december2021 - 62

CASE STUDIES
Mining for the right data
Know what tests to perform on challenging vehicles to confirm your diagnosis
By G. Jerry Truglia
Photos courtesy of G. Jerry Truglia
E
veryday diagnosing and working on vehicles is a challenge, to say the least. Most days it's a satisfying
experience, but some days are a nightmare. We all have those days no matter how experienced,
well trained, and how good you think you are. You're going to get your butt kicked. Some vehicles
just seemed to be possessed, where nothing you do goes right, or the vehicle still has an issue.
2012 CHRYSLER TOWN AND COUNTRY
The first nightmare was a 2012 Chrysler Town
and Country 3.6L van. The customer complaint
was that the vehicle would sometimes
stall, and the check engine light would illuminate.
My tech, Bill, connected one of our
scan tools to the vehicle and came up with
a P0480 " Cooling Fan 1 Control Circuit/
Open. " At first glance, it seems straightforward
because it is a common problem on
many Chrysler products. When the problem
is intermittent it becomes difficult to
pull the trigger on an expensive component
(such as a totally integrated power
module or TIPM), especially when an
elderly woman on a fixed income owns
the vehicle.
To make sure the TIPM was bad,
we had to test and not guess, so Bill
put together his game plan for how
he was going to proceed and test it.
After many test drives, he still had
not uncovered the problem. One of
the first steps that Bill performed
was what I've taught in my class for
years-make sure the load is good by testing it
first. Bill did just that and applied voltage and ground
to the disconnected fan circuit. He found that it worked
as designed and was not pulling excessive amperage.
62 Fleet Maintenance | December 2021
His next step was to look at the wiring diagram
and hook up the eScope to the terminals of the low
cooling fan relay (while the engine was cold). He then
monitored the signal as it warmed up. With the scope
connected and the engine warmed up, the waveform
confirmed that the relay was not receiving the command
signal from the TIPM. There was no ground
path being provided for the controlled side of the relay.
Bill previously confirmed all the necessary voltage and
ground supply as well as continuity through the load.
The conclusion of his testing after multiple road tests
(cool downs and warm ups) confirmed that the correct
call was to condemn the TIPM. He concluded
that the TIPM's circuit board couldn't complete the
relay's path to ground.
Bill made the right call because the new TIPM confirmed
the fix. With the new part installed and the vehicle
test driven, all monitors turned " Ready " along with the
vehicle passing the NYS inspection without a problem.
2013 DODGE DURANGO
Our next nightmare vehicle was a 2013 Dodge Durango
5.7L that had an illuminated MIL and a P0750 " Low/
Reverse Solenoid Circuit " DTC. The vehicle was stuck
in third gear via limp-home mode. The first step was to
review scan data and freeze frame to see if the information
would shine further light on the problem.
Bill's next step was to consult our service information.
We used ALLDATA, ProDemand, MotoLogic, and
Identifix to see if there was any more information that
could assist his diagnosis. After researching the different
systems and reviewing the wiring diagrams, Bill located
the correct pins and proceeded to perform the recommended
test.

december2021

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