U1064
Diagnostic Chart:
Schematic:
The Class II serial data circuit 18O7 is used to communicate information between modules (for example the body control module [BCM] and the powertrain control module [PCM]).
Contained in each modules memory is a list of serial data messages that are important and should be received by the module. Also, contained are the default actions to be taken by the module, if one of the important messages is not received in time. One of those important messages is the state of health (SOH) message. This message is sent by a module (if no other message needs to be sent) to let all the other modules on the serial data link know the sending module is working correctly.
Each time the ignition is turned On, all the modules on the Class II serial data circuit first "learn" the other modules connected to the Class II serial data circuit. Modules are able to "learn" the other modules on the serial data circuit because each of the important messages contains a source identifier as part of the message. This process of "learning" by a module to know if it has lost communication with a specific module on the Class II data circuit.
DTC Parameters
The DTC is set when ignition is turned On and the electronic module previously learned the source identifier of a specific module and then expects to receive a message from the same module and does not receive it.
^ Ignition switch is turned On.
^ Class II serial data communications was lost with the BCM.
^ This code can be set by the SDM and PCM, and EBTCM.
Diagnostic AIDS
^ Check for poor connection at the control module. Inspect harness connectors for backed out terminals, improper terminal mating, broken connector locks, improperly formed or damaged terminals and poor terminal to wire connection (terminal crimped over wire insulation and not conductors).
^ Inspect wiring harness for damage. Check for broken or chaffed insulation.
^ Review all fail information where available, as this may assist in determining the conditions when the fault occurs.
^ If fault is suspected to be intermittent, wiggling harness wiring may help in locating fault.