Power Source#
Two options depending on which harness you have:
Fuse Tap (xnor harness)#
The xnor harness includes a fuse tap, keeping the OBD-II port free and simplifying cable management.
- Unscrew two Torx T20 screws and remove the passenger footwell cover
- Locate the fuse panel tucked behind
- Remove the fuse from slot F33 (constant 12V — recommended) or F34 (20A, front/rear center lamps). Set the fuse aside.
- Plug the fuse tap into your chosen slot. The wire should point toward the AXM (front of car). Orientation matters.
- Plug the 4-pin Molex connector into the harness box
- Tuck the harness and wires
- Reattach the passenger footwell cover
F33 is recommended as the power source. Using constant 12V avoids conflicts caused by the comma device booting simultaneously with the Rivian. If using F33 with a fuse tap that comes with a 20A fuse, swap it to the 10A fuse you removed from the Rivian.
Comma Power (comma harness)#
- Connect the OBD-II end to the driver’s footwell port
- Run the cable around the center console, tucking it into gaps
- Plug the 4-pin Molex connector into the harness box
Disconnecting AXM Power#
If your xnor harness included a fuse tap, skip this section — your harness does not draw power from the AXM.
The harness from comma.ai draws power directly from the AXM, which can cause intermittent ACC, radar, and Driver+ errors. Switching to an independent power source often resolves this.
- Remove the harness from the car (easiest), or use the sleep method to ensure no power runs through the harness
- Remove the harness box from the rest of the harness
- In the wiring connector, locate the two red power wires. These are side-by-side in the connector center.
- Use a jeweler’s tool to lift the locking tabs above each wire and gently pull them out of the connector housing
- Insert both removed wires into a Wago clamp (or other secure splice) to connect them directly to each other. This lets 12V bypass the harness box and comma device, isolating them from AXM power.