOn....they should hb called StrapOn they way they screw people on their pricing.

Great tools, just not worth 10 times the price of everyone else's product.
 
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