GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The GMLAN serial data circuits are controller area network (CAN) high speed serial data buses used to communicate information between the control modules. Typical data transmission speeds must be high enough to ensure that a required real-time response is maintained. This vehicle contains a High speed 2-wire circuit . Refer to Data Link Communications Description and Operation for the complete description of the buses used on this vehicle. The GMLAN serial data circuits also communicate directly to the data link connector (DLC). Messages are interpreted by the externally connected CANdi module which acts as a transceiver for the scan tool.

Modules connected to the GMLAN serial data circuits monitor communications during normal vehicle operation, where operation information is exchanged among the modules. All the modules on the GMLAN networks, maintain 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 DTC U2100 will result.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC U2100 Controller Area Network (CAN) Bus Communication

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description in Vehicle DTC Information.

DTC Symptom

DTC Symptom Descriptor

00

No Additional Information

Conditions for Running the DTCs

    • Supply voltage to the modules are in the normal operating range.
    • The vehicle is in the RUN power mode.

Conditions for Setting the DTC

The module setting the DTC has attempted to establish communications on the GMLAN circuits for more than 7 times.

Action Taken When the DTCs Sets

    • The module suspends all message transmission.
    • The module uses default values for all parameters received on the serial data circuits.
    • The module inhibits the setting of all other 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

    • This DTC cannot be retrieved with a current status. Diagnosis of a current DTC can only be accomplished by referring to Scan Tool Does Not Communicate with High Speed GMLAN Device
    • An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Refer to Scan Tool Does Not Communicate with High Speed GMLAN Devicein order to isolate an intermittent condition.