Can Switch board V3 for Dual EGT on Mazda RX7

Hello all,

I’m using a Can Switch Board V3 on a Link ECU G4X (because Link Ecu handle the Oil metering Pump) on a Mazda RX7 FD3s
All the classic Inputs are used, so I added a CAN Switch Board V3 to plug 2x EGT sensor on it

The problem is… no CAN informations report to the Link ECU
I already asked the Link Forum, he checked and told me everything was fine in my setup (There is already a setup file for the Switch Board V3 in the Link software)
He tried my tune on a bench and send voltage in Can An1 and it is working, so I guess my problem come from my switch board

"Your ECU config is correct now as far as I can see. I tested on the bench in an ecu using the same old firmware version you are running, sending 00FF on ID 0x640, the ecu correctly receives 0.255V on CAN AN1. "

The switch board is turning on (orange led), no problem here
I jumped the 5V in the Analog input 1 to make sure the problem doesn’t come from somewhere else (EGT sensor etc)

But the CAN AN 1 input still report 0V

Did I am missing something ? Except the wire connection I touched nothing on the switch board, ID1/2/3 and Speed Jumper are still open, same for the termination, still open

I don’t have the Light Client software because I have nothing to connect the “CAN to USB, but the manual said :
Jumper ID3 is responsible for entering
compatibility mode. If it is open then
CAN Switch Board is configurable
using Light Client (speed, base ID,
rotary switch configuration) software
and the device sends data using new
V3 data format. The default speed is
500 kbps and base ID is 0x640.
When the ID3 jumper is closed with a
solder joint, the device enters
backward compatibility mode and can
be configured using jumpers.”

So the switch board should be in the standard V3 format right ?

Is it because of the 120 ohm termination still open ?
Or maybe I can’t do without the software with ID3 open ?

Thanks for your support !

What is your CANbus speed?
The default speed of a CAN Switchboard is 500kbps.


Canbus speed is set to 500kbit/s

Do you have proper termination of the CANbus?
Do you have any other devices on this CANbus?

Sorry but what do you mean by termination ?
I got a 12V from ignition and Chassis ground which goes to the board directly
Can L and Can H goes directly to the can pin from the Link ECU

For the devices I have 1 EGT in An 1, 1 other EGT in AN2
Both EGT signal come from an Amplifier which convert Type K sensor in analog 0-5V signal
This 2 EGT are ground goes to the SGND from the switch board
(I’ve only tested with 1 EGT at this time)

Here is the wiring I’ve done :

I checked tutorial on Youtube, because CAN is totally new for me, and I think I forgot the resistance…
Do I just have to close the jumper termination on the board or do I need to also had an other resistance somewhere else ? (just before the ECU connector ?)

You need 120 Ohm resistors on both ends of the CANbus. Please see the screenshot from the CAN Switchboard User Manual:


Please solder the T (terminator)jumper, like in the screenshot below.
For short CANbus length and 500 kbps, one should work fine.

Add the second resistor later for the Link ECU side.

Ok I jumped the termination, and I shielded the CAN cables to be sure, and still 0V…

EDIT : Ok I found the problem…

On your Switchboard CAN H is Green
On the Link ECU G4X, CAN L is Green

I swapped the 2 CAN Bus wire… what a moron I am

I put them back in correct position and now everything is working…

Thank you for your help !