Troubleshooting

RENR2696-01 147
Troubleshooting Section
The ECM receives electrical power (battery voltage)
through the wir
ing within the engine harness.
The ECM input at connector P1:70 (keyswitch)
receives battery voltage from the keyswitch when
the keyswitch
is in the ON position or the START
position. The ECM will power up when the ECM
detects battery voltage at the keyswitch. The ECM
will power do
wn when battery voltage is removed
from the keyswitch.
Thecauseofa
n intermittent power supply to the ECM
can occur on either the positive side (unswitched
+battery) or the n egative side (battery negative). Both
sides are ro
uted from the ECM to the battery. The
three connections for the unswitched +battery should
be routed through a dedicated protection circuit.
TheengineECMrequiresthekeyswitchtobeinthe
ON position in order to maintain communications.
Temporarily bypassing the engine wiring may be an
effective means of determining the root cause of
intermitt
ent problems such as intermittent shutdowns.
If the symptoms disappear with the bypass wiring, the
engine wiring is the cause of the problem. A means
of bypassi
ng engine wiring is explained in this test
procedure.