Troubleshooting

RENR2696-01 151
Troubleshooting Section
g00954776
Illustrat
ion 67
Bypass harness
Note: This bypass harness is only for test
applications. This bypass harness may be left only
temporar
ily on the engine. The bypass harness
can be used in order to determine if the cause of
the intermittent problem is the interruption of the
power su
pply from the battery to the ECM or to the
keyswitch circuit.
A. Turn the
keyswitch to the OFF position.
B. Disconnect harness connector J1/P1 from the
ECM.
C. Removethe20Ampin-linefusefromthebypass
harness
and connect the harness to the ECM
connector J1.
Note: Th
is bypass directly connects the circuit for the
keyswitch to the ECM. The ECM will remain powered
until the connection to the unswitched battery line “+”
is disc
onnected from the battery post. The removal of
the 20 Amp fuse will ensure that the ECM will remain
without power while connections are being made.
The20A
mp fuse should also be removed before
disconnecting the battery connections.
D. Conne
ct an electronic service tool to the Data
Link connector. Connect the unswitched + battery
and the negative wire of the battery directly to
the ba
ttery posts in order to ensure the correct
polarity.
E. Replace the 20 Amp in-line fuse. Verify
that communication from the service tool is
establis
hed. Perform any necessary diagnostic
tests.
F. Remove th
e20Ampin-linefuse.Disconnectthe
bypass harness. Restore all wiring to the original
condition. Replace the fuse in the disconnected
bypass h
arness.
Expected Result:
Installing the bypass eliminates the problem.
Results
:
•
OK – The symptoms disappear when the bypass
harness
is installed. Also, the symptoms return
when the bypass harness is removed. The problem
is in the wiring that supplies power to the ECM.
Repair
the wiring that supplies power to the ECM.
STOP.
•
Not OK