GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Equinox 🢒 Power and Signal Distribution 🢒 Data Communications 🢒 DTC U2104

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.

DTC Descriptor

DTC U2104 : Controller Area Network (CAN) Bus Reset Counter Overrun

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. The engine will not start when there is a total malfunction of the high speed GMLAN serial data circuits while the engine is not running. The following conditions may cause a total loss of high speed GMLAN data communication:

    • A short between high speed GMLAN (+) and high speed GMLAN (-) circuits
    • Any of the high speed GMLAN serial data circuits shorted to ground or voltage
    • A module internal malfunction that causes a short to voltage or ground on the high speed GMLAN circuits
    • Any of the high speed GMLAN serial data circuits open

Action Taken When the DTCs Sets
    • The module suspends all message transmission.
    • The module uses default values for all parameters received on the high speed GMLAN serial data circuits.
    • The module inhibits the setting of all other high speed 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
    • This DTC cannot be retrieved with a current status. Diagnosis of current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with high speed GMLAN Device. Refer to Scan Tool Does Not Communicate with High Speed GMLAN Device .
    • An intermittent condition is likely to be caused by a short on the high speed high speed GMLAN 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 .