TJA1054T CAN override HELP

Thread Starter

Priker

Joined Jan 26, 2021
3
Hello everyone, I’m new to this forum and not sure if this post is in the right place, feel free to move if necessary.
We have a motorized seat ECU made by Bitron for use in a vehicle with CAN communication. We are trying to force the ECU to an (on) state without the CAN connection. I have opened the ECU and found the CAN connections go into a TJA1054T CAN transceiver first. Does anyone know a way to force this transceiver to wake up without the CAN connection to the vehicle BCM? I tried to apply a (low) signal to the wake terminal on the chip but it did not wake up the ECU as I had hoped. Any help or suggestions would be greatly appreciated.
Thank you, Peter.
 

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Papabravo

Joined Feb 24, 2006
16,132
It probably has little motivation to wakeup if there is nothing connected to the CAN bus. What evidence do you posses that this is possible? It is just a transceiver after all.
Notice that the "FAILURE DETECTOR" is looking at the state of the CAN Bus lines.
 

Thread Starter

Priker

Joined Jan 26, 2021
3
It probably has little motivation to wakeup if there is nothing connected to the CAN bus. What evidence do you posses that this is possible? It is just a transceiver after all.
Notice that the "FAILURE DETECTOR" is looking at the state of the CAN Bus lines.
I don’t know if this is possible or not, just looking for some help to figure it out, one way or the other. Do you have any ideas that might get this ECU to power up? Maybe bypass the first CAN transceiver somehow?
 

Papabravo

Joined Feb 24, 2006
16,132
I don’t know if this is possible or not, just looking for some help to figure it out, one way or the other. Do you have any ideas that might get this ECU to power up? Maybe bypass the first CAN transceiver somehow?
Not really. You have given us the pinout and block diagram for the transceiver. That is really not enough to infer what might be required to power the unit up. It does not seem reasonable to me to focus on the transceiver. Do you know anything about how CAN communication works?
 

Thread Starter

Priker

Joined Jan 26, 2021
3
Not really. You have given us the pinout and block diagram for the transceiver. That is really not enough to infer what might be required to power the unit up. It does not seem reasonable to me to focus on the transceiver. Do you know anything about how CAN communication works?
Yes, I understand the fundamentals of CAN communication within the automotive field. Do you have some other idea that would help out if the CAN transceiver is not the place to start?
 

Papabravo

Joined Feb 24, 2006
16,132
Yes, I understand the fundamentals of CAN communication within the automotive field. Do you have some other idea that would help out if the CAN transceiver is not the place to start?
So you know that a lonely node on a CAN network will retry a transmitted frame FOREVER because there are no receivers to verify the frame and give a dominant bit in the ACK slot. Similarly, a device such as an ECU controller may be expecting to receive something before it can complete it's power-up reset sequence. I'm sorry that I am not familiar with your particular hardware. Maybe one of the other members is familiar and a full schematic of the ECU would be helpful.
 
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