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Identifying A Control Module In The Can Network

If the load on the CAN network is too high, this may be due to a control module transmitting faulty messages on the CAN network. This is called a disruptive control module. The fault may also be due to an intermittent short-circuit to supply voltage or ground in one of the CAN cables. This results in the control modules on the CAN network starting to send faulty messages. An intermittent short-circuit may occur without a diagnostic trouble code (DTC) being stored by any of the control modules.

NOTE:

It is not necessarily the control module that has set the diagnostic trouble code that communicates incorrectly. Faulty messages can come from any control module in the same section of the CAN network. However, faulty communication in one network cannot affect the communication on the other network. n other words, faulty communication on MS-CAN cannot disrupt communication on HS-CAN and vice versa.

Check communication/load on CAN-net by measuring voltage between C1:49 and C1:50. he voltage's average value shall be approx. 0.5 V (permitted is 0.4 to 0.6 V). n case of communication error, the voltage is approx. 0.7 V and higher.

In order to identify which control module is communicating incorrectly, cut the power supply to one control module at a time. Check the voltage in the CAN cables again. The easiest way to cut the power supply is to remove the fuse(s) for the relevant control module. Continue until the voltage between the CAN cables drops to approximately 0.5 V.

HINT: When the suspected control module has been identified, connect and disconnect the supply voltage to the control module a number of times to verify that the fault appears and disappears. Switch off the ignition between each check. 

NOTE:

Do not cut the power to the central electronic module (CEM) unless it is the last control module left to check.

The control module that is communicating incorrectly must be replaced.

NOTE:

Following a fault involving control modules that disrupt communication, other control modules may operate in Limp-Home mode (i.. hey work but with limited functionality) even after switching the ignition off and on a number of times. To remedy this, disconnect and reconnect the battery negative terminal to restore the control modules to normal function.

Remedy as necessary.

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