Navistar N9, Diagnostic Manual

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46 1 DIAGNOSTIC TROUBLESHOOTING PROCEDURES
Step
10
Determine if power circuits to the ECM are working properly. Decision
A. Key-On Engine-Off (KOEO)
B. Measure voltage between battery ground and pins C-1, 3 and 5
Are power circuits between pins C-1, 3 and 5 and battery ground within 0.5V of
battery voltage?
Yes: Go to Step 11
No: Diagnose and repair ECM
power circuit (40A fuse, ECM
PWR Relay, etc.). After repairs
are complete, retest for original
problem.
Step
11
Determine if Public CAN circuits between ECM and Diagnostic Connector
are Open or have high resistance.
Decision
A. Key Off
B. Disconnect Batteries
C. Measure resistance between 9-pin Diagnostic Connector pin-D and
ECM pin C-62 (CAN-L)
D. Measure resistance between Diagnostic Connector pin-C and ECM pin
C-61 (CAN-H)
Are measured resistances 5 ohms or less?
Yes: Go to Step 12
No: Repair open or high resistance
in Public CAN circuit(s). After
repairs are complete, retest for
original problem.
Step
12
Measure resistance between Public CAN circuits. Decision
Measure resistance between Diagnostic Connector pin-C and pin-D.
Is resistance between Diagnostic Connector pin-C and pin-D approximately 60
ohms?
Yes: Go to Step 14
No: Go to Step 13