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 sending incorrect messages on the CAN network (known as a disruptive control module). The malfunction may also be due to an intermittent short-circuit to voltage or ground in one of the CAN-cables. This results in the control modules on the CAN-network starting to send incorrect messages. The malfunctions can occur without a diagnostic trouble code (DTC) being stored by the control modules. The voltage can be measured between the CAN-cables in order to check the load on the CAN-network.
It is not necessarily the control module(s) that stored the diagnostic trouble code (DTC) that is communicating incorrectly. Incorrect messages can come from any control module in the same section of the CAN-network. However, incorrect communication in one network cannot affect the communication on the other network. In other words, incorrect communication on the LS-CAN cannot disrupt communication on the HS-CAN, and vice versa.
Check the communication/load on the CAN-network by measuring the voltage between #B45 (#C45) and #B58 (#C58). The average value of the voltage shall be approx. 0.5 V (0.4-0.6 V). In case of malfunctioning communication, the voltage is at approx. 0.7 V and above.
To identify which control module is responsible for the incorrect communication, one can disconnect the voltage feed to each control module in turn and re-check the voltage on the CAN-cables. The voltage feed is most easily disconnected by removing the fuse/fuses for the particular control module. Continue until the voltage between the CAN-cables drops to about 0.5 V.
When connecting and disconnecting individual control modules, other diagnostic trouble codes (DTCs) may be stored in certain control modules.
HINT: When a suspected control module is identified, connect and disconnect the voltage feed several times to verify that the malfunction appears and disappears. Turn off the ignition between each check.
Do not cut the voltage to the central electronic module (CEM) unless it is the last control module left to check.
A control module which communicates incorrectly must be replaced. See Repair and installation/Removal, replacement and installation.
Following a malfunction involving control modules that disrupt communication, other control modules may remain in Limp-Home mode (that is, they work but with limited functionality) even after the ignition has been turned off and on a number of times. To remedy this, disconnect and reconnect the battery's minus terminal to restore the control modules to normal function.
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Refer to Verification