Service Manual

Electrical Sysem
6-14 627333-A
FIG. 6: CAN Harnesses
1. Stub Cabling
2. T-Connectors
3. Terminators
4. J1939 Backbone
FIG. 7: Back Harness Connector
Pin A to C should be 2.5 volts.
Pin B to C should be 2.3 volts.
Pin A to B should be 0.0 volts.
1. A - CAN High (yellow)
2. B - CAN low (green)
3. C - CAN shield (grey)
I/O module connectors: J2 (gray) and J3 (black).
CAN backbone Harness - Gray connectors are located
under right rear corner of the cab - one for chassis and
one for system. Connectors can be disconnected one
at a time to isolate problems down to system or
chassis. Check for CAN high and CAN low on these
connectors. Check for power on pin D and ground pin
E. Always check pins for moisture, corrosion and loose
pins.
Example: Once problem is isolated down to system or
chassis, further testing can be done.
• If problem is on system side, check furthermost
end of system backbone harness - taillights.
Disconnect cable going into tee connector.
• If chassis starts working, problem has been
isolated to taillight tee connector or cabling.
• If problem still exists, taillight system has been
eliminated.
• Repeat procedure at next tee connector forward
until problem is found.
Must do a battery disconnect every time when plugging
or unplugging CAN network.
FIG. 8: Chassis CAN Bus Power Connector
FIG. 6
Q000088S
3
2
4
1
FIG. 7
Q000089S
3
2
1
FIG. 8
Q000090S
1
5
4
3
2
CAN BUS POWER CONNECTOR
CAV CABLE
END
COLOR CABLE
TAG
A (1) 1A YEL 1290
B (2) 2A GRN 1291
C (3) 3A GRA/BLK 1292
D (4) 8A RED 392
E (5) 9A GRA 397