69Service Manual – SC5000 04 - Control System
Troubleshooting Steps (4-705 Display Lost Comms)
Refer to the Wiring Diagram “Appendix A: CAN Wiring” on page 138 for wire tracing information.
1. Measure the resistance between pins 1 and 2 of the X207 CAN diagnostic port located near the MMC.
− If the value is near 60Ω, then it can be concluded that the display is connected, the MMC is
connected, and there are no short circuits between CAN-H and CAN-L. Proceed to Step 2 to check
for shorts to ground.
− If the value is near 120Ω, then is can be concluded that either the display or the MMC are
disconnected (open circuit) from the CAN0 network. Proceed to Step 3.
− If the value is near zero or signicantly below 60Ω, it is likely there is a short between CAN-H and
CAN-L somewhere in the network. Proceed to Step 4.
2. Check for continuity between CAN(0)-H and the main ground lug, and also between CAN(0)-L and the
main ground lug.
− If either value is at or near zero, that circuit is shorted to ground. Proceed to Step 4 to help isolate the
location for repair.
− If both values are not near zero, then testing is inconclusive and either the MMC or display is at fault,
and additional testing will be required (such as polling a connected TrackClean module or using an
oscilloscope) to determine which component is at fault.
3. Open Circuit Tracing:
a. Disconnect J104 from the MMC and recheck the resistance between pins 1 and 2 of X207.
– If the value remains near 120Ω, the open circuit is known to exist at J104 or W136/W135, near
the MMC connector.
– If the value changes to open-circuit, then the open circuit is located toward the user interface.
Continue to next step.
b. Reconnect J104 and disconnect the J10/P1 harness connector located inside the base of the
steering column. (Continue).
c. Check the resistance between pins 11 and 12 of the J10 (machine side) connector.
– If the value is open, repair or replace the harness between J10 and J104.
d. Check the resistance between pins 11 and 12 of the P1 (steering column side) connector.
– If the value is open, repair or replace the steering column harness.
4. Short Circuit Tracing:
a. One at a time, disconnect J102 (if present), J109, and nally J104 from the MMC, and recheck pins
1 and 2 of X207 for a short circuit.
– If the short circuit cleared when you disconnected J102, repair or replace the harness leading to
the Li-Ion battery.
– If the short circuit cleared when you disconnected J109, repair or replace the harness(s) between
J109 and the TrackClean module.
– If the short circuit cleared ONLY when all 3 connectors were disconnected, then there is an
internal fault in the MMC. Replace the MMC.
– If the short circuit remains, continue to the next step.
b. One at a time, disconnect J7 at the battery charger, and J10 to the column harness, and recheck
pins 1 and 2 of X207 for a short circuit.
– If the short circuit clears when J7 is disconnected, replace the battery charger.
– If the short circuit clears when J10 is disconnected, repair or replace the column harness or
replace the display.
– If the short circuit persists, repair or replace the main harness.
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