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.
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 | DTC Symptom Descriptor |
---|---|
00 | No Additional Information |
71 | Low Speed Bus Error |
72 | High Speed Bus Error |
• | Voltage supplied to the module is in the normal operating voltage range. |
• | The vehicle power mode requires serial data communication to occur. |
A certain number of no valid transmitted messages on the GMLAN serial data circuits are detected by the module.
• | 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. |
• | A current DTC clears when the malfunction is no longer present. |
• | When the ignition cycle counter has reached the newly set threshold and no trouble occurs repeatedly, the history DTC will be cleared. |
• | 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 . |
These DTCs can be retrieved from instrument panel module (IPM) with a current status. Refer to the table below 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.
The numbers below refer to the step numbers on the diagnostic table.
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.
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.
This test isolates the splice pack SP201 serial data circuits.
If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
The communication malfunction may have prevented diagnosis of the customer complaint.
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: Data Communication Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Is U2100 71 and/or U2100 00 set as current? | Go to Step 4 | Go to Step 3 |
3 |
Important: Turn ON the ignition, with the engine OFF to test a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions Test the low speed GMLAN serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following: Did you find and correct the condition? | Go to Step 18 | -- |
Is U2100 71 and/or U2100 00 set as current? | Go to Step 7 | Go to Step 5 | |
5 | Repeat the following steps on the low speed GMLAN serial data circuits connected to the splice pack SP303 until the concern is located:
Is U2100 71 and/or U2100 00 set as current? | Go to Step 6 | -- |
6 |
Did you find and correct the condition? | Go to Step 15 | Go to Step 14 |
Is U2100 71 and/or U2100 00 set as current? | Go to Step 10 | Go to Step 8 | |
8 | Repeat the following steps on the low speed GMLAN serial data circuits connected to the splice pack SP300 until the concern is located:
Is U2100 71 and/or U2100 00 set as current? | Go to Step 9 | -- |
9 |
Did you find and correct the condition? | Go to Step 15 | Go to Step 14 |
Is U2100 71 and/or U2100 00 set as current? | Go to Step 13 | Go to Step 11 | |
11 | Repeat the following steps on the low speed GMLAN serial data circuits connected to the splice pack SP201 until the concern is located:
Is U2100 71 and/or U2100 00 set as current? | Go to Step 13 | -- |
12 |
Did you find and correct the condition? | Go to Step 15 | Go to Step 14 |
13 |
Did you find and correct the condition? | Go to Step 15 | Go to Step 14 |
14 | Replace the last disconnected module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 15 | -- |
Is there any DTC which begin with a U and a current status? | Go to Step 16 | ||
Is there any DTC which does not begin with a U recorded? | Go to Step 17 | ||
17 | Have you any DTCs not diagnosed? | Go to Step 18 | Go to Step 15 |
18 | Clear the DTCs with the scan tool. Is the operation completed? | System OK | -- |