Zapped
There are many ways one could be
“zapped” by electricity, and one way that it
happened to Jesse Zacarias from Elec-Trans Diagnostics in
Gilroy, Calif., goes like this. A 2003 Dodge Ram truck equipped
with a 5.9-liter Cummins diesel and a 48RE transmission came
into his shop with a complaint of taking off in 3rd gear. The
park and neutral gear-select indicator lights were the only
ones that would illuminate. With any scan tool, Jesse could
retrieve a code P0700 (transmission fault present) from the
engine-control module but could not communicate with the
powertrain-control module for the transmission.
He verified that the PCM was not grounding
the relay circuit pulling voltage from pin 1 at the
transmission connector, which means it was in failsafe. Power
and grounds were verified by back-probing the C1 connector in
the PCM.
At one point during this pin-point check at
the PCM, Jesse had his positive lead probed into the #30
terminal in the C2 connector to monitor the PCM’s control
of the relay. This is the circuit from the relay that the PCM
grounds to energize the relay coil, which in turn snaps
internal contacts together to send power down to pin 1 at the
transmission connector, supplying power to the OD, TCC and
governor solenoids.
He decided to pull the lead from his meter
while the other end was still connected to wire 30 in the PCM,
and he tapped it to ground. When he put the lead back into his
meter he saw 0.1 volt, which meant the circuit remained
grounded by the PCM. He took it for a road test and it shifted,
the PRNDL lights returned to normal, his scan tool could access
the PCM and he had no codes.
Once he cycled the ignition, all his
problems came back. And he could repeat tapping the #30 wire in
the C2 connector and the computer would hold the ground and
work flawlessly. So he concluded that his PCM was faulty and
bought a new one, and guess what happened – you are
absolutely right! Something similar must have happened to you.
He still had the exact same problem.
So it was back to basics. He started
checking his power and grounds again, but this time he learned
a very good lesson: When you’re checking for power and
grounds at the PCM, back-probing is not enough. When he
unplugged the C1 connector and checked pin 22 on the face side
of the connector, he had only 1.8 volts, but on the back side
of the connector he had 12.9 volts.
After pulling the connector apart he
realized what had actually happened. The air-conditioning
condenser is mounted right next to the PCM and C1 connector
(figures 1 and 2), which allowed for condensation to seep into
the connector and compromise the wire connecting to the
terminal. Jesse bought a wiring harness for $155, and the
problem was resolved – that is, until the condenser gets
it all wet again, and over time it may find itself in your shop
for the same problem. Will you get zapped the way Jesse did?
Connector repair kits are available from
the dealer (figures 3-5). The part numbers are:
Connector C-1 (black) ..................
56017957
Connector C-2 (white) ..................
56018614
Connector C-3 (gray) ...................
56018615
Wire package (40 wires) ..............
04882087
Connector cover ...........................
56018606
Connector plug
............................. 56038347
©2006 Transmission Digest