Circuit Description
Modules connected to the GMLAN High Speed serial data circuit monitor for serial
data communications on the GMLAN High Speed network during normal vehicle operation.
Operating information and commands are exchanged among the modules. Each module on
GMLAN High Speed 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 U0001 will be set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC U0001 Unassigned
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 High Speed 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
High Speed serial data circuits. |
| • | The module inhibits the setting of all other GMLAN High Speed 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
High Speed serial data circuits. Use the Scan Tool Does Not Communicate with High
Speed GMLAN Device procedure in order to isolate an intermittent condition. Refer
to
Scan Tool Does Not Communicate with High Speed GMLAN Device
. |
