U2100

DTC U2100

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
This diagnostic procedure supports the following DTC:
DTC U2100 Controller Area Network (CAN) Bus Communication




This vehicle has DTCs which include DTC Symptoms. The DTC symptom descriptions for symptoms 71 and 72 are exceptions for this vehicle and differ from what is described on DTC Symptom Description. For more information on DTC Symptoms, refer to DTC Symptom Description. DTC Symptom Description

CONDITIONS FOR RUNNING THE DTC
- 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 DTC 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 for the respective bus.

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

U2100 72
- This DTC cannot be retrieved with a current status. Diagnosis of a 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.

U2100 71 and U2100 00
These DTCs can be retrieved from instrument panel module (IPM) with a current status. Refer to the table to diagnose it. DTC U2100 00 can be retrieved with a current status only it was set for low speed GMLAN link. If set for high speed GMLAN link, see U2100 72.

TEST DESCRIPTION

Step 1 - Step 7:

Step 8 - Step 13:

Step 14 - Step 18:

The numbers below refer to the step numbers on the diagnostic table.
4. The low speed serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wire for a short, make sure there is not a module connected to the wire being tested. This test isolates the splice pack SP303 serial data circuits.
7. The low speed serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wire for a short, make sure there is not a module connected to the wire being tested. This test isolates the splice pack SP300 serial data circuits.
10. This test isolates the splice pack SP201 serial data circuits.
15. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
16. The communication malfunction may have prevented diagnosis of the customer complaint.