Electric transit bus
Electric bus telematics offline, traced to the destination sign controller
By Sebastian Rivera
The short answer
The telematics on this electric bus went silent because a faulty destination sign controller was distorting traffic on the CAN network. The oscilloscope showed distortion at the end of every frame, and disconnecting modules 1 by 1 isolated the culprit.
- Down
- 4 months
- Found
- under 8 hrs
- On the line
- $300K in contract penalties
- Vehicle
- Electric transit bus
- Symptom
- Telematics silent
- Already tried
- Everyone agreed it was a CAN problem. Nobody could say which network or why.
How it was found
- Put the oscilloscope on the network to look at the actual signal, not just the fault codes.
- The capture showed distortion at the end of every frame.
- Disconnected modules 1 by 1, watching the signal each time.
- The distortion disappeared when the destination sign controller was removed.
Root cause
A faulty destination sign controller corrupting traffic on the shared CAN network.
What this means for your team
On a shared network, 1 bad module can disrupt communication for others, so the system reporting the fault is not always the one causing it. Looking at the signal itself shows where to start.