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CAN Network Modification Question

CANBus Communications Decoded

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Hi Guys, First time poster, so be kind! Anyway, i am converting a GMC Safari to Electric using the Ingenext Module setup that some of you may be familiar with. It uses 3x CAN networks for various segments of the controller, one of which is obviously between the Battery and the Control Module. The default branch length for that segment is around 1m and both the module and the battery have built in 120ohm termination resistors.

I am using a Speedhut Canbus gauge for the battery State of Charge, which has been programmed to the correct PiD for this on the network. My issue is that i am not getting any reading on the gauge, so i suspect nothing is being picked up from the Can Network.

Ingenext advise that and "trunks" over 1m in length have a 720ohm termination resistor fitted. I didnt have one of those when i setup the new truck, so i have used another 120ohm resistor in a deutsch dtm end fitting for the end of trunk termination. The new trunk is around 3.5m long to the dash from the rear of the vehicle. I assume that either the new trunk length or the 120ohm resistor not being sufficient may be the problem, but any thoughts guys?

Cheers

Mike

I'm pretty sure the spec is two 100-120ohm resistors total on the bus (one at each end). You with things powered off, you should be able to measure a total resistance of 40-60 ohms on a working bus. If it's less than that, you have too much termination and some devices may not be able to drive the bus (requires more current to raise the voltage).

Two most common failures when attaching a new device -- wrong bus speed (baud rate), or the CAN high / low signals are swapped.

Thanks David, That is what i thought too. Is the 720ohm resistor usual in a CAN network?

I will check the connection and baud rate!

Mike

I would think the 720 ohm is a typo, and they meant 120 ohm.

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