nothermark

It would be nice to have a link or two to sites that explain moderrn
code reader diagnosis techniques. Does anybody have any favorites?

Mike Marlow

On 13 Jan 2009 06:32:01 -0600, nothermark cast forth these pearls of
wisdom...:

> It would be nice to have a link or two to sites that explain moderrn
> code reader diagnosis techniques. Does anybody have any favorites?

What do you mean by code reader techniques? Ya plugs it in and ya reads
what it says.

--

-Mike-
mmarlowREMOVE@alltel.net

Voyager

Mike Marlow wrote:
> On 13 Jan 2009 06:32:01 -0600, nothermark cast forth these pearls of
> wisdom...:
>
>> It would be nice to have a link or two to sites that explain moderrn
>> code reader diagnosis techniques. Does anybody have any favorites?
>
> What do you mean by code reader techniques? Ya plugs it in and ya reads
> what it says.
>

Yes, but I know at least one Autozone that can't handle that...

nothermark

On Tue, 13 Jan 2009 22:50:00 -0500, Mike Marlow
<mmarlowREMOVE@alltel.net> wrote:

>On 13 Jan 2009 06:32:01 -0600, nothermark cast forth these pearls of
>wisdom...:
>
>> It would be nice to have a link or two to sites that explain moderrn
>> code reader diagnosis techniques. Does anybody have any favorites?
>
>What do you mean by code reader techniques? Ya plugs it in and ya reads
>what it says.

But if it has a couple codes what do you do?

Do the codes go away once you fixed the problem or do you have to do
something to clear them?

That kind of stuff. Basic troubleshooting on a modern vehicle with a
code reader available as oppsed to how we troubleshot our 57 Chevy.

hyundaimech@gmail.com

On Jan 14, 9:12 pm, nothermark <notherm...@not.here> wrote:
> On Tue, 13 Jan 2009 22:50:00 -0500, Mike Marlow
>
> <mmarlowREM...@alltel.net> wrote:
> >On 13 Jan 2009 06:32:01 -0600, nothermark cast forth these pearls of
> >wisdom...:
>
> >> It would be nice to have a link or two to sites that explain moderrn
> >> code reader diagnosis techniques. Does anybody have any favorites?
>
> >What do you mean by code reader techniques? Ya plugs it in and ya reads
> >what it says.
>
> But if it has a couple codes what do you do?
>
> Do the codes go away once you fixed the problem or do you have to do
> something to clear them?
>
> That kind of stuff. Basic troubleshooting on a modern vehicle with a
> code reader available as oppsed to how we troubleshot our 57 Chevy.

There's little necessary to operate a code reader. It simply spits
out the codes which indicate something about what the computer has
seen that it didn't like. The next step after that is to decipher
what that code means. There are a few websites that will give
information on the codes. I simply googled "OBD-II codes" and
received a few nice hits on the first page.

Further diagnosis is where things get complicated. Even for universal
codes (P0xxx), there can be different criteria for setting that code
on different vehicles. To get this information, you'll need access to
a shop manual for the vehicle in question. An accurate diagnosis will
often require knowing the conidtions that must be met for the code to
set. The technician will, in most cases, make readings with a scan
tool, helping him conclude what is occurring with the car. In some
cases, equally valid tests can be made with a VOM, but other cases
require using data interpreted by the vehicle's computer.

Here's an example of a diagnosis/repair I made today:
Car arrives -- check engine lamp on -- owner states only minor change
in performance.
Read codes. P0455, P1166 (unable to properly compensate air-fuel
ratio, bank 1), P1167 (unable to properly compensate air-fuel ratio,
bank 2)
Read freeze frame data (conditions present when code set). Freeze
frame data indicate conditions when P0455 set. Notice short term and
long term fuel trims* very high positive both banks.
Clear codes. Check fuel cap. Run evaporative self-test. Test
passes. Conclude fuel cap was left loose or off, causing P0455, then
later installed correctly.
Check current data and verify both fuel trim values still high.
Check air flow readings. Find readings low compared to known good
readings.
Check PCV valve, brake booster, piping/hose between intake and purge
valve, fuel pressure regulator hose for vacuum leaks. All okay. Find
idle actuator gasket out of position and leaking air into engine.
Reposition gasket and recheck data. Fuel trims now normal.

*Fuel trim represents the adjustment the computer makes to the
injector on-time in comparison to what the computer would expect based
on air flow readings, throttle position, engine rpm, and other
factors. Positive numbers mean the injectors are being kept on
longer. Negative numbers mean the injector on-time is being adjusted
smaller.

This diagnosis is a good example of the ability to use a scan tool to
help in diagnosis. A do-it-yourselfer would never have been able to
run the evap. test. And although a do-it-yourselfer wouild have been
able to check all the things I checked for P1166 and P1167, using the
scan tool provides for near-instant feedback of results. I can check
for leaks by pinching off a vacuum hose and watching the fuel trim
numbers. If pinching the hose stops a leak, the fuel trim numbers
will come down.

This diagnosis is also a good example of how to use logic. Oxygen
sensors are the single most frequent cause of P1166 and P1167 codes on
the vehicle on which I was working. In this case, however, they
weren't the primary suspect. Why? Because I have a near-identical
problem on both banks, and it would be highly unlikely for the sensors
on both banks to fail simultaneously and in the same manner. Also
note that it's improper to conclude that because the air flow readings
are low that the air flow sensor is defective. In this case, the
readings were low but accurate. The high fuel trim values were due to
the computer needing to compensate for the additional are leaking into
the engine that wasn't being measured by the sensor. Low fuel
pressure could have also been the culprit, but that would have been
much more likely to cause a significant power loss at high load/high
rpm and result in a significant complaint about performance. If the
air flow readings been correct, checking the fuel pressure would have
probably been the next step.

Mike Marlow

On 14 Jan 2009 20:12:01 -0600, nothermark cast forth these pearls of
wisdom...:

> On Tue, 13 Jan 2009 22:50:00 -0500, Mike Marlow
> <mmarlowREMOVE@alltel.net> wrote:
>
>>On 13 Jan 2009 06:32:01 -0600, nothermark cast forth these pearls of
>>wisdom...:
>>
>>> It would be nice to have a link or two to sites that explain moderrn
>>> code reader diagnosis techniques. Does anybody have any favorites?
>>
>>What do you mean by code reader techniques? Ya plugs it in and ya reads
>>what it says.
>
> But if it has a couple codes what do you do?
>
> Do the codes go away once you fixed the problem or do you have to do
> something to clear them?
>
> That kind of stuff. Basic troubleshooting on a modern vehicle with a
> code reader available as oppsed to how we troubleshot our 57 Chevy.

Can't boil it down to that level of simplicity. Too many computers and too
many inter-related systems today. Just like that 57 Chevy, it requires a
certain level of familiarity and experience with the vehicles to wind your
way through such things as multiple codes. The 57 was capable of showing
you multiple and confusing symptoms - today's cars just raise that to a new
level.

--

-Mike-
mmarlowREMOVE@alltel.net

Ed Pawlowski

"Mike Marlow" <mmarlowREMOVE@alltel.net> wrote in message
> Can't boil it down to that level of simplicity. Too many computers and
> too
> many inter-related systems today. Just like that 57 Chevy, it requires a
> certain level of familiarity and experience with the vehicles to wind your
> way through such things as multiple codes. The 57 was capable of showing
> you multiple and confusing symptoms - today's cars just raise that to a
> new
> level.
>
> --
>
> -Mike-
> mmarlowREMOVE@alltel.net

So, it really is rocket surgery.

Mike Marlow

On Wed, 14 Jan 2009 22:06:31 -0500, Ed Pawlowski cast forth these pearls of
wisdom...:

> "Mike Marlow" <mmarlowREMOVE@alltel.net> wrote in message
>> Can't boil it down to that level of simplicity. Too many computers and
>> too
>> many inter-related systems today. Just like that 57 Chevy, it requires a
>> certain level of familiarity and experience with the vehicles to wind your
>> way through such things as multiple codes. The 57 was capable of showing
>> you multiple and confusing symptoms - today's cars just raise that to a
>> new
>> level.
>>
>> --
>>
>> -Mike-
>> mmarlowREMOVE@alltel.net
>
> So, it really is rocket surgery.

With a little smoke, mirrors and lights thrown in.

--

-Mike-
mmarlowREMOVE@alltel.net

nothermark

On Wed, 14 Jan 2009 18:53:34 -0800 (PST), hyundaimech@gmail.com wrote:

>On Jan 14, 9:12 pm, nothermark <notherm...@not.here> wrote:
>> On Tue, 13 Jan 2009 22:50:00 -0500, Mike Marlow
>>
>> <mmarlowREM...@alltel.net> wrote:
>> >On 13 Jan 2009 06:32:01 -0600, nothermark cast forth these pearls of
>> >wisdom...:
>>
>> >> It would be nice to have a link or two to sites that explain moderrn
>> >> code reader diagnosis techniques. Does anybody have any favorites?
>>
>> >What do you mean by code reader techniques? Ya plugs it in and ya reads
>> >what it says.
>>
>> But if it has a couple codes what do you do?
>>
>> Do the codes go away once you fixed the problem or do you have to do
>> something to clear them?
>>
>> That kind of stuff. Basic troubleshooting on a modern vehicle with a
>> code reader available as oppsed to how we troubleshot our 57 Chevy.
>
>There's little necessary to operate a code reader. It simply spits
>out the codes which indicate something about what the computer has
>seen that it didn't like. The next step after that is to decipher
>what that code means. There are a few websites that will give
>information on the codes. I simply googled "OBD-II codes" and
>received a few nice hits on the first page.
>
>Further diagnosis is where things get complicated. Even for universal
>codes (P0xxx), there can be different criteria for setting that code
>on different vehicles. To get this information, you'll need access to
>a shop manual for the vehicle in question. An accurate diagnosis will
>often require knowing the conidtions that must be met for the code to
>set. The technician will, in most cases, make readings with a scan
>tool, helping him conclude what is occurring with the car. In some
>cases, equally valid tests can be made with a VOM, but other cases
>require using data interpreted by the vehicle's computer.
>
>Here's an example of a diagnosis/repair I made today:
>Car arrives -- check engine lamp on -- owner states only minor change
>in performance.
>Read codes. P0455, P1166 (unable to properly compensate air-fuel
>ratio, bank 1), P1167 (unable to properly compensate air-fuel ratio,
>bank 2)
>Read freeze frame data (conditions present when code set). Freeze
>frame data indicate conditions when P0455 set. Notice short term and
>long term fuel trims* very high positive both banks.
>Clear codes. Check fuel cap. Run evaporative self-test. Test
>passes. Conclude fuel cap was left loose or off, causing P0455, then
>later installed correctly.
>Check current data and verify both fuel trim values still high.
>Check air flow readings. Find readings low compared to known good
>readings.
>Check PCV valve, brake booster, piping/hose between intake and purge
>valve, fuel pressure regulator hose for vacuum leaks. All okay. Find
>idle actuator gasket out of position and leaking air into engine.
>Reposition gasket and recheck data. Fuel trims now normal.
>
>*Fuel trim represents the adjustment the computer makes to the
>injector on-time in comparison to what the computer would expect based
>on air flow readings, throttle position, engine rpm, and other
>factors. Positive numbers mean the injectors are being kept on
>longer. Negative numbers mean the injector on-time is being adjusted
>smaller.
>
>This diagnosis is a good example of the ability to use a scan tool to
>help in diagnosis. A do-it-yourselfer would never have been able to
>run the evap. test. And although a do-it-yourselfer wouild have been
>able to check all the things I checked for P1166 and P1167, using the
>scan tool provides for near-instant feedback of results. I can check
>for leaks by pinching off a vacuum hose and watching the fuel trim
>numbers. If pinching the hose stops a leak, the fuel trim numbers
>will come down.
>
>This diagnosis is also a good example of how to use logic. Oxygen
>sensors are the single most frequent cause of P1166 and P1167 codes on
>the vehicle on which I was working. In this case, however, they
>weren't the primary suspect. Why? Because I have a near-identical
>problem on both banks, and it would be highly unlikely for the sensors
>on both banks to fail simultaneously and in the same manner. Also
>note that it's improper to conclude that because the air flow readings
>are low that the air flow sensor is defective. In this case, the
>readings were low but accurate. The high fuel trim values were due to
>the computer needing to compensate for the additional are leaking into
>the engine that wasn't being measured by the sensor. Low fuel
>pressure could have also been the culprit, but that would have been
>much more likely to cause a significant power loss at high load/high
>rpm and result in a significant complaint about performance. If the
>air flow readings been correct, checking the fuel pressure would have
>probably been the next step.

Sorry for not getting back faster. Almost too much OT.

Thanks for the explanation. This is what I was looking for. It seems
that the only place for the symptom tree is the specific service
manual?

Philosphically I was looking for a web site or suggested source that
had decision tree's and explanations for how to run this kind of
diagnostic procedure. It was my thought that it would be both a help
for us self maintainers and a place to send the whiners too when they
wonder why it took so long to "fix a simple problem".

631grant

Wow, I'm impressed!!!! How about moving to Athens, Ga???? and the
dealership there?


<hyundaimech@gmail.com> wrote in message
news:f5810fc0-4ba7-47ea-99a8-8dad122ef500@b1g2000yqg.googlegroups.com...
On Jan 14, 9:12 pm, nothermark <notherm...@not.here> wrote:
> On Tue, 13 Jan 2009 22:50:00 -0500, Mike Marlow
>
> <mmarlowREM...@alltel.net> wrote:
> >On 13 Jan 2009 06:32:01 -0600, nothermark cast forth these pearls of
> >wisdom...:
>
> >> It would be nice to have a link or two to sites that explain moderrn
> >> code reader diagnosis techniques. Does anybody have any favorites?
>
> >What do you mean by code reader techniques? Ya plugs it in and ya reads
> >what it says.
>
> But if it has a couple codes what do you do?
>
> Do the codes go away once you fixed the problem or do you have to do
> something to clear them?
>
> That kind of stuff. Basic troubleshooting on a modern vehicle with a
> code reader available as oppsed to how we troubleshot our 57 Chevy.

There's little necessary to operate a code reader. It simply spits
out the codes which indicate something about what the computer has
seen that it didn't like. The next step after that is to decipher
what that code means. There are a few websites that will give
information on the codes. I simply googled "OBD-II codes" and
received a few nice hits on the first page.

Further diagnosis is where things get complicated. Even for universal
codes (P0xxx), there can be different criteria for setting that code
on different vehicles. To get this information, you'll need access to
a shop manual for the vehicle in question. An accurate diagnosis will
often require knowing the conidtions that must be met for the code to
set. The technician will, in most cases, make readings with a scan
tool, helping him conclude what is occurring with the car. In some
cases, equally valid tests can be made with a VOM, but other cases
require using data interpreted by the vehicle's computer.

Here's an example of a diagnosis/repair I made today:
Car arrives -- check engine lamp on -- owner states only minor change
in performance.
Read codes. P0455, P1166 (unable to properly compensate air-fuel
ratio, bank 1), P1167 (unable to properly compensate air-fuel ratio,
bank 2)
Read freeze frame data (conditions present when code set). Freeze
frame data indicate conditions when P0455 set. Notice short term and
long term fuel trims* very high positive both banks.
Clear codes. Check fuel cap. Run evaporative self-test. Test
passes. Conclude fuel cap was left loose or off, causing P0455, then
later installed correctly.
Check current data and verify both fuel trim values still high.
Check air flow readings. Find readings low compared to known good
readings.
Check PCV valve, brake booster, piping/hose between intake and purge
valve, fuel pressure regulator hose for vacuum leaks. All okay. Find
idle actuator gasket out of position and leaking air into engine.
Reposition gasket and recheck data. Fuel trims now normal.

*Fuel trim represents the adjustment the computer makes to the
injector on-time in comparison to what the computer would expect based
on air flow readings, throttle position, engine rpm, and other
factors. Positive numbers mean the injectors are being kept on
longer. Negative numbers mean the injector on-time is being adjusted
smaller.

This diagnosis is a good example of the ability to use a scan tool to
help in diagnosis. A do-it-yourselfer would never have been able to
run the evap. test. And although a do-it-yourselfer wouild have been
able to check all the things I checked for P1166 and P1167, using the
scan tool provides for near-instant feedback of results. I can check
for leaks by pinching off a vacuum hose and watching the fuel trim
numbers. If pinching the hose stops a leak, the fuel trim numbers
will come down.

This diagnosis is also a good example of how to use logic. Oxygen
sensors are the single most frequent cause of P1166 and P1167 codes on
the vehicle on which I was working. In this case, however, they
weren't the primary suspect. Why? Because I have a near-identical
problem on both banks, and it would be highly unlikely for the sensors
on both banks to fail simultaneously and in the same manner. Also
note that it's improper to conclude that because the air flow readings
are low that the air flow sensor is defective. In this case, the
readings were low but accurate. The high fuel trim values were due to
the computer needing to compensate for the additional are leaking into
the engine that wasn't being measured by the sensor. Low fuel
pressure could have also been the culprit, but that would have been
much more likely to cause a significant power loss at high load/high
rpm and result in a significant complaint about performance. If the
air flow readings been correct, checking the fuel pressure would have
probably been the next step.

631grant

I would give YOUR left nut, Mike, for the simplicity of the 57 Chevy that I
once had! )
Decision tree:
Spark or no spark?
Fuel or no fuel?
Check points and dwell as well as timing.
Check carb jets and float level.
Battery voltage and starter.

Hmmm, now where is that darn computer? What's a computer???

End of tree.


"Mike Marlow" <mmarlowREMOVE@alltel.net> wrote in message
news:10pysyzdx8v8w$.180p1mvx5dtew.dlg@40tude.net.. .
> On 14 Jan 2009 20:12:01 -0600, nothermark cast forth these pearls of
> wisdom...:
>
>> On Tue, 13 Jan 2009 22:50:00 -0500, Mike Marlow
>> <mmarlowREMOVE@alltel.net> wrote:
>>
>>>On 13 Jan 2009 06:32:01 -0600, nothermark cast forth these pearls of
>>>wisdom...:
>>>
>>>> It would be nice to have a link or two to sites that explain moderrn
>>>> code reader diagnosis techniques. Does anybody have any favorites?
>>>
>>>What do you mean by code reader techniques? Ya plugs it in and ya reads
>>>what it says.
>>
>> But if it has a couple codes what do you do?
>>
>> Do the codes go away once you fixed the problem or do you have to do
>> something to clear them?
>>
>> That kind of stuff. Basic troubleshooting on a modern vehicle with a
>> code reader available as oppsed to how we troubleshot our 57 Chevy.
>
> Can't boil it down to that level of simplicity. Too many computers and
> too
> many inter-related systems today. Just like that 57 Chevy, it requires a
> certain level of familiarity and experience with the vehicles to wind your
> way through such things as multiple codes. The 57 was capable of showing
> you multiple and confusing symptoms - today's cars just raise that to a
> new
> level.
>
> --
>
> -Mike-
> mmarlowREMOVE@alltel.net

Mike Marlow

On Tue, 27 Jan 2009 23:28:24 -0500, 631grant cast forth these pearls of
wisdom...:

> I would give YOUR left nut, Mike, for the simplicity of the 57 Chevy that I
> once had! )
> Decision tree:
> Spark or no spark?
> Fuel or no fuel?
> Check points and dwell as well as timing.
> Check carb jets and float level.
> Battery voltage and starter.
>
> Hmmm, now where is that darn computer? What's a computer???
>

You sir, better be careful where you're passing out my left nut - or my
right nut for that matter. Was just trying to say that even the old cars,
as simple as they were compared to today's computerized cars, had their own
ability to symie. Intermittent problems, conflicting symptoms, quirky
designs, etc.



--

-Mike-
mmarlowREMOVE@alltel.net

CBX2@webtv.net

Mike Marlow wrote:

>
> You sir, better be careful where you're passing out my left nut - or my
> right nut for that matter. Intermittent problems, conflicting symptoms, quirky
> designs, etc.

Why do all the topics of late center around my old lady?

631grant

Yea, you're right, of course. Just poking fun. But you have to admit, it
was sooooo much easier then.


"Mike Marlow" <mmarlowREMOVE@alltel.net> wrote in message
news:3l1wb5q4kvb1.11mdfpj1bmmg6$.dlg@40tude.net...
> On Tue, 27 Jan 2009 23:28:24 -0500, 631grant cast forth these pearls of
> wisdom...:
>
>> I would give YOUR left nut, Mike, for the simplicity of the 57 Chevy that
>> I
>> once had! )
>> Decision tree:
>> Spark or no spark?
>> Fuel or no fuel?
>> Check points and dwell as well as timing.
>> Check carb jets and float level.
>> Battery voltage and starter.
>>
>> Hmmm, now where is that darn computer? What's a computer???
>>
>
> You sir, better be careful where you're passing out my left nut - or my
> right nut for that matter. Was just trying to say that even the old cars,
> as simple as they were compared to today's computerized cars, had their
> own
> ability to symie. Intermittent problems, conflicting symptoms, quirky
> designs, etc.
>
>
>
> --
>
> -Mike-
> mmarlowREMOVE@alltel.net