DTC U0100-U0299 Diesel Engine
Circuit Description
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. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module. A module with a high speed GMLAN serial data circuits malfunction or which loses power during the current ignition cycle will have a Loss of Communication DTC set by other modules that depend on information from that failed module. If any of the high speed GMLAN circuits are shorted to battery voltage, ground or between them, no communication is possible on high speed GMLAN serial data bus, and a DTC U0073 is set.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC U0100 Lost Communication With Engine Control Module (ECM) |
| • | DTC U0101 Lost Communication With Transmission Control Module (TCM) |
| • | DTC U0106 Lost Communication With Glow Plug Control Module (GPCM) |
Conditions for Running the DTCs
| • | Voltage supplied to the modules is in the normal operating voltage range. |
| • | The engine is running. |
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received.
Action Taken When the DTC Sets
| • | The module uses a default value for the missing parameter. |
| • | The malfunction indicator lamp (MIL) will illuminate on the second consecutive ignition cycle that the diagnostic runs and fails, for the type B DTCs. For a detailed description about DTC types, refer to Powertrain Diagnostic Trouble Code (DTC) Type Definitions for the 6.6L (LLY) engine. |
Conditions for Clearing the MIL/DTC
The MIL/DTC clearing depends on DTC type. For information about DTC types, refer to Diagnostic Trouble Code (DTC) Types for the 6.6L (LLY) engine.
| • | DTC type B |
| - | The MIL clears after 3 ignition cycles when the malfunction is no longer present. |
| - | 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. |
| • | DTC type C |
| - | 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
| • | A poor connection at the inoperative module may cause this code to set. |
| • | An improperly powered module may cause this code to set. |
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
A total loss of communication on high speed GMLAN serial data link should be diagnosed first.
-
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 Communication Schematics Connector End View Reference: Master Electrical Component List | |||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||||||||||
Is DTC U0073 set as current? | Go to DTC U0073 | Go to Step 3 | |||||||||||||||||
3 |
Important: Use the DTC descriptor list in order to determine which module is not communicating on high speed GMLAN serial data bus.
Refer to the following:
Did you find and correct the condition? | Go to Step 9 | Go to Step 4 | ||||||||||||||||
4 |
Refer to the following:
Did you find and correct the condition? | Go to Step 9 | Go to Step 5 | ||||||||||||||||
5 | Test the high speed GMLAN serial data circuits of the module that is not communicating on high speed GMLAN serial data bus for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 6 | ||||||||||||||||
6 | Inspect the harness connectors of the module that is not communicating on high speed GMLAN serial data bus for poor connections and terminal tension at the following circuits:
Refer to the following:
| Go to Step 9 | Go to Step 7 | ||||||||||||||||
7 | Replace the module that is not communicating on high speed GMLAN serial data bus. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 8 | -- | ||||||||||||||||
8 |
Does the scan tool display any DTCs which do not begin with a "U"? | Go to Step 9 | |||||||||||||||||
9 | Select the Display DTCs function for 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 Step 10 | |||||||||||||||||
Did you complete the action? | System OK | -- | |||||||||||||||||
DTC U0100-U0299 HP2
Circuit Description
Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. There are two 120 ohm resistors between the GMLAN serial data (+) and (-) circuits. One is internal to the powertrain control module (PCM) and the other is internal to the energy storage control module (ESCM). When tested between the GMLAN serial data (+) and (-) circuits at the DLC with the ignition key OFF, normal resistance is 55-65 ohms.
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. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module. When a message that indicates the availability of the transmitter module is not received, the receiver module sets a DTC.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC U0111 Lost Communication With Energy Storage Control Module (ESCM) |
| • | DTC U0120 Lost Communication With Starter/Generator Control Module (SGCM) |
| • | DTC U0131 Lost Communication With Electro-Hydraulic Power Steering (EHPS) Module |
| • | DTC U0293 Lost Communication With Hybrid Control Module (HCM) |
Conditions for Running the DTCs
Voltage supplied to the modules is in the normal operating voltage range.
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received by powertrain control module (PCM) from one or more of the high speed GMLAN modules.
Action Taken When the DTC Sets
| • | The MIL may illuminate. |
| • | The Hybrid Engine Idle Off feature may not operate properly. |
Conditions for Clearing the MIL/DTC
| • | The MIL clears after 3 ignition cycles when the malfunction is no longer present. |
| • | 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
The following conditions may cause the DTC to set:
| • | A poor connection or terminal tension at a GMLAN module |
| • | An intermittent open on either high speed GMLAN serial data circuit |
| • | An open voltage or ground circuit to a module |
| • | An internal module malfunction |
| • | A short between the GMLAN serial data circuits |
| • | A short to voltage or ground on either of the GMLAN serial data circuits |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Data Communication Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views | ||||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||||||||||
2 |
Important: Use the DMM MIN/MAX function to capture intermittent conditions.
Is the resistance within the specified range? | 55-65 ohms | Go to Step 3 | Go to Step 11 | ||||||||||||||||
3 |
Does the scan tool communicate with any of the listed modules? | -- | Go to Step 8 | Go to Step 4 | ||||||||||||||||
4 |
Important: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. Test the high speed GMLAN serial data circuits at the data link connector (DLC) for:
Refer to the following: Did you find any of the above conditions? | -- | Go to Step 5 | Go to Step 8 | ||||||||||||||||
5 |
Does the short found at step 4 at DLC still exist? | -- | Go to Step 7 | Go to Step 6 | ||||||||||||||||
6 |
Important: If only PCM was disconnected on step 5, answer No at this step. Test the high speed GMLAN serial data circuits between the last 2 disconnected modules for the short found at step 4. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 7 | ||||||||||||||||
7 | Repair the high speed GMLAN serial data circuits between DLC and ESCM/SGCM for the short found in step 4. Refer to the following: Did you complete the repair? | -- | Go to Step 14 | -- | ||||||||||||||||
8 |
Important: Use the DTC Descriptors list in order to determine which module 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 14 | Go to Step 9 | ||||||||||||||||
9 |
Refer to the following:
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 | ||||||||||||||||
10 | Test the high speed GMLAN serial data circuits of the module that is not communicating for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 | ||||||||||||||||
|
Important: A circuit or module terminal tension is the likely fault. If a module does cause the malfunction, proceed to step 12. Repair the high speed GMLAN serial data (+) or (-) circuit as necessary. Did you find and correct the condition with a wiring repair? | -- | Go to Step 14 | Go to Step 12 | |||||||||||||||||
12 | Inspect the harness connectors of the module that is not communicating or is causing the malfunction for poor connections and terminal tension at the following circuits:
Refer to the following:
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 | ||||||||||||||||
13 | 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 14 | -- | ||||||||||||||||
14 |
Does the scan tool display any DTCs which do not begin with a "U"? | -- | Go to Step 15 | |||||||||||||||||
15 | Select the Display DTCs function for 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 Step 16 | |||||||||||||||||
16 |
Did you complete the action? | -- | System OK | -- | ||||||||||||||||
