openinverter forum

Returning from an MOT test to actually have a fully functioning and road legal BMW Z4 with zombieverter and GS450h transmission and the car started playing up.

Long story short the 12v battery voltage was so low that everything went haywire.

Before discovering this and as it was pouring with rain I took the vcu out and tried to down load to an earlier software version on my test bench and happily I connected 12 volts to pin 28 and ground to pin27, yep what an idiot.

Anyway this resulted in a loss of Can 1 that the IVT shunt was connected to thus giving a precharge fault as no HV was showing. I have tried replacing IC16 transceiver which is connected to pins 27 and 28 but no luck there, the 120 ohm resistor is ok and I believe the connections from IC16 go straight to the STM32 so not much else to check with my skill set.

Connecting the IVT shunt to canbus 2 with the vehicle canbus, which interfears with the IVT shunt, programmed to can1 gives a full set of hv readings. Run is showing in the software and the oil pump is happily humming away. There is an output from my inverter relay as well. Selecting drive or reverse also shows as selected in the software but the car does not move.

Questions are,

Must the IVT shunt be connected to Can 1 for the car to run or will Can2 do (assuming you move the can wiring to the relevant Can terminals on the VCU) i.e. does the shunt need to put its can input into the STM32 through Can input 1. So would this cause the car not to move?

Is there anyone who can check and repair the vcu I am happy to pay for a repair if that is what is needed? I am based in the Andover area.

Thanks

The only idea which I have: There is some room for confusion with the type of the CAN transceiver. In the schematic it is SN65HVD234, but in the comment it is a SN65HVD230. The difference is how the pin 5 needs to be connected. And finally, to make the confusion complete, I have on my desk some pieces which are labeled as SN65HVD234 but behave like the SN65HVD230. So maybe it helps to try out different connections of the pin5 (open, ground, or 3.3V). And to measure the CANH, CANL and the TX and RX pins with an oscilloscope, to understand what is going on.
BTW: The CAN transceiver is specified that it should survive 16V on both CANH and CANL, so I would expect you cannot destroy it by applying 12V to it.

Interesting that 16v limit is ok. I don't have an oscilloscope but savvy can shows activity from the IVTs on can2 but not Can1. I will try your suggestion re pin 5 and get back to you.

So near yet so far!!!

I have checked pin 5 of the SN65HVD230 I used and it does not need to be connected to anything which is the same as the VCU.

Can anyone confirm if the IVT is connected to Can 2 it will work as long as the vehicle canbus is not connected as well? If it will work I am probably chasing 2 problems, faulty Can 1 and something else.