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Finally, something challenging… Wait a sec though… My mind enjoys the workout, but it doesn’t do much for my pocket book. Why is it that so many managers are afraid to charge customers for their techs time as he or she unravels the mysteries buried deep inside the metal walls of the vehicles onboard computer? Perhaps someday we will all get paid properly for our diagnostic skills, but for now, we need to go in, diagnose the problem, and then up sell needed maintenance work hoping to make the job worth our time. |
So lets dive in on this one. Sure enough, the MIL was on and
the starter drive would disengage from the flywheel after cranking the engine
over for just a second. It took a few minutes, but I finally got the engine to
turn over long enough to start. Now that the truck is in my service bay, lets
look at the stored Freeze Frame (have to have one MIL is on) and the associated
Failure Record(s).
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When viewing this screen, remember that there are 5 Failure Record slots and 1 Freeze Frame slot. Failure records will be updated as new failures occur (over writing the old data), but Freeze Frames will not. Failure Records are stored in a FIFO (first in first out) method. The Failure Records will be listed in order of occurrence from the bottom up. In other words, the P0341 set FIRST. If it were a type A DTC, it would also have set the Freeze Frame at the same time. |
Now lets look at the DTC Info Screens:
As you can see, both diagnostics passed on the last test
performed. They also both passed this ignition. They both have pass and failure
counts and both have set. Now lets look at the data starting with the Freeze
Frame Data:
The Failure Record Data for the P0341 was exactly the same as the Freeze Frame Data for the P0341.
Now lets look at the Failure Record Data for the P0335
Ok, the DTC set criteria for both the CKP and CMP I don’t
think is that important right now. What we do know is that however the PCM
monitors their performance, it found something it didn’t like. Now this
particular truck with this particular engine is strange… If you take the trouble to see where the CKP signal comes
from and where it goes for a 95, 96, and 97 I think you’ll be surprised.
Somebody kept changing his or her mind…. <g> Anyway, I peeked at the
current engine data and found CMP Active Counters and CKP Active Counters. This
tells me what? Hint: why don’t the all have
those? I found I had 30 or so CKP-CMP resyncs.
Now go back and look at the data. With the above information, you should have
some thoughts.
I will follow this post up with
more information and some waveforms, but my main purpose here is to demonstrate
why enable criteria and such are not the ABSOLUTE
NECESSITY some of the aftermarket LOBBIESTS say they are.
Sure, it would be great to have them and I hope you all have access, but until
the day comes that we get paid to dig through all the material and spend half
the day diagnosing a failure, we need to take a step back and as Mac
Vandenbrink says, “Analyze, don’t memorize!!” I love that line…. <g>