Checking The Traffic Load On The Can Cables

Fig 1: Identifying Ignition ON

Courtesy of VOLVO CARS CORPORATION

• Connect the central electronic module (CEM) to the breakout box
• Connect the battery.

  see BATTERY, DISCONNECTING

• Ignition on.
  NOTE:

  When the adapter cable harness and the central electronic module (CEM) have been connected, there is access to both sides of the CAN network (both LS-CAN and HS-CAN). There will also be traffic on both networks. Be careful to check the terminals between which the readings are to be taken so that the intended reading is not taken on the wrong network.

  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. Check the load by measuring the average voltage value on the CAN cables in relation to ground.

  Check as follows:

  • Measure the voltage between terminal #B9 (#9) (LS-CAN-L) and ground. The voltage must be approximately 2.3 V
  • Measure the voltage between terminal #B8 (#8) (LS-CAN-H) and ground. The voltage must be approximately 2.8 V.

Is the value OK? 

• YES 

  Refer to INFORMATION 

• NO 

  Refer to IDENTIFYING A CONTROL MODULE IN THE CAN NETWORK