Idex Hale Sam, Technical Manual

Page: 190 / 223

170
Shorted Diode
If the diode reads low resistances in both directions, this is a sign that the diode is shorted. A di-
ode should not measure low resistance in the reverse biased direction. The diode should be re-
placed in the circuit.
4.16.3
General CAN Troubleshooting
DO NOT ALTER THE CAN NETWORK COMMUNICATIONS (SAE J1939 CAN BUS) OR CON-
NECT OTHER DEVICES TO ANY OF THE CAFS, CAPTIUM, FOAM, OR SAM CAN BUS BACK-
BONE(S).
Perform the following to troubleshoot CAN connectors/connections.
A.
Verify all connectors are secure and correct.
PIN A – CAN HIGH – Yellow
PIN B – CAN LOW – Green
PIN C – CAN SHIELD – BLACK
B. Verify there are no missing/unplugged terminating resistors (Figure 138).
Figure 138. Terminating Resistor
C. Measure resistance between CAN H and CAN L. See Figure 139.
Figure 139. Bus Termination Test Setup
D. Verify multimeter indicates 60 ± 1 0 Ω s.
NOTE
Measure at multiple points (middle as a minimum) of the network, if possible. The
measured value should be nearly the same at each point within the network.
If the reading is below 50 Ω: ensure there is NOT a short circuit between CAN H and CAN L wir-
ing, and there are NOT more than two terminating resistors in the bus under test.
If the reading
is higher than 70 Ω: ensure there are NOT any open circuits (broken wires or bad
connectors) in the CAN H or CAN L wiring path for the bus under test, and your bus has both ter-
minating resistors (one connected at each end) and each terminator measures 120 Ω (when
connected directly to the multimeter).