7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS 381
ECM PWR (Electronic Control Module Power)
Figure 424 Function diagram for the ECM PWR
The function diagram for ECM PWR includes the
following:
•ECM
• ECM main power relay
• Ignition switch or power relay
•Battery
• Fuses
Function
The Electronic Control Module (ECM) requires a 12
V power source to function correctly. The operating
power is received from the vehicle batteries through
the ECM main power relay contacts each time the
ignition switch is turned ON.
When the ignition switch is turned ON, the ECM
provides an internal ground to the coil side of the
ECM main pow er relay. This closes the relay contacts
and provides the E C M with necessary power.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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