We mentioned earlier that nay node can transmit an Error Frame – 6 consecutive dominant bits – whenever it detects a problem with a message on the CAN bus. The fact that all messages much be confirmed or acknowledged by all nodes is a key reason that CAN provides highly reliable communication. After an Error Frame is sent, no other node will recognize the Message Frame as valid. The CAN hardware automatically detects five types of errors. Let’s start by looking at a bit error. A transmitting node always reads back the message it is sending. If it sees a different bit value on the bus than it sent – and that bit is not part of the arbitration field or in the acknowledgement field – it detects an error.