Taking Reading On Cable In The Can Network (HS-Can)
- Ignition off
- Disconnect the battery negative lead.
- 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. See the appropriate service information for the relevant car model. 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
- Resistance between C3:47 and C3:48. Resistance should be 120 Ω.NOTE:
Measuring will only give value 120 Ω if the main circuit in the CAN-net is intact. If there is a short-circuit somewhere in the CAN-net (either main circuit or other branching) the resistance will be 0 Ω.
- The resistance between C3:48 and a connection to voltage as well as between C3:48 and a short-circuit to ground. The resistance shall be very high (more than 1 MΩ).
- The resistance between C3:47 and a connection to voltage as well as between C3:47 and a short-circuit to ground. The resistance shall be very high (more than 1 MΩ).
HINT: Any short-circuit detected on the CAN-net may be on the main circuit or on any branching running out to some control modules. 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
- Resistance between C3:47 and C3:48. Resistance should be 120 Ω.
Was a fault detected?
- YES
Refer to VERIFICATION
- NO