Power Source#

Fuse Tap (xnor harness)#

The xnor harness includes a fuse tap, keeping the OBD-II port free and simplifying cable management.

1. Unscrew two Torx T20 screws and remove the passenger footwell cover
2. Locate the fuse panel tucked behind

3. Remove the fuse from slot F33 (constant 12V, 10A red fuse). Set the fuse aside.
4. Plug the fuse tap into the F33 slot. The wire should point toward the AXM (front of car). Orientation matters.
5. Check the fuse tap’s two fuses:

• Upper 3A fuse — powers the comma device. Leave it in place; it doesn’t affect the car circuit.
• Lower fuse — ⚠️ if it’s a yellow 20A fuse, remove it and insert the red 10A fuse you pulled from F33 instead.

6. Plug the 4-pin Molex connector into the harness box
7. Tuck the harness and wires
8. Reattach the passenger footwell cover

Disconnecting AXM Power#

This section only applies if you have a comma.ai harness (not an xnor harness) and want to power it via a fuse tap instead of the AXM. If either condition doesn’t apply to you, skip this section:

• xnor harness — already uses a fuse tap and never draws power from the AXM.
• comma.ai harness left on Comma Power — draws from the AXM by design; nothing to disconnect.

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 (fuse tap) often resolves this.

1. Remove the harness from the car (easiest), or use the sleep method to ensure no power runs through the harness
2. Remove the harness box from the rest of the harness
3. In the wiring connector, locate the two red power wires. These are side-by-side in the connector center.

4. Use a jeweler’s tool to lift the locking tabs above each wire and gently pull them out of the connector housing
5. 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.