Important: For DTC U2153 refer to DTC U2153 .
Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module.
This diagnostic procedure supports the following DTCs:
• | DTC U2105 Lost Communication With Engine Control Module (ECM) |
• | DTC U2106 Lost Communication With Transmission Control Module (TCM) |
• | DTC U2107 Lost Communication With Body Control Module (BCM) |
• | DTC U2108 Lost Communication With Electronic Brake Control Module (EBCM) |
• | DTC U2112 Lost Communication With Electronic Suspension Control (ESC) Module |
• | DTC U2144 Lost Communication With Distance Sensing and Cruise Control (DSCC) Module |
DTC Symptom | DTC Symptom Descriptor |
---|---|
00 | No Additional Information |
• | Voltage supplied to the modules is in the normal operating voltage range. |
• | The vehicle power mode requires serial data communication to occur. |
• | The DTC U2100 does not have a current status. |
A supervised periodic message that includes the transmitter module availability has not been received.
The module uses a default value for the missing parameter.
• | 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. |
• | A poor connection at the inoperative module may cause this code to set. |
• | An improperly powered module may cause this code to set. |
The numbers below refer to the step numbers on the diagnostic table:
If body control module (BCM) detects an open in its class 2 circuit, the remote control door lock (RCDLR) takes control of the run/crank relay.
A power moding code needs to be diagnosed first.
The scan tool communicate with OnStar® via class 2, so for high speed GMLAN data link diagnostic the OnStar® will not be considered.
The module which was not communicating due to an open in the high speed GMLAN serial data circuits may have set Loss of Communication DTCs for those modules that it was monitoring.
The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.
Step | Action | Yes | No | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Data Link Connector Schematics Connector End View Reference: Master Electrical Component List | |||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||||
Does the scan tool display OFF? | Go to Step 3 | Go to Step 5 | |||||||||||
Retrieve DTCs from remote control doorlock receiver (RCDLR) module. Is the DTC B1440 set? | Go to DTC B1440 | Go to Step 4 | |||||||||||
4 |
Did you find and correct the condition? | Go to Step 18 | Go to Step 15 | ||||||||||
Attempt to communicate with electronic suspension control (ESC) module. Were you able to communicate with ESC module? | Go to Step 10 | Go to Step 6 | |||||||||||
6 |
Were you able to communicate with ESC module? | Go to Step 7 | Go to Step 9 | ||||||||||
7 | Test the high speed GMLAN serial data circuits of the OnStar® for poor connections. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 19 | Go to Step 8 | ||||||||||
8 | Replace the OnStar®. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 19 | -- | ||||||||||
9 |
Did you find and correct the condition? | Go to Step 19 | Go to Step 10 | ||||||||||
10 |
Important:: Use the DTC list from the DTC Descriptors to determine the closest module to dta link connector (DLC) which is not communicating. Test the following circuits of the module that is not communicating, for an open or a short to ground:
Refer to the following:
Did you find and correct the condition? | Go to Step 19 | Go to Step 11 | ||||||||||
11 |
Did you find and correct the condition? | Go to Step 19 | Go to Step 12 | ||||||||||
12 | Test the high speed GMLAN serial data circuits of the module that is not communicating, for an open. Refer to the following:
Did you find and correct the condition? | Go to Step 17 | Go to Step 13 | ||||||||||
13 | Test the following circuits of the module that is not communicating, for poor connections:
Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 19 | Go to Step 14 | ||||||||||
14 | Replace the module that is not communicating. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 19 | -- | ||||||||||
15 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 19 | Go to Step 16 | ||||||||||
16 | Replace the BCM. Refer to Body Control Module Replacement for replacement, setup, and programming. Did you complete the replacement? | Go to Step 19 | -- | ||||||||||
Does the scan tool display any DTCs which do not begin with a "U"? | Go to the Diagnostic System Check - Vehicle | Go to Step 18 | |||||||||||
18 | Use the scan tool in order to clear the DTCs. Did you complete the action? | Go to Step 19 | -- | ||||||||||
Retrieve DTCs from the modules which had the Loss of Communications DTC set. Does the scan tool display any DTCs which do not begin with a "U"? | Go to the Diagnostic System Check - Vehicle | Go to Step 20 | |||||||||||
20 |
Did you complete the action? | System OK | -- |