december2021 - 63

The test that was recommended by all the information
systems specified a resistance test that had to be
measured at the PCM connector. The specific resistance
specification for a good solenoid is 1.7 ohms. With the
computer connector removed, Bill performed the test,
finding that all the solenoids measured 1.7 ohms at the
recommended temperature range.
Bill was perplexed by the test reading. He thought
that one of the solenoid readings would be different since
the computer was throwing a DTC and was in limp mode.
He shared the problem with me and got me up to speed
on the test results. I am not a big fan of resistance testing
in most cases, and this was one of those. I suggested to
Bill to connect an amp clamp and scope the current to
compare a good solenoid to the suspect solenoid. The
comparison game is a good one to use since it is a direct
comparison between a good and suspect component.
Bill proceeded to reconnect the wire harness connector
to the computer so he could start the engine up and test
the current draw of the solenoids. With two amp clamps
attached to the eScope, he came up with the waveforms
that told the whole story. After we reviewed the results, Bill
was still unsure if he should pull the trigger on such an
expensive part. The reason he was thinking that way was
that the recommended resistance test passed. I reminded
him that the resistance test was not valid in this case since
the dynamic nature of the current draw test revealed the
solenoid was drawing 19 amps.
He knew that he was the tech who would be speaking
to the customer and had to make the correct recommendation.
Bill asked for my take; I believed it looked
bad and there was a possibility that the wire could be
shorted, but the more probable cause was that the solenoid
was shorted internally because the current indeed
" ramped up " (as inductors should).
I suggested to Bill how to confirm if the wire was
good and the solenoid was bad. He would have to remove
the wire for the high current draw solenoid and switch it
with a known-good solenoid wire. If the reading from the
suspect solenoid wire was good while energizing one of
the other known-good solenoids, then the wire was not
shorted. That would prove the solenoid was the problem.
There are so many different connectors that have
different release mechanisms, and along with the dirt
and warpage, it becomes a big pain in the butt removing
wires from a connector plug. With a bit of patience
and time, Bill successfully removed the wires from the
computer connector and switched the bad one to a good
one. He took the wire from the high-drawing solenoid
(19 amps) and moved it to another solenoid (low-current
drawing, 7.9 to 8.5 amps) and did the reverse by installing
the wire from a proper-working solenoid and on the
high-drawing solenoid.
The results were that both the wires were confirmed
good while the high-drawing solenoid was
confirmed bad. Understanding the circuit and using
simple logic nailed down the correct diagnosis. The
circuit that was pulling the 19 amps was caused by a
shorted solenoid, resulting in the DTC and limp mode.
Our pinpoint test confirmed the actual problem was
the solenoid. Bill was now confident to make the call
to the vehicle owner and explain the problem, along
with selling him the necessary repair.
With the owner's approval, Bill removed the valve
body, ordered a new one from the Dodge dealer, and
installed it. After the installation of the new valve body,
The VE test confirmed that the MAF was underreporting,
so Bill ordered an OE replacement part from
one of our distributors.
With the new MAF installed, the VE test was repeated
and looked just about perfect. But the MIL was still
illuminated, which would prevent the vehicle from passing
an emissions test. Bill found that there was a TSB
NTB12-051k regarding PCM Reprogramming for MAF
code P0101. He performed the procedure that extinguished
the MIL, but there was still a problem. With
the MIL off, the vehicle was test driven multiple times
trying to set the monitors to " Ready " only to come up
with the same issue of " Not Ready. "
With a customer who was starting to lose faith, Bill
filter, and fluid, we rechecked the current draw from the
same solenoid's circuit. We found that the new solenoid
current draw was 8.5 amps.
With the MIL extinguished and the vehicle out of limp
mode, it was time to test drive the vehicle. After a few successful
test drives, we were confident that the root cause of
the fault was rectified and the vehicle could be returned to
the customer.
2011 NISSAN PATHFINDER
Our next difficult vehicle was a 2011 Nissan Pathfinder
4.0L that came in with the customer complaint of
the MIL on and a low-power issue. After connecting
our scan tool, we uncovered one of the most common
DTCs on a Nissan vehicle, a P0101 " Mass Air Flow
Sensor Range/Performance. " Freeze frame indicated
the following:
* 712 RPMs
* MAF = 3.5 GPS (that is under the 1 gram per liter
rule on a normally aspired engine).
After reviewing the freeze frame information, Bill
knew the next thing he should check was the condition
of the air filter and the MAF sensor itself. After the
inspection, Bill decided to check the actual volumetric
efficiency (VE) of the engine using the eScan VE test.
thought that the next best thing was to drive to the Nissan
dealer and purchase a new MAF. However, the part
number on the new Nissan part did not match the original
MAF that Bill had already replaced. The Hitachi sensor
sold by the distributor as the OE part had a different part
number than the dealer's. This was a first for us. With
the second new MAF installed, the vehicle was test driven
again only to report the same results, monitors " Not
Ready. " The pressure was on and Bill had to think fast.
He contacted the Nissan hotline, which told him to
remove the battery cables with the key off and touch the
cables together for a few minutes. This should reset the
computer back to base settings. I always teach this very
thing in my classes, but I add an extra step for safety. I
advise connecting a 1 ohm 10-watt resistor in series with
the battery so the computer capacitors can be drained
slowly (rather than instantaneously, possibly spiking the
computer and causing damage). Using the resistor is a
preferred method that many OEs recommend for setting
the computer system back to the base setting.
With the procedure completed, the three monitors
that were not able to run before (and even after a
dealer MAF was installed along with the PCM being
programmed) were finally able to run. The OPUS IVS
support line Nissan tech told Bill that they have documented
this issue before and suggested to only use the
MAF purchased from the dealer. They suggested verifying
it is the same part as the one being replaced.
This was a lesson learned and one remembered.
Always RTFI (read the friggin' information) and follow
the procedure.
G. Jerry Truglia is an ASE World Class Triple Master
Technician Auto, Truck & School Bus, L1, L3, F1, A9, X1 C1.
December 2021 | FleetMaintenance.com
63
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december2021

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