Finding chassis CAN
The factory CAN High and CAN Low wires show up in several places in the car. The easiest spot to tap into is the D43 junction connector. Think of it as the car's CAN hub. The modules that talk over CAN all meet there, so you get a clean connection without cutting into a module's own loom. Check the factory wiring diagram for your model year to find the D43 and confirm which pins carry CAN High and Low.
Need the junction diagram? Ask us and we'll send it over with advice for your build.
Wiring it to the Haltech
Run the chassis CAN High and Low from the D43 to the ECU. We like to keep the factory vehicle CAN on the ECU's main connector and leave the auxiliary connector's CAN for Haltech devices such as dashes and wideband controllers. Keeping the two buses separate avoids conflicts.
On the ECU used in this setup, the main connector pins are:
| Pin | Signal |
|---|---|
| B23 | CAN High |
| B24 | CAN Low |
Always check against your own ECU's pinout before you crimp anything. Twist the pair along its run and make solid connections, since a flaky CAN splice causes strange, intermittent faults.
Setting the protocol
- In the software, go to Main Setup and open the Devices section.
- Pick the FR-S / BRZ vehicle CAN protocol. There are two: one for cars with automatic climate control and one for manual climate control. Choose the one that matches your car.
- Go through the list of functions the protocol supports, and for each one you want to use, change its input from analog to CAN.
- Save, power-cycle and watch each CAN-sourced channel live to confirm it reads correctly.
Common problems
- No data at all: CAN High and Low swapped, or connected to the wrong ECU bus.
- Some functions work, others don't: that function's input is still set to analog.
- Odd or missing readings from the climate side: check you picked the auto vs manual climate protocol that matches the car.
More on the wider topic in our vehicle CAN support article, and see ECU grounding dos and don'ts before you finish the loom. Doing a similar job on a Mazda? See our NC Miata write-up.
