Trigger power to my Dashcam ignition wire based on vehicle Ignition from CAN high Pin on the j1939 port.

That trigger module is not designed to look at a CAN signal. It's not certain but it might work better if connected to CAN-L.

CANbus has CAN-H and CAN-L, and the voltage between the two is near zero (recessive) and about 2 V (dominant). When there bus is recessive, both voltages are about 2.5 V, but that can vary a quite a bit and is not well defined, and CANbus ICs from different manufacturers will give different voltages.

When a vehicle is off, the bus will be in a recessive state.

CAN-L will be around 1.5 V when there is a dominant signal, which might be enough to trigger that TR-4 module.

To trigger the dashcam when the ignition is on, you should either detect more than 1 V between CAN-H and CAN-L, or detect more than about 13 V on the supply voltage. Either way, you need a time delay, but the TR-4 module has that.

Forgive my rudimentary knowledge, I have worked with and around a lot of IOT and electronic devices but mostly programming. When you say "you should either detect more than 1 V between CAN-H and CAN-L" can I connect both pins going in to the trigger input of the TR4 or is doing that interfering with other device's data processing?

markarupert said:

Forgive my rudimentary knowledge, I have worked with and around a lot of IOT and electronic devices but mostly programming. When you say "you should either detect more than 1 V between CAN-H and CAN-L" can I connect both pins going in to the trigger input of the TR4 or is doing that interfering with other device's data processing?

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No, connecting CAN-H to CAN-L will stop any communications.

I meant that when CAN-H is more than 1 volt higher than CAN-L, that shows that something is transmitting on the CANbus and the vehicle is operating.