Figure 5-1 - Incorrect Can Bus Topographies; Figure 5-2 - Correct Can Bus Wiring Example And Node Connections - Garmin G3X Touch Maintenance Manual

3. Ensure proper installation of the CAN bus and that the following guidance was adhered to during
installation:

The CAN bus backbone must be a single linear path with exactly two distinct ends. CAN bus
connections must be "daisy-chained" from device to device. Avoid "star" and "Y" topologies, and
do not use a hub device. Reference Figure 5-1.

The overall length of the bus must not exceed 100 feet.

Ensure any existing part number M27500 wire if retained for the CAN bus wiring does not
exceed 60 feet in overall length.

Do not connect more than one device to the CAN bus backbone at the same point. Instead,
daisy-chain the CAN bus backbone from one device to the next.

Observe proper wiring, shielding, and grounding requirements as described above.

Terminate the CAN bus at the two extreme ends of the bus, as described above.

When adding a new device to the CAN bus, evaluate proposed modifications to the CAN bus
wiring connections to ensure compliance with all above requirements and the G3X Touch EFIS
Part 23 AML STC Installation Manual (190-02472-01).
4. Ensure the CAN bus is terminated in only two locations, and only at the extreme ends of the CAN
bus.
Figure 5-2 – Correct CAN Bus Wiring Example and Node Connections
5. Ensure the G5 (if installed) is not at either extreme end of the CAN bus as the terminator.
6. With power removed, remove a connector from one of the devices that is not located at either of the
extreme ends of the CAN bus.
NOTE
Do not perform this test on the G5 (if installed as a standby flight display).
a. Using an ohm meter, verify that the resistance between the CAN HI and CAN LO pins on the
connector is 60 ohms. This will verify that the CAN backbone is properly terminated at each
end (two 120 ohm terminating resistors in parallel).
b. A resistance of 120 ohms indicates that one of the two required CAN terminations is
missing.
c. A resistance of 40 ohms or less indicates that too many terminations are installed.
Maintenance Manual
G3X Touch EFIS Part 23 AML STC
Figure 5-1 – Incorrect CAN Bus Topographies
Page 33
190-02472-02
Revision 2