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June 2013
Electrical Systems Operation & Diagnosis Module (602)
High Speed CAN Signal Construction
When reviewing the service manual you will find references to High Speed CAN and Low Speed
CAN. Each of these has a CAN-High wire and a CAN-Low wire. The differences in operating speed
have already been discussed and now the construction of the two circuits needs to be understood
before fully understanding operational differences.
High Speed CAN (ARTWORK)
When the logic value of the High Speed CAN is 1 there is no potential difference between the
voltage levels of CAN High and CAN Low. The level of both signals is 2.5 volts. When the logic
value changes to a 0 the voltage level of both signals move away from each other. CAN High will
be 3.5 volts and CAN Low will be 1.4 volts. This operation helps to ensure that there is no electrical
interference and the signals received by the various components of the LAN are receiving genuine
signals.
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