Checking the traffic load on the CAN cables

Fig 1: Identifying Ignition ON

Courtesy of VOLVO CARS OF NORTH AMERICA.

• Connect the battery.
• Ignition on.

  Faults in the CAN network may be due to a control module sending faulty messages that disrupt normal communication. When messages are sent incorrectly, this results in a considerable increase in the amount of traffic on the CAN network. The load can be checked by reading the average value of the voltage on the CAN cables in relation to ground.

  The following applies for model year -2004: 

  Connect a voltmeter between CAN-L and ground. The voltage shall be approx. 2.3 V.

  Then connect a voltmeter between CAN-H and ground. The voltage shall be approx. 2.8 V.

  The following applies for model year 2004-: 

  Connect a voltmeter between CAN-L and ground. The voltage should be approx: 1.8-2.2 V

  Connect a voltmeter between CAN-H and ground. The voltage should be approx: 2.8-3.2 V

  NOTE:

  For vehicles of later model years, normal voltage values lie within a specific interval due to increased traffic between the control modules on the CAN network upon update of the electrical system.

  HINT: If possible, measure from the rear of the affected connectors so that they are not damaged. 

  Other information 

  • See Battery, disconnecting

Is the value OK? 

• YES 

  Refer to Information 

• NO 

  Refer to Identifying a control module in the CAN network