Identifying fault causes in the CAN network

HINT: For the low speed network, suitable places for disconnecting the network are at the steering wheel module (SWM), the driver information module (DIM) or the climate control module (CCM). 

In the event of an short-circuit between on of the CAN cables and voltage or ground, the fault can be localized disconnecting a control module that splits the CAN network. Readings can then be taken to determine on which side the fault is on the disconnected control module.

Connect an ohmmeter between the CAN cable and voltage supply respectively ground. Take readings from both ends of the CAN networks at the network junction. Twist and bend the cable harness to find any intermittent short-circuits. The resistance must be infinite or very high (more than 1 MΩ).

If a fault can be localized in one direction, split the network at a point further on in the CAN network in the direction that the fault was discovered and take a new reading. Try to locate the fault in this way.

HINT: A short-circuit between the CAN cables and supply voltage or ground may be in either the wiring or in a control module. 

Remedy the cables as necessary. If a fault is found on one control module, replace the control module.

Refer to Verification 

HINT: For the low speed network, suitable places for disconnecting the network are at the steering wheel module (SWM), the driver information module (DIM) or the climate control module (CCM). 

In the event of an open-circuit on, or short-circuit between the CAN cables, the fault can be localized by disconnecting a control module that splits the CAN network. Readings can then be taken to determine on which side the fault is on the disconnected control module.

Connect an ohmmeter between the CAN cables. Take readings from both ends of the CAN networks at the network junction. Twist and bend the cable harness to find any intermittent short-circuits. Resistance should be 120 Ω.

If a fault can be localized in one direction, split the network at a point further on in the CAN network in the direction that the fault was discovered and take a new reading. Try to locate the fault in this way.

Remedy the cables as necessary.

Refer to Verification