Taking Reading On Cable In The Can Network (HS-Can)

Fig 1: Identifying Ignition In Off Position And Disconnecting Negative Cable From Battery

Courtesy of VOLVO CARS CORPORATION

• Disconnect the battery negative lead.
  NOTE:

  see BATTERY, DISCONNECTING

• Remove the central electronic module (CEM)
• Connect the breakout box to the cable harness for the central electronic module (CEM). Do not connect the central electronic module (CEM).

  HINT: Where a breakout box cannot be used, take readings from the rear of the affected connectors if possible. This prevents terminal pins and socket housings being damaged. 

  Disconnect the CAN network to make it easier to locate a fault. A suitable point to disconnect the network is at the central electronic module (CEM). Fault-tracing therefore starts from the central electronic module (CEM).

  Take resistance readings across the following terminals. Various readings will be obtained due to the structure of the network. Twist the cable harness and work the connectors at accessible points along the cable harness in order to check whether the resistance changes during each measurement. This method can be used to detect intermittent short-circuits or open-circuits.

  NOTE:

  The following resistance readings only measure the main arteries in the high speed network, not the junctions that exist for some control modules. If an open-circuit is suspected in a cable, or a short-circuit is suspected in one of its junctions, the connector at the control module for this junction must be disconnected and the reading taken from there.

  Take the following readings 

  • Between terminals #G14 (#14) and #G15 (#15). Check the resistance. The resistance must be approximately 120 Ω.
  • Between terminal #G14 (#14) and a terminal for supply voltage, and between terminal #G14 (#14) and a terminal for ground. Check the resistance. The resistance must be infinite or very high in both cases (higher than 1 MΩ)
  • Between terminal #G15 (#15) and a terminal for supply voltage, and between terminal #G15 (#15) and a terminal for ground. Check the resistance. The resistance must be infinite or very high in both cases (higher than 1 MΩ)
  • Between terminals #F14 (#14) and #F16 (#16). Check the resistance. The resistance must be approximately 120 Ω.
  • Between terminal #F14 (#14) and a terminal for supply voltage, and between terminal #F14 (#14) and a terminal for ground. Check the resistance. The resistance must be infinite or very high in both cases (higher than 1 MΩ)
  • Between terminal #F16 (#16) and a terminal for supply voltage, and between terminal #F16 (#16) and a terminal for ground. Check the resistance. The resistance must be infinite or very high in both cases (higher than 1 MΩ).

  HINT: If a fault is found, try to disconnect the junction with the fault at a point further forward. Try to locate the fault in this way. 

  Remedy as necessary.

  Other information 

  • see CONNECTING THE BREAKOUT BOX (2008-2012)
  • see SIGNAL DESCRIPTION CENTRAL ELECTRONIC MODULE (CEM)
  • see CHECKING WIRING AND TERMINALS

Was a fault detected? 

• YES 

  Refer to VERIFICATION 

• NO 

  Refer to CHECKING THE TRAFFIC LOAD ON THE CAN CABLES