Who this is for
Left-hand-drive Tesla owners on sunnypilot who want steering to stay active when they brake.
comma fourcomma 3X
xnor wikiHardware and wiringAdvanced
Tesla vehicle CAN add-on cable for sunnypilot
Two extra wires into the comma harness plus a plug on the right A-pillar let sunnypilot keep steering on while braking.
You need
- A Tesla A or B harness already fitted
- The add-on cable from xnor.shop
- Trim tools for three A-pillar panels
In plain words
Why this guide matters
On a Tesla, pressing the brake turns stock openpilot off completely, so you are stuck with one-pedal driving. This add-on cable adds two wires to the comma harness and plugs into the right A-pillar. With it, sunnypilot can keep steering on while you brake, engaged by a three-finger tap on the screen.
The short version
What the full guide walks you through
Insert the two extra terminals into your comma harness connector.
Remove the A-pillar trim panels to reach the diagnostic plug.
Plug the cable in and route it to the harness.
Enable the stay-on steering option in sunnypilot and use the three-finger tap.
Before you start
- Left-hand drive only.
- Without it, braking turns everything off, so you are limited to one-pedal driving.
The full written guide belongs to xnor wiki. Checked on September 10, 2026.
Quick answers
Questions people ask
Does it work on right-hand-drive cars?
No; it is offered for left-hand-drive cars only. On RHD cars the cable would have to cross the whole car.
Does it work with both HW3 and HW4?
Yes; it fits the Tesla A and Tesla B harnesses from comma or xnor.shop.
Is the cable needed for basic openpilot?
No; steering and cruise work without it. It only matters for keeping steering active when braking on sunnypilot.
Check your car
Cars this guide talks about
Support changes by year and trim. Open your exact car before you buy anything.
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Check your exact car first, then choose software and hardware.
Photos: comma.ai. Guide content belongs to xnor wiki. CommaGuide is an independent guide and is not affiliated with comma.ai or xnor wiki.
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