Identifying Fault Causes In The Can Network
- Disconnect a control module that disconnects the CAN network (a control module that has four terminals to 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 a short-circuit between one of the CAN cables and voltage or ground, the fault can be located by disconnecting a control module that disconnects the CAN network. Readings can then be taken to determine on which side of the disconnected control module the fault is located.
Connect an ohmmeter between the CAN cable and supply voltage or ground. Take readings at both ends of the CAN network where the network is disconnected. Twist and bend the cable harness to locate any intermittent short-circuits. The resistance must be infinite or very high (greater than 1MΩ).
If a fault can be localized in one direction, disconnect the network at a point further down on the CAN network in the direction in which the fault was discovered and repeat the reading. In this way, try to identify where in the network the fault might be located.
HINT: A short-circuit between the CAN cables and supply voltage or ground may be in either the wiring or in a control module.
Rectify the wiring as necessary. Replace the control module if the fault has been localized to a control module.
- Continue
See: VERIFICATION
- Disconnect a control module that disconnects the CAN network (a control module that has four terminals to 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 open-circuit or a short-circuit between the CAN cables, the fault can be localized by disconnecting a control module that disconnects the CAN network. Readings can then be taken to determine on which side of the disconnected control module the fault is located.
Connect an ohmmeter between the CAN cables. Take readings at both ends of the CAN network where the network is disconnected. Twist and bend the cable harness to locate any intermittent short-circuits. The resistance must be 120 ohm.
If a fault can be localized in one direction, disconnect the network at a point further down on the CAN network in the direction in which the fault was discovered and repeat the reading. In this way, try to identify where in the network the fault might be located.
Remedy the cables as necessary.
Was a fault detected?
- YES
See: VERIFICATION
- NO