Circuit Description
Modules connected to the GMLAN serial data circuit monitor for serial
data communications on the GMLAN network during normal vehicle operation.
Operating information and commands are exchanged among the modules. Each module
on GMLAN network maintains a transmit error counter (TEC) and
a receive error counter (REC). The counter values increase with detected errors
and will decrease with error-free messages. If the TEC value exceeds 255 the
controller removes itself from the network and a DTC U2100 will be set.
Conditions for Running the DTCs
| • | Voltage supplied to the module is in the normal operating voltage
range. |
| • | The vehicle power mode requires serial data communication to occur. |
Conditions for Setting the DTC
A certain number of no valid transmitted messages on the GMLAN serial
data circuits are detected by the module.
Action Taken When the DTCs Sets
| • | The module suspends all message transmission. |
| • | The module uses default values for all parameters received on
the GMLAN serial data circuits. |
| • | The module inhibits the setting of all other GMLAN communication
DTCs. |
Conditions for Clearing the DTC
| • | A current DTC clears when the malfunction is no longer present. |
| • | A history DTC clears when the module ignition cycle counter reaches
the reset threshold, without a repeat of the malfunction. |
Diagnostic Aids
| • | An intermittent condition is likely to be caused by a short on the GMLAN
serial data circuits. Use the Scan Tool Does Not Communicate with CAN Device
procedure in order to isolate an intermittent condition. Refer to
Scan Tool Does Not Communicate with CAN Device
. |
