Failure of the CAN-Bus cables

The following faults can occur to the CA-Bus wiring:

• CAN-H/L interrupted
• CAN-H/L shorted to battery voltage
• CAN-H/L shorted to ground
• CAN-H shorted to CAN-L
• Defective plug connections (damaged, corroded, or improperly crimped)

In each instance, the connected control units will store a fault due to the lack of information received over the CAN-Bus.

The term "Timeout"  this refers to a module not being able to communicate with another module on the bus. Each module on the CAN-Bus will attempt communication several times. If unsuccessful, the module will store a "Timeout" or "CAN-Bus" fault and determine that there is a problem with either the bus line or the module that it is trying to communicate with.

These types of faults may indicate a problem with the bus wiring, interference, missing data or failure of the communication module of an individual control unit.

Checking the CAN lines is carried out just like any other wiring. Perform continuity tests between the connections of different modules (all modules disconnected) without forgetting to make sure that the two CAN lines have not shorted to ground or to each other. It is recommended to use the "Wire Test" in "Preset Measurements" which is more sensitive than just a resistance check.

If Voltage level and the wire test are O.K, then looking at the communication signal may be useful.

The following are some examples of scope patterns that may be observed when checking the CAN-Bus.